FFmpeg Filters Documentation

Table of Contents

1 Description

This document describes filters, sources, and sinks provided by the libavfilter library.

2 Filtering Introduction

Filtering in FFmpeg is enabled through the libavfilter library.

In libavfilter, a filter can have multiple inputs and multiple outputs. To illustrate the sorts of things that are possible, we consider the following filtergraph.

                [main]
input --> split ---------------------> overlay --> output
            |                             ^
            |[tmp]                  [flip]|
            +-----> crop --> vflip -------+

This filtergraph splits the input stream in two streams, then sends one stream through the crop filter and the vflip filter, before merging it back with the other stream by overlaying it on top. You can use the following command to achieve this:

ffmpeg -i INPUT -vf "split [main][tmp]; [tmp] crop=iw:ih/2:0:0, vflip [flip]; [main][flip] overlay=0:H/2" OUTPUT

The result will be that the top half of the video is mirrored onto the bottom half of the output video.

Filters in the same linear chain are separated by commas, and distinct linear chains of filters are separated by semicolons. In our example, crop,vflip are in one linear chain, split and overlay are separately in another. The points where the linear chains join are labelled by names enclosed in square brackets. In the example, the split filter generates two outputs that are associated to the labels [main] and [tmp].

The stream sent to the second output of split, labelled as [tmp], is processed through the crop filter, which crops away the lower half part of the video, and then vertically flipped. The overlay filter takes in input the first unchanged output of the split filter (which was labelled as [main]), and overlay on its lower half the output generated by the crop,vflip filterchain.

Some filters take in input a list of parameters: they are specified after the filter name and an equal sign, and are separated from each other by a colon.

There exist so-called source filters that do not have an audio/video input, and sink filters that will not have audio/video output.

3 graph2dot

The graph2dot program included in the FFmpeg tools directory can be used to parse a filtergraph description and issue a corresponding textual representation in the dot language.

Invoke the command:

graph2dot -h

to see how to use graph2dot.

You can then pass the dot description to the dot program (from the graphviz suite of programs) and obtain a graphical representation of the filtergraph.

For example the sequence of commands:

echo GRAPH_DESCRIPTION | \
tools/graph2dot -o graph.tmp && \
dot -Tpng graph.tmp -o graph.png && \
display graph.png

can be used to create and display an image representing the graph described by the GRAPH_DESCRIPTION string. Note that this string must be a complete self-contained graph, with its inputs and outputs explicitly defined. For example if your command line is of the form:

ffmpeg -i infile -vf scale=640:360 outfile

your GRAPH_DESCRIPTION string will need to be of the form:

nullsrc,scale=640:360,nullsink

you may also need to set the nullsrc parameters and add a format filter in order to simulate a specific input file.

4 Filtergraph description

A filtergraph is a directed graph of connected filters. It can contain cycles, and there can be multiple links between a pair of filters. Each link has one input pad on one side connecting it to one filter from which it takes its input, and one output pad on the other side connecting it to one filter accepting its output.

Each filter in a filtergraph is an instance of a filter class registered in the application, which defines the features and the number of input and output pads of the filter.

A filter with no input pads is called a "source", and a filter with no output pads is called a "sink".

4.1 Filtergraph syntax

A filtergraph has a textual representation, which is recognized by the -filter/-vf/-af and -filter_complex options in ffmpeg and -vf/-af in ffplay, and by the avfilter_graph_parse_ptr() function defined in libavfilter/avfilter.h.

A filterchain consists of a sequence of connected filters, each one connected to the previous one in the sequence. A filterchain is represented by a list of ","-separated filter descriptions.

A filtergraph consists of a sequence of filterchains. A sequence of filterchains is represented by a list of ";"-separated filterchain descriptions.

A filter is represented by a string of the form: [in_link_1]...[in_link_N]filter_name=arguments[out_link_1]...[out_link_M]

filter_name is the name of the filter class of which the described filter is an instance of, and has to be the name of one of the filter classes registered in the program. The name of the filter class is optionally followed by a string "=arguments".

arguments is a string which contains the parameters used to initialize the filter instance. It may have one of two forms:

  • A ’:’-separated list of key=value pairs.
  • A ’:’-separated list of value. In this case, the keys are assumed to be the option names in the order they are declared. E.g. the fade filter declares three options in this order – type, start_frame and nb_frames. Then the parameter list in:0:30 means that the value in is assigned to the option type, 0 to start_frame and 30 to nb_frames.
  • A ’:’-separated list of mixed direct value and long key=value pairs. The direct value must precede the key=value pairs, and follow the same constraints order of the previous point. The following key=value pairs can be set in any preferred order.

If the option value itself is a list of items (e.g. the format filter takes a list of pixel formats), the items in the list are usually separated by ‘|’.

The list of arguments can be quoted using the character ‘'’ as initial and ending mark, and the character ‘\’ for escaping the characters within the quoted text; otherwise the argument string is considered terminated when the next special character (belonging to the set ‘[]=;,’) is encountered.

The name and arguments of the filter are optionally preceded and followed by a list of link labels. A link label allows one to name a link and associate it to a filter output or input pad. The preceding labels in_link_1 ... in_link_N, are associated to the filter input pads, the following labels out_link_1 ... out_link_M, are associated to the output pads.

When two link labels with the same name are found in the filtergraph, a link between the corresponding input and output pad is created.

If an output pad is not labelled, it is linked by default to the first unlabelled input pad of the next filter in the filterchain. For example in the filterchain

nullsrc, split[L1], [L2]overlay, nullsink

the split filter instance has two output pads, and the overlay filter instance two input pads. The first output pad of split is labelled "L1", the first input pad of overlay is labelled "L2", and the second output pad of split is linked to the second input pad of overlay, which are both unlabelled.

In a filter description, if the input label of the first filter is not specified, "in" is assumed; if the output label of the last filter is not specified, "out" is assumed.

In a complete filterchain all the unlabelled filter input and output pads must be connected. A filtergraph is considered valid if all the filter input and output pads of all the filterchains are connected.

Libavfilter will automatically insert scale filters where format conversion is required. It is possible to specify swscale flags for those automatically inserted scalers by prepending sws_flags=flags; to the filtergraph description.

Here is a BNF description of the filtergraph syntax:

NAME             ::= sequence of alphanumeric characters and '_'
LINKLABEL        ::= "[" NAME "]"
LINKLABELS       ::= LINKLABEL [LINKLABELS]
FILTER_ARGUMENTS ::= sequence of chars (possibly quoted)
FILTER           ::= [LINKLABELS] NAME ["=" FILTER_ARGUMENTS] [LINKLABELS]
FILTERCHAIN      ::= FILTER [,FILTERCHAIN]
FILTERGRAPH      ::= [sws_flags=flags;] FILTERCHAIN [;FILTERGRAPH]

4.2 Notes on filtergraph escaping

Filtergraph description composition entails several levels of escaping. See (ffmpeg-utils)the "Quoting and escaping" section in the ffmpeg-utils(1) manual for more information about the employed escaping procedure.

A first level escaping affects the content of each filter option value, which may contain the special character : used to separate values, or one of the escaping characters \'.

A second level escaping affects the whole filter description, which may contain the escaping characters \' or the special characters [],; used by the filtergraph description.

Finally, when you specify a filtergraph on a shell commandline, you need to perform a third level escaping for the shell special characters contained within it.

For example, consider the following string to be embedded in the drawtext filter description text value:

this is a 'string': may contain one, or more, special characters

This string contains the ' special escaping character, and the : special character, so it needs to be escaped in this way:

text=this is a \'string\'\: may contain one, or more, special characters

A second level of escaping is required when embedding the filter description in a filtergraph description, in order to escape all the filtergraph special characters. Thus the example above becomes:

drawtext=text=this is a \\\'string\\\'\\: may contain one\, or more\, special characters

(note that in addition to the \' escaping special characters, also , needs to be escaped).

Finally an additional level of escaping is needed when writing the filtergraph description in a shell command, which depends on the escaping rules of the adopted shell. For example, assuming that \ is special and needs to be escaped with another \, the previous string will finally result in:

-vf "drawtext=text=this is a \\\\\\'string\\\\\\'\\\\: may contain one\\, or more\\, special characters"

5 Timeline editing

Some filters support a generic enable option. For the filters supporting timeline editing, this option can be set to an expression which is evaluated before sending a frame to the filter. If the evaluation is non-zero, the filter will be enabled, otherwise the frame will be sent unchanged to the next filter in the filtergraph.

The expression accepts the following values:

t

timestamp expressed in seconds, NAN if the input timestamp is unknown

n

sequential number of the input frame, starting from 0

pos

the position in the file of the input frame, NAN if unknown

w
h

width and height of the input frame if video

Additionally, these filters support an enable command that can be used to re-define the expression.

Like any other filtering option, the enable option follows the same rules.

For example, to enable a blur filter (smartblur) from 10 seconds to 3 minutes, and a curves filter starting at 3 seconds:

smartblur = enable='between(t,10,3*60)',
curves    = enable='gte(t,3)' : preset=cross_process

6 Audio Filters

When you configure your FFmpeg build, you can disable any of the existing filters using --disable-filters. The configure output will show the audio filters included in your build.

Below is a description of the currently available audio filters.

6.1 acompressor

A compressor is mainly used to reduce the dynamic range of a signal. Especially modern music is mostly compressed at a high ratio to improve the overall loudness. It’s done to get the highest attention of a listener, "fatten" the sound and bring more "power" to the track. If a signal is compressed too much it may sound dull or "dead" afterwards or it may start to "pump" (which could be a powerful effect but can also destroy a track completely). The right compression is the key to reach a professional sound and is the high art of mixing and mastering. Because of its complex settings it may take a long time to get the right feeling for this kind of effect.

Compression is done by detecting the volume above a chosen level threshold and dividing it by the factor set with ratio. So if you set the threshold to -12dB and your signal reaches -6dB a ratio of 2:1 will result in a signal at -9dB. Because an exact manipulation of the signal would cause distortion of the waveform the reduction can be levelled over the time. This is done by setting "Attack" and "Release". attack determines how long the signal has to rise above the threshold before any reduction will occur and release sets the time the signal has to fall below the threshold to reduce the reduction again. Shorter signals than the chosen attack time will be left untouched. The overall reduction of the signal can be made up afterwards with the makeup setting. So compressing the peaks of a signal about 6dB and raising the makeup to this level results in a signal twice as loud than the source. To gain a softer entry in the compression the knee flattens the hard edge at the threshold in the range of the chosen decibels.

The filter accepts the following options:

level_in

Set input gain. Default is 1. Range is between 0.015625 and 64.

threshold

If a signal of second stream rises above this level it will affect the gain reduction of the first stream. By default it is 0.125. Range is between 0.00097563 and 1.

ratio

Set a ratio by which the signal is reduced. 1:2 means that if the level rose 4dB above the threshold, it will be only 2dB above after the reduction. Default is 2. Range is between 1 and 20.

attack

Amount of milliseconds the signal has to rise above the threshold before gain reduction starts. Default is 20. Range is between 0.01 and 2000.

release

Amount of milliseconds the signal has to fall below the threshold before reduction is decreased again. Default is 250. Range is between 0.01 and 9000.

makeup

Set the amount by how much signal will be amplified after processing. Default is 2. Range is from 1 and 64.

knee

Curve the sharp knee around the threshold to enter gain reduction more softly. Default is 2.82843. Range is between 1 and 8.

link

Choose if the average level between all channels of input stream or the louder(maximum) channel of input stream affects the reduction. Default is average.

detection

Should the exact signal be taken in case of peak or an RMS one in case of rms. Default is rms which is mostly smoother.

mix

How much to use compressed signal in output. Default is 1. Range is between 0 and 1.

6.2 acrossfade

Apply cross fade from one input audio stream to another input audio stream. The cross fade is applied for specified duration near the end of first stream.

The filter accepts the following options:

nb_samples, ns

Specify the number of samples for which the cross fade effect has to last. At the end of the cross fade effect the first input audio will be completely silent. Default is 44100.

duration, d

Specify the duration of the cross fade effect. See (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax. By default the duration is determined by nb_samples. If set this option is used instead of nb_samples.

overlap, o

Should first stream end overlap with second stream start. Default is enabled.

curve1

Set curve for cross fade transition for first stream.

curve2

Set curve for cross fade transition for second stream.

For description of available curve types see afade filter description.

6.2.1 Examples

  • Cross fade from one input to another:
    ffmpeg -i first.flac -i second.flac -filter_complex acrossfade=d=10:c1=exp:c2=exp output.flac
    
  • Cross fade from one input to another but without overlapping:
    ffmpeg -i first.flac -i second.flac -filter_complex acrossfade=d=10:o=0:c1=exp:c2=exp output.flac
    

6.3 adelay

Delay one or more audio channels.

Samples in delayed channel are filled with silence.

The filter accepts the following option:

delays

Set list of delays in milliseconds for each channel separated by ’|’. At least one delay greater than 0 should be provided. Unused delays will be silently ignored. If number of given delays is smaller than number of channels all remaining channels will not be delayed.

6.3.1 Examples

  • Delay first channel by 1.5 seconds, the third channel by 0.5 seconds and leave the second channel (and any other channels that may be present) unchanged.
    adelay=1500|0|500
    

6.4 aecho

Apply echoing to the input audio.

Echoes are reflected sound and can occur naturally amongst mountains (and sometimes large buildings) when talking or shouting; digital echo effects emulate this behaviour and are often used to help fill out the sound of a single instrument or vocal. The time difference between the original signal and the reflection is the delay, and the loudness of the reflected signal is the decay. Multiple echoes can have different delays and decays.

A description of the accepted parameters follows.

in_gain

Set input gain of reflected signal. Default is 0.6.

out_gain

Set output gain of reflected signal. Default is 0.3.

delays

Set list of time intervals in milliseconds between original signal and reflections separated by ’|’. Allowed range for each delay is (0 - 90000.0]. Default is 1000.

decays

Set list of loudnesses of reflected signals separated by ’|’. Allowed range for each decay is (0 - 1.0]. Default is 0.5.

6.4.1 Examples

  • Make it sound as if there are twice as many instruments as are actually playing:
    aecho=0.8:0.88:60:0.4
    
  • If delay is very short, then it sound like a (metallic) robot playing music:
    aecho=0.8:0.88:6:0.4
    
  • A longer delay will sound like an open air concert in the mountains:
    aecho=0.8:0.9:1000:0.3
    
  • Same as above but with one more mountain:
    aecho=0.8:0.9:1000|1800:0.3|0.25
    

6.5 aemphasis

Audio emphasis filter creates or restores material directly taken from LPs or emphased CDs with different filter curves. E.g. to store music on vinyl the signal has to be altered by a filter first to even out the disadvantages of this recording medium. Once the material is played back the inverse filter has to be applied to restore the distortion of the frequency response.

The filter accepts the following options:

level_in

Set input gain.

level_out

Set output gain.

mode

Set filter mode. For restoring material use reproduction mode, otherwise use production mode. Default is reproduction mode.

type

Set filter type. Selects medium. Can be one of the following:

col

select Columbia.

emi

select EMI.

bsi

select BSI (78RPM).

riaa

select RIAA.

cd

select Compact Disc (CD).

50fm

select 50µs (FM).

75fm

select 75µs (FM).

50kf

select 50µs (FM-KF).

75kf

select 75µs (FM-KF).

6.6 aeval

Modify an audio signal according to the specified expressions.

This filter accepts one or more expressions (one for each channel), which are evaluated and used to modify a corresponding audio signal.

It accepts the following parameters:

exprs

Set the ’|’-separated expressions list for each separate channel. If the number of input channels is greater than the number of expressions, the last specified expression is used for the remaining output channels.

channel_layout, c

Set output channel layout. If not specified, the channel layout is specified by the number of expressions. If set to ‘same’, it will use by default the same input channel layout.

Each expression in exprs can contain the following constants and functions:

ch

channel number of the current expression

n

number of the evaluated sample, starting from 0

s

sample rate

t

time of the evaluated sample expressed in seconds

nb_in_channels
nb_out_channels

input and output number of channels

val(CH)

the value of input channel with number CH

Note: this filter is slow. For faster processing you should use a dedicated filter.

6.6.1 Examples

  • Half volume:
    aeval=val(ch)/2:c=same
    
  • Invert phase of the second channel:
    aeval=val(0)|-val(1)
    

6.7 afade

Apply fade-in/out effect to input audio.

A description of the accepted parameters follows.

type, t

Specify the effect type, can be either in for fade-in, or out for a fade-out effect. Default is in.

start_sample, ss

Specify the number of the start sample for starting to apply the fade effect. Default is 0.

nb_samples, ns

Specify the number of samples for which the fade effect has to last. At the end of the fade-in effect the output audio will have the same volume as the input audio, at the end of the fade-out transition the output audio will be silence. Default is 44100.

start_time, st

Specify the start time of the fade effect. Default is 0. The value must be specified as a time duration; see (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax. If set this option is used instead of start_sample.

duration, d

Specify the duration of the fade effect. See (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax. At the end of the fade-in effect the output audio will have the same volume as the input audio, at the end of the fade-out transition the output audio will be silence. By default the duration is determined by nb_samples. If set this option is used instead of nb_samples.

curve

Set curve for fade transition.

It accepts the following values:

tri

select triangular, linear slope (default)

qsin

select quarter of sine wave

hsin

select half of sine wave

esin

select exponential sine wave

log

select logarithmic

ipar

select inverted parabola

qua

select quadratic

cub

select cubic

squ

select square root

cbr

select cubic root

par

select parabola

exp

select exponential

iqsin

select inverted quarter of sine wave

ihsin

select inverted half of sine wave

dese

select double-exponential seat

desi

select double-exponential sigmoid

6.7.1 Examples

  • Fade in first 15 seconds of audio:
    afade=t=in:ss=0:d=15
    
  • Fade out last 25 seconds of a 900 seconds audio:
    afade=t=out:st=875:d=25
    

6.8 afftfilt

Apply arbitrary expressions to samples in frequency domain.

real

Set frequency domain real expression for each separate channel separated by ’|’. Default is "1". If the number of input channels is greater than the number of expressions, the last specified expression is used for the remaining output channels.

imag

Set frequency domain imaginary expression for each separate channel separated by ’|’. If not set, real option is used.

Each expression in real and imag can contain the following constants:

sr

sample rate

b

current frequency bin number

nb

number of available bins

ch

channel number of the current expression

chs

number of channels

pts

current frame pts

win_size

Set window size.

It accepts the following values:

w16
w32
w64
w128
w256
w512
w1024
w2048
w4096
w8192
w16384
w32768
w65536

Default is w4096

win_func

Set window function. Default is hann.

overlap

Set window overlap. If set to 1, the recommended overlap for selected window function will be picked. Default is 0.75.

6.8.1 Examples

  • Leave almost only low frequencies in audio:
    afftfilt="1-clip((b/nb)*b,0,1)"
    

6.9 aformat

Set output format constraints for the input audio. The framework will negotiate the most appropriate format to minimize conversions.

It accepts the following parameters:

sample_fmts

A ’|’-separated list of requested sample formats.

sample_rates

A ’|’-separated list of requested sample rates.

channel_layouts

A ’|’-separated list of requested channel layouts.

See (ffmpeg-utils)the Channel Layout section in the ffmpeg-utils(1) manual for the required syntax.

If a parameter is omitted, all values are allowed.

Force the output to either unsigned 8-bit or signed 16-bit stereo

aformat=sample_fmts=u8|s16:channel_layouts=stereo

6.10 agate

A gate is mainly used to reduce lower parts of a signal. This kind of signal processing reduces disturbing noise between useful signals.

Gating is done by detecting the volume below a chosen level threshold and divide it by the factor set with ratio. The bottom of the noise floor is set via range. Because an exact manipulation of the signal would cause distortion of the waveform the reduction can be levelled over time. This is done by setting attack and release.

attack determines how long the signal has to fall below the threshold before any reduction will occur and release sets the time the signal has to raise above the threshold to reduce the reduction again. Shorter signals than the chosen attack time will be left untouched.

level_in

Set input level before filtering. Default is 1. Allowed range is from 0.015625 to 64.

range

Set the level of gain reduction when the signal is below the threshold. Default is 0.06125. Allowed range is from 0 to 1.

threshold

If a signal rises above this level the gain reduction is released. Default is 0.125. Allowed range is from 0 to 1.

ratio

Set a ratio about which the signal is reduced. Default is 2. Allowed range is from 1 to 9000.

attack

Amount of milliseconds the signal has to rise above the threshold before gain reduction stops. Default is 20 milliseconds. Allowed range is from 0.01 to 9000.

release

Amount of milliseconds the signal has to fall below the threshold before the reduction is increased again. Default is 250 milliseconds. Allowed range is from 0.01 to 9000.

makeup

Set amount of amplification of signal after processing. Default is 1. Allowed range is from 1 to 64.

knee

Curve the sharp knee around the threshold to enter gain reduction more softly. Default is 2.828427125. Allowed range is from 1 to 8.

detection

Choose if exact signal should be taken for detection or an RMS like one. Default is rms. Can be peak or rms.

link

Choose if the average level between all channels or the louder channel affects the reduction. Default is average. Can be average or maximum.

6.11 alimiter

The limiter prevents input signal from raising over a desired threshold. This limiter uses lookahead technology to prevent your signal from distorting. It means that there is a small delay after signal is processed. Keep in mind that the delay it produces is the attack time you set.

The filter accepts the following options:

level_in

Set input gain. Default is 1.

level_out

Set output gain. Default is 1.

limit

Don’t let signals above this level pass the limiter. Default is 1.

attack

The limiter will reach its attenuation level in this amount of time in milliseconds. Default is 5 milliseconds.

release

Come back from limiting to attenuation 1.0 in this amount of milliseconds. Default is 50 milliseconds.

asc

When gain reduction is always needed ASC takes care of releasing to an average reduction level rather than reaching a reduction of 0 in the release time.

asc_level

Select how much the release time is affected by ASC, 0 means nearly no changes in release time while 1 produces higher release times.

level

Auto level output signal. Default is enabled. This normalizes audio back to 0dB if enabled.

Depending on picked setting it is recommended to upsample input 2x or 4x times with aresample before applying this filter.

6.12 allpass

Apply a two-pole all-pass filter with central frequency (in Hz) frequency, and filter-width width. An all-pass filter changes the audio’s frequency to phase relationship without changing its frequency to amplitude relationship.

The filter accepts the following options:

frequency, f

Set frequency in Hz.

width_type

Set method to specify band-width of filter.

h

Hz

q

Q-Factor

o

octave

s

slope

width, w

Specify the band-width of a filter in width_type units.

6.13 amerge

Merge two or more audio streams into a single multi-channel stream.

The filter accepts the following options:

inputs

Set the number of inputs. Default is 2.

If the channel layouts of the inputs are disjoint, and therefore compatible, the channel layout of the output will be set accordingly and the channels will be reordered as necessary. If the channel layouts of the inputs are not disjoint, the output will have all the channels of the first input then all the channels of the second input, in that order, and the channel layout of the output will be the default value corresponding to the total number of channels.

For example, if the first input is in 2.1 (FL+FR+LF) and the second input is FC+BL+BR, then the output will be in 5.1, with the channels in the following order: a1, a2, b1, a3, b2, b3 (a1 is the first channel of the first input, b1 is the first channel of the second input).

On the other hand, if both input are in stereo, the output channels will be in the default order: a1, a2, b1, b2, and the channel layout will be arbitrarily set to 4.0, which may or may not be the expected value.

All inputs must have the same sample rate, and format.

If inputs do not have the same duration, the output will stop with the shortest.

6.13.1 Examples

  • Merge two mono files into a stereo stream:
    amovie=left.wav [l] ; amovie=right.mp3 [r] ; [l] [r] amerge
    
  • Multiple merges assuming 1 video stream and 6 audio streams in input.mkv:
    ffmpeg -i input.mkv -filter_complex "[0:1][0:2][0:3][0:4][0:5][0:6] amerge=inputs=6" -c:a pcm_s16le output.mkv
    

6.14 amix

Mixes multiple audio inputs into a single output.

Note that this filter only supports float samples (the amerge and pan audio filters support many formats). If the amix input has integer samples then aresample will be automatically inserted to perform the conversion to float samples.

For example

ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT

will mix 3 input audio streams to a single output with the same duration as the first input and a dropout transition time of 3 seconds.

It accepts the following parameters:

inputs

The number of inputs. If unspecified, it defaults to 2.

duration

How to determine the end-of-stream.

longest

The duration of the longest input. (default)

shortest

The duration of the shortest input.

first

The duration of the first input.

dropout_transition

The transition time, in seconds, for volume renormalization when an input stream ends. The default value is 2 seconds.

6.15 anequalizer

High-order parametric multiband equalizer for each channel.

It accepts the following parameters:

params

This option string is in format: "cchn f=cf w=w g=g t=f | ..." Each equalizer band is separated by ’|’.

chn

Set channel number to which equalization will be applied. If input doesn’t have that channel the entry is ignored.

cf

Set central frequency for band. If input doesn’t have that frequency the entry is ignored.

w

Set band width in hertz.

g

Set band gain in dB.

f

Set filter type for band, optional, can be:

0

Butterworth, this is default.

1

Chebyshev type 1.

2

Chebyshev type 2.

curves

With this option activated frequency response of anequalizer is displayed in video stream.

size

Set video stream size. Only useful if curves option is activated.

mgain

Set max gain that will be displayed. Only useful if curves option is activated. Setting this to reasonable value allows to display gain which is derived from neighbour bands which are too close to each other and thus produce higher gain when both are activated.

fscale

Set frequency scale used to draw frequency response in video output. Can be linear or logarithmic. Default is logarithmic.

colors

Set color for each channel curve which is going to be displayed in video stream. This is list of color names separated by space or by ’|’. Unrecognised or missing colors will be replaced by white color.

6.15.1 Examples

  • Lower gain by 10 of central frequency 200Hz and width 100 Hz for first 2 channels using Chebyshev type 1 filter:
    anequalizer=c0 f=200 w=100 g=-10 t=1|c1 f=200 w=100 g=-10 t=1
    

6.15.2 Commands

This filter supports the following commands:

change

Alter existing filter parameters. Syntax for the commands is : "fN|f=freq|w=width|g=gain"

fN is existing filter number, starting from 0, if no such filter is available error is returned. freq set new frequency parameter. width set new width parameter in herz. gain set new gain parameter in dB.

Full filter invocation with asendcmd may look like this: asendcmd=c=’4.0 anequalizer change 0|f=200|w=50|g=1’,anequalizer=...

6.16 anull

Pass the audio source unchanged to the output.

6.17 apad

Pad the end of an audio stream with silence.

This can be used together with ffmpeg -shortest to extend audio streams to the same length as the video stream.

A description of the accepted options follows.

packet_size

Set silence packet size. Default value is 4096.

pad_len

Set the number of samples of silence to add to the end. After the value is reached, the stream is terminated. This option is mutually exclusive with whole_len.

whole_len

Set the minimum total number of samples in the output audio stream. If the value is longer than the input audio length, silence is added to the end, until the value is reached. This option is mutually exclusive with pad_len.

If neither the pad_len nor the whole_len option is set, the filter will add silence to the end of the input stream indefinitely.

6.17.1 Examples

  • Add 1024 samples of silence to the end of the input:
    apad=pad_len=1024
    
  • Make sure the audio output will contain at least 10000 samples, pad the input with silence if required:
    apad=whole_len=10000
    
  • Use ffmpeg to pad the audio input with silence, so that the video stream will always result the shortest and will be converted until the end in the output file when using the shortest option:
    ffmpeg -i VIDEO -i AUDIO -filter_complex "[1:0]apad" -shortest OUTPUT
    

6.18 aphaser

Add a phasing effect to the input audio.

A phaser filter creates series of peaks and troughs in the frequency spectrum. The position of the peaks and troughs are modulated so that they vary over time, creating a sweeping effect.

A description of the accepted parameters follows.

in_gain

Set input gain. Default is 0.4.

out_gain

Set output gain. Default is 0.74

delay

Set delay in milliseconds. Default is 3.0.

decay

Set decay. Default is 0.4.

speed

Set modulation speed in Hz. Default is 0.5.

type

Set modulation type. Default is triangular.

It accepts the following values:

triangular, t
sinusoidal, s

6.19 apulsator

Audio pulsator is something between an autopanner and a tremolo. But it can produce funny stereo effects as well. Pulsator changes the volume of the left and right channel based on a LFO (low frequency oscillator) with different waveforms and shifted phases. This filter have the ability to define an offset between left and right channel. An offset of 0 means that both LFO shapes match each other. The left and right channel are altered equally - a conventional tremolo. An offset of 50% means that the shape of the right channel is exactly shifted in phase (or moved backwards about half of the frequency) - pulsator acts as an autopanner. At 1 both curves match again. Every setting in between moves the phase shift gapless between all stages and produces some "bypassing" sounds with sine and triangle waveforms. The more you set the offset near 1 (starting from the 0.5) the faster the signal passes from the left to the right speaker.

The filter accepts the following options:

level_in

Set input gain. By default it is 1. Range is [0.015625 - 64].

level_out

Set output gain. By default it is 1. Range is [0.015625 - 64].

mode

Set waveform shape the LFO will use. Can be one of: sine, triangle, square, sawup or sawdown. Default is sine.

amount

Set modulation. Define how much of original signal is affected by the LFO.

offset_l

Set left channel offset. Default is 0. Allowed range is [0 - 1].

offset_r

Set right channel offset. Default is 0.5. Allowed range is [0 - 1].

width

Set pulse width. Default is 1. Allowed range is [0 - 2].

timing

Set possible timing mode. Can be one of: bpm, ms or hz. Default is hz.

bpm

Set bpm. Default is 120. Allowed range is [30 - 300]. Only used if timing is set to bpm.

ms

Set ms. Default is 500. Allowed range is [10 - 2000]. Only used if timing is set to ms.

hz

Set frequency in Hz. Default is 2. Allowed range is [0.01 - 100]. Only used if timing is set to hz.

6.20 aresample

Resample the input audio to the specified parameters, using the libswresample library. If none are specified then the filter will automatically convert between its input and output.

This filter is also able to stretch/squeeze the audio data to make it match the timestamps or to inject silence / cut out audio to make it match the timestamps, do a combination of both or do neither.

The filter accepts the syntax [sample_rate:]resampler_options, where sample_rate expresses a sample rate and resampler_options is a list of key=value pairs, separated by ":". See the ffmpeg-resampler manual for the complete list of supported options.

6.20.1 Examples

  • Resample the input audio to 44100Hz:
    aresample=44100
    
  • Stretch/squeeze samples to the given timestamps, with a maximum of 1000 samples per second compensation:
    aresample=async=1000
    

6.21 asetnsamples

Set the number of samples per each output audio frame.

The last output packet may contain a different number of samples, as the filter will flush all the remaining samples when the input audio signal its end.

The filter accepts the following options:

nb_out_samples, n

Set the number of frames per each output audio frame. The number is intended as the number of samples per each channel. Default value is 1024.

pad, p

If set to 1, the filter will pad the last audio frame with zeroes, so that the last frame will contain the same number of samples as the previous ones. Default value is 1.

For example, to set the number of per-frame samples to 1234 and disable padding for the last frame, use:

asetnsamples=n=1234:p=0

6.22 asetrate

Set the sample rate without altering the PCM data. This will result in a change of speed and pitch.

The filter accepts the following options:

sample_rate, r

Set the output sample rate. Default is 44100 Hz.

6.23 ashowinfo

Show a line containing various information for each input audio frame. The input audio is not modified.

The shown line contains a sequence of key/value pairs of the form key:value.

The following values are shown in the output:

n

The (sequential) number of the input frame, starting from 0.

pts

The presentation timestamp of the input frame, in time base units; the time base depends on the filter input pad, and is usually 1/sample_rate.

pts_time

The presentation timestamp of the input frame in seconds.

pos

position of the frame in the input stream, -1 if this information in unavailable and/or meaningless (for example in case of synthetic audio)

fmt

The sample format.

chlayout

The channel layout.

rate

The sample rate for the audio frame.

nb_samples

The number of samples (per channel) in the frame.

checksum

The Adler-32 checksum (printed in hexadecimal) of the audio data. For planar audio, the data is treated as if all the planes were concatenated.

plane_checksums

A list of Adler-32 checksums for each data plane.

6.24 astats

Display time domain statistical information about the audio channels. Statistics are calculated and displayed for each audio channel and, where applicable, an overall figure is also given.

It accepts the following option:

length

Short window length in seconds, used for peak and trough RMS measurement. Default is 0.05 (50 milliseconds). Allowed range is [0.1 - 10].

metadata

Set metadata injection. All the metadata keys are prefixed with lavfi.astats.X, where X is channel number starting from 1 or string Overall. Default is disabled.

Available keys for each channel are: DC_offset Min_level Max_level Min_difference Max_difference Mean_difference Peak_level RMS_peak RMS_trough Crest_factor Flat_factor Peak_count Bit_depth

and for Overall: DC_offset Min_level Max_level Min_difference Max_difference Mean_difference Peak_level RMS_level RMS_peak RMS_trough Flat_factor Peak_count Bit_depth Number_of_samples

For example full key look like this lavfi.astats.1.DC_offset or this lavfi.astats.Overall.Peak_count.

For description what each key means read below.

reset

Set number of frame after which stats are going to be recalculated. Default is disabled.

A description of each shown parameter follows:

DC offset

Mean amplitude displacement from zero.

Min level

Minimal sample level.

Max level

Maximal sample level.

Min difference

Minimal difference between two consecutive samples.

Max difference

Maximal difference between two consecutive samples.

Mean difference

Mean difference between two consecutive samples. The average of each difference between two consecutive samples.

Peak level dB
RMS level dB

Standard peak and RMS level measured in dBFS.

RMS peak dB
RMS trough dB

Peak and trough values for RMS level measured over a short window.

Crest factor

Standard ratio of peak to RMS level (note: not in dB).

Flat factor

Flatness (i.e. consecutive samples with the same value) of the signal at its peak levels (i.e. either Min level or Max level).

Peak count

Number of occasions (not the number of samples) that the signal attained either Min level or Max level.

Bit depth

Overall bit depth of audio. Number of bits used for each sample.

6.25 asyncts

Synchronize audio data with timestamps by squeezing/stretching it and/or dropping samples/adding silence when needed.

This filter is not built by default, please use aresample to do squeezing/stretching.

It accepts the following parameters:

compensate

Enable stretching/squeezing the data to make it match the timestamps. Disabled by default. When disabled, time gaps are covered with silence.

min_delta

The minimum difference between timestamps and audio data (in seconds) to trigger adding/dropping samples. The default value is 0.1. If you get an imperfect sync with this filter, try setting this parameter to 0.

max_comp

The maximum compensation in samples per second. Only relevant with compensate=1. The default value is 500.

first_pts

Assume that the first PTS should be this value. The time base is 1 / sample rate. This allows for padding/trimming at the start of the stream. By default, no assumption is made about the first frame’s expected PTS, so no padding or trimming is done. For example, this could be set to 0 to pad the beginning with silence if an audio stream starts after the video stream or to trim any samples with a negative PTS due to encoder delay.

6.26 atempo

Adjust audio tempo.

The filter accepts exactly one parameter, the audio tempo. If not specified then the filter will assume nominal 1.0 tempo. Tempo must be in the [0.5, 2.0] range.

6.26.1 Examples

  • Slow down audio to 80% tempo:
    atempo=0.8
    
  • To speed up audio to 125% tempo:
    atempo=1.25
    

6.27 atrim

Trim the input so that the output contains one continuous subpart of the input.

It accepts the following parameters:

start

Timestamp (in seconds) of the start of the section to keep. I.e. the audio sample with the timestamp start will be the first sample in the output.

end

Specify time of the first audio sample that will be dropped, i.e. the audio sample immediately preceding the one with the timestamp end will be the last sample in the output.

start_pts

Same as start, except this option sets the start timestamp in samples instead of seconds.

end_pts

Same as end, except this option sets the end timestamp in samples instead of seconds.

duration

The maximum duration of the output in seconds.

start_sample

The number of the first sample that should be output.

end_sample

The number of the first sample that should be dropped.

start, end, and duration are expressed as time duration specifications; see (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual.

Note that the first two sets of the start/end options and the duration option look at the frame timestamp, while the _sample options simply count the samples that pass through the filter. So start/end_pts and start/end_sample will give different results when the timestamps are wrong, inexact or do not start at zero. Also note that this filter does not modify the timestamps. If you wish to have the output timestamps start at zero, insert the asetpts filter after the atrim filter.

If multiple start or end options are set, this filter tries to be greedy and keep all samples that match at least one of the specified constraints. To keep only the part that matches all the constraints at once, chain multiple atrim filters.

The defaults are such that all the input is kept. So it is possible to set e.g. just the end values to keep everything before the specified time.

Examples:

  • Drop everything except the second minute of input:
    ffmpeg -i INPUT -af atrim=60:120
    
  • Keep only the first 1000 samples:
    ffmpeg -i INPUT -af atrim=end_sample=1000
    

6.28 bandpass

Apply a two-pole Butterworth band-pass filter with central frequency frequency, and (3dB-point) band-width width. The csg option selects a constant skirt gain (peak gain = Q) instead of the default: constant 0dB peak gain. The filter roll off at 6dB per octave (20dB per decade).

The filter accepts the following options:

frequency, f

Set the filter’s central frequency. Default is 3000.

csg

Constant skirt gain if set to 1. Defaults to 0.

width_type

Set method to specify band-width of filter.

h

Hz

q

Q-Factor

o

octave

s

slope

width, w

Specify the band-width of a filter in width_type units.

6.29 bandreject

Apply a two-pole Butterworth band-reject filter with central frequency frequency, and (3dB-point) band-width width. The filter roll off at 6dB per octave (20dB per decade).

The filter accepts the following options:

frequency, f

Set the filter’s central frequency. Default is 3000.

width_type

Set method to specify band-width of filter.

h

Hz

q

Q-Factor

o

octave

s

slope

width, w

Specify the band-width of a filter in width_type units.

6.30 bass

Boost or cut the bass (lower) frequencies of the audio using a two-pole shelving filter with a response similar to that of a standard hi-fi’s tone-controls. This is also known as shelving equalisation (EQ).

The filter accepts the following options:

gain, g

Give the gain at 0 Hz. Its useful range is about -20 (for a large cut) to +20 (for a large boost). Beware of clipping when using a positive gain.

frequency, f

Set the filter’s central frequency and so can be used to extend or reduce the frequency range to be boosted or cut. The default value is 100 Hz.

width_type

Set method to specify band-width of filter.

h

Hz

q

Q-Factor

o

octave

s

slope

width, w

Determine how steep is the filter’s shelf transition.

6.31 biquad

Apply a biquad IIR filter with the given coefficients. Where b0, b1, b2 and a0, a1, a2 are the numerator and denominator coefficients respectively.

6.32 bs2b

Bauer stereo to binaural transformation, which improves headphone listening of stereo audio records.

It accepts the following parameters:

profile

Pre-defined crossfeed level.

default

Default level (fcut=700, feed=50).

cmoy

Chu Moy circuit (fcut=700, feed=60).

jmeier

Jan Meier circuit (fcut=650, feed=95).

fcut

Cut frequency (in Hz).

feed

Feed level (in Hz).

6.33 channelmap

Remap input channels to new locations.

It accepts the following parameters:

channel_layout

The channel layout of the output stream.

map

Map channels from input to output. The argument is a ’|’-separated list of mappings, each in the in_channel-out_channel or in_channel form. in_channel can be either the name of the input channel (e.g. FL for front left) or its index in the input channel layout. out_channel is the name of the output channel or its index in the output channel layout. If out_channel is not given then it is implicitly an index, starting with zero and increasing by one for each mapping.

If no mapping is present, the filter will implicitly map input channels to output channels, preserving indices.

For example, assuming a 5.1+downmix input MOV file,

ffmpeg -i in.mov -filter 'channelmap=map=DL-FL|DR-FR' out.wav

will create an output WAV file tagged as stereo from the downmix channels of the input.

To fix a 5.1 WAV improperly encoded in AAC’s native channel order

ffmpeg -i in.wav -filter 'channelmap=1|2|0|5|3|4:5.1' out.wav

6.34 channelsplit

Split each channel from an input audio stream into a separate output stream.

It accepts the following parameters:

channel_layout

The channel layout of the input stream. The default is "stereo".

For example, assuming a stereo input MP3 file,

ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv

will create an output Matroska file with two audio streams, one containing only the left channel and the other the right channel.

Split a 5.1 WAV file into per-channel files:

ffmpeg -i in.wav -filter_complex
'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
-map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
side_right.wav

6.35 chorus

Add a chorus effect to the audio.

Can make a single vocal sound like a chorus, but can also be applied to instrumentation.

Chorus resembles an echo effect with a short delay, but whereas with echo the delay is constant, with chorus, it is varied using using sinusoidal or triangular modulation. The modulation depth defines the range the modulated delay is played before or after the delay. Hence the delayed sound will sound slower or faster, that is the delayed sound tuned around the original one, like in a chorus where some vocals are slightly off key.

It accepts the following parameters:

in_gain

Set input gain. Default is 0.4.

out_gain

Set output gain. Default is 0.4.

delays

Set delays. A typical delay is around 40ms to 60ms.

decays

Set decays.

speeds

Set speeds.

depths

Set depths.

6.35.1 Examples

  • A single delay:
    chorus=0.7:0.9:55:0.4:0.25:2
    
  • Two delays:
    chorus=0.6:0.9:50|60:0.4|0.32:0.25|0.4:2|1.3
    
  • Fuller sounding chorus with three delays:
    chorus=0.5:0.9:50|60|40:0.4|0.32|0.3:0.25|0.4|0.3:2|2.3|1.3
    

6.36 compand

Compress or expand the audio’s dynamic range.

It accepts the following parameters:

attacks
decays

A list of times in seconds for each channel over which the instantaneous level of the input signal is averaged to determine its volume. attacks refers to increase of volume and decays refers to decrease of volume. For most situations, the attack time (response to the audio getting louder) should be shorter than the decay time, because the human ear is more sensitive to sudden loud audio than sudden soft audio. A typical value for attack is 0.3 seconds and a typical value for decay is 0.8 seconds. If specified number of attacks & decays is lower than number of channels, the last set attack/decay will be used for all remaining channels.

points

A list of points for the transfer function, specified in dB relative to the maximum possible signal amplitude. Each key points list must be defined using the following syntax: x0/y0|x1/y1|x2/y2|.... or x0/y0 x1/y1 x2/y2 ....

The input values must be in strictly increasing order but the transfer function does not have to be monotonically rising. The point 0/0 is assumed but may be overridden (by 0/out-dBn). Typical values for the transfer function are -70/-70|-60/-20.

soft-knee

Set the curve radius in dB for all joints. It defaults to 0.01.

gain

Set the additional gain in dB to be applied at all points on the transfer function. This allows for easy adjustment of the overall gain. It defaults to 0.

volume

Set an initial volume, in dB, to be assumed for each channel when filtering starts. This permits the user to supply a nominal level initially, so that, for example, a very large gain is not applied to initial signal levels before the companding has begun to operate. A typical value for audio which is initially quiet is -90 dB. It defaults to 0.

delay

Set a delay, in seconds. The input audio is analyzed immediately, but audio is delayed before being fed to the volume adjuster. Specifying a delay approximately equal to the attack/decay times allows the filter to effectively operate in predictive rather than reactive mode. It defaults to 0.

6.36.1 Examples

  • Make music with both quiet and loud passages suitable for listening to in a noisy environment:
    compand=.3|.3:1|1:-90/-60|-60/-40|-40/-30|-20/-20:6:0:-90:0.2
    

    Another example for audio with whisper and explosion parts:

    compand=0|0:1|1:-90/-900|-70/-70|-30/-9|0/-3:6:0:0:0
    
  • A noise gate for when the noise is at a lower level than the signal:
    compand=.1|.1:.2|.2:-900/-900|-50.1/-900|-50/-50:.01:0:-90:.1
    
  • Here is another noise gate, this time for when the noise is at a higher level than the signal (making it, in some ways, similar to squelch):
    compand=.1|.1:.1|.1:-45.1/-45.1|-45/-900|0/-900:.01:45:-90:.1
    
  • 2:1 compression starting at -6dB:
    compand=points=-80/-80|-6/-6|0/-3.8|20/3.5
    
  • 2:1 compression starting at -9dB:
    compand=points=-80/-80|-9/-9|0/-5.3|20/2.9
    
  • 2:1 compression starting at -12dB:
    compand=points=-80/-80|-12/-12|0/-6.8|20/1.9
    
  • 2:1 compression starting at -18dB:
    compand=points=-80/-80|-18/-18|0/-9.8|20/0.7
    
  • 3:1 compression starting at -15dB:
    compand=points=-80/-80|-15/-15|0/-10.8|20/-5.2
    
  • Compressor/Gate:
    compand=points=-80/-105|-62/-80|-15.4/-15.4|0/-12|20/-7.6
    
  • Expander:
    compand=attacks=0:points=-80/-169|-54/-80|-49.5/-64.6|-41.1/-41.1|-25.8/-15|-10.8/-4.5|0/0|20/8.3
    
  • Hard limiter at -6dB:
    compand=attacks=0:points=-80/-80|-6/-6|20/-6
    
  • Hard limiter at -12dB:
    compand=attacks=0:points=-80/-80|-12/-12|20/-12
    
  • Hard noise gate at -35 dB:
    compand=attacks=0:points=-80/-115|-35.1/-80|-35/-35|20/20
    
  • Soft limiter:
    compand=attacks=0:points=-80/-80|-12.4/-12.4|-6/-8|0/-6.8|20/-2.8
    

6.37 compensationdelay

Compensation Delay Line is a metric based delay to compensate differing positions of microphones or speakers.

For example, you have recorded guitar with two microphones placed in different location. Because the front of sound wave has fixed speed in normal conditions, the phasing of microphones can vary and depends on their location and interposition. The best sound mix can be achieved when these microphones are in phase (synchronized). Note that distance of ~30 cm between microphones makes one microphone to capture signal in antiphase to another microphone. That makes the final mix sounding moody. This filter helps to solve phasing problems by adding different delays to each microphone track and make them synchronized.

The best result can be reached when you take one track as base and synchronize other tracks one by one with it. Remember that synchronization/delay tolerance depends on sample rate, too. Higher sample rates will give more tolerance.

It accepts the following parameters:

mm

Set millimeters distance. This is compensation distance for fine tuning. Default is 0.

cm

Set cm distance. This is compensation distance for tightening distance setup. Default is 0.

m

Set meters distance. This is compensation distance for hard distance setup. Default is 0.

dry

Set dry amount. Amount of unprocessed (dry) signal. Default is 0.

wet

Set wet amount. Amount of processed (wet) signal. Default is 1.

temp

Set temperature degree in Celsius. This is the temperature of the environment. Default is 20.

6.38 dcshift

Apply a DC shift to the audio.

This can be useful to remove a DC offset (caused perhaps by a hardware problem in the recording chain) from the audio. The effect of a DC offset is reduced headroom and hence volume. The astats filter can be used to determine if a signal has a DC offset.

shift

Set the DC shift, allowed range is [-1, 1]. It indicates the amount to shift the audio.

limitergain

Optional. It should have a value much less than 1 (e.g. 0.05 or 0.02) and is used to prevent clipping.

6.39 dynaudnorm

Dynamic Audio Normalizer.

This filter applies a certain amount of gain to the input audio in order to bring its peak magnitude to a target level (e.g. 0 dBFS). However, in contrast to more "simple" normalization algorithms, the Dynamic Audio Normalizer *dynamically* re-adjusts the gain factor to the input audio. This allows for applying extra gain to the "quiet" sections of the audio while avoiding distortions or clipping the "loud" sections. In other words: The Dynamic Audio Normalizer will "even out" the volume of quiet and loud sections, in the sense that the volume of each section is brought to the same target level. Note, however, that the Dynamic Audio Normalizer achieves this goal *without* applying "dynamic range compressing". It will retain 100% of the dynamic range *within* each section of the audio file.

f

Set the frame length in milliseconds. In range from 10 to 8000 milliseconds. Default is 500 milliseconds. The Dynamic Audio Normalizer processes the input audio in small chunks, referred to as frames. This is required, because a peak magnitude has no meaning for just a single sample value. Instead, we need to determine the peak magnitude for a contiguous sequence of sample values. While a "standard" normalizer would simply use the peak magnitude of the complete file, the Dynamic Audio Normalizer determines the peak magnitude individually for each frame. The length of a frame is specified in milliseconds. By default, the Dynamic Audio Normalizer uses a frame length of 500 milliseconds, which has been found to give good results with most files. Note that the exact frame length, in number of samples, will be determined automatically, based on the sampling rate of the individual input audio file.

g

Set the Gaussian filter window size. In range from 3 to 301, must be odd number. Default is 31. Probably the most important parameter of the Dynamic Audio Normalizer is the window size of the Gaussian smoothing filter. The filter’s window size is specified in frames, centered around the current frame. For the sake of simplicity, this must be an odd number. Consequently, the default value of 31 takes into account the current frame, as well as the 15 preceding frames and the 15 subsequent frames. Using a larger window results in a stronger smoothing effect and thus in less gain variation, i.e. slower gain adaptation. Conversely, using a smaller window results in a weaker smoothing effect and thus in more gain variation, i.e. faster gain adaptation. In other words, the more you increase this value, the more the Dynamic Audio Normalizer will behave like a "traditional" normalization filter. On the contrary, the more you decrease this value, the more the Dynamic Audio Normalizer will behave like a dynamic range compressor.

p

Set the target peak value. This specifies the highest permissible magnitude level for the normalized audio input. This filter will try to approach the target peak magnitude as closely as possible, but at the same time it also makes sure that the normalized signal will never exceed the peak magnitude. A frame’s maximum local gain factor is imposed directly by the target peak magnitude. The default value is 0.95 and thus leaves a headroom of 5%*. It is not recommended to go above this value.

m

Set the maximum gain factor. In range from 1.0 to 100.0. Default is 10.0. The Dynamic Audio Normalizer determines the maximum possible (local) gain factor for each input frame, i.e. the maximum gain factor that does not result in clipping or distortion. The maximum gain factor is determined by the frame’s highest magnitude sample. However, the Dynamic Audio Normalizer additionally bounds the frame’s maximum gain factor by a predetermined (global) maximum gain factor. This is done in order to avoid excessive gain factors in "silent" or almost silent frames. By default, the maximum gain factor is 10.0, For most inputs the default value should be sufficient and it usually is not recommended to increase this value. Though, for input with an extremely low overall volume level, it may be necessary to allow even higher gain factors. Note, however, that the Dynamic Audio Normalizer does not simply apply a "hard" threshold (i.e. cut off values above the threshold). Instead, a "sigmoid" threshold function will be applied. This way, the gain factors will smoothly approach the threshold value, but never exceed that value.

r

Set the target RMS. In range from 0.0 to 1.0. Default is 0.0 - disabled. By default, the Dynamic Audio Normalizer performs "peak" normalization. This means that the maximum local gain factor for each frame is defined (only) by the frame’s highest magnitude sample. This way, the samples can be amplified as much as possible without exceeding the maximum signal level, i.e. without clipping. Optionally, however, the Dynamic Audio Normalizer can also take into account the frame’s root mean square, abbreviated RMS. In electrical engineering, the RMS is commonly used to determine the power of a time-varying signal. It is therefore considered that the RMS is a better approximation of the "perceived loudness" than just looking at the signal’s peak magnitude. Consequently, by adjusting all frames to a constant RMS value, a uniform "perceived loudness" can be established. If a target RMS value has been specified, a frame’s local gain factor is defined as the factor that would result in exactly that RMS value. Note, however, that the maximum local gain factor is still restricted by the frame’s highest magnitude sample, in order to prevent clipping.

n

Enable channels coupling. By default is enabled. By default, the Dynamic Audio Normalizer will amplify all channels by the same amount. This means the same gain factor will be applied to all channels, i.e. the maximum possible gain factor is determined by the "loudest" channel. However, in some recordings, it may happen that the volume of the different channels is uneven, e.g. one channel may be "quieter" than the other one(s). In this case, this option can be used to disable the channel coupling. This way, the gain factor will be determined independently for each channel, depending only on the individual channel’s highest magnitude sample. This allows for harmonizing the volume of the different channels.

c

Enable DC bias correction. By default is disabled. An audio signal (in the time domain) is a sequence of sample values. In the Dynamic Audio Normalizer these sample values are represented in the -1.0 to 1.0 range, regardless of the original input format. Normally, the audio signal, or "waveform", should be centered around the zero point. That means if we calculate the mean value of all samples in a file, or in a single frame, then the result should be 0.0 or at least very close to that value. If, however, there is a significant deviation of the mean value from 0.0, in either positive or negative direction, this is referred to as a DC bias or DC offset. Since a DC bias is clearly undesirable, the Dynamic Audio Normalizer provides optional DC bias correction. With DC bias correction enabled, the Dynamic Audio Normalizer will determine the mean value, or "DC correction" offset, of each input frame and subtract that value from all of the frame’s sample values which ensures those samples are centered around 0.0 again. Also, in order to avoid "gaps" at the frame boundaries, the DC correction offset values will be interpolated smoothly between neighbouring frames.

b

Enable alternative boundary mode. By default is disabled. The Dynamic Audio Normalizer takes into account a certain neighbourhood around each frame. This includes the preceding frames as well as the subsequent frames. However, for the "boundary" frames, located at the very beginning and at the very end of the audio file, not all neighbouring frames are available. In particular, for the first few frames in the audio file, the preceding frames are not known. And, similarly, for the last few frames in the audio file, the subsequent frames are not known. Thus, the question arises which gain factors should be assumed for the missing frames in the "boundary" region. The Dynamic Audio Normalizer implements two modes to deal with this situation. The default boundary mode assumes a gain factor of exactly 1.0 for the missing frames, resulting in a smooth "fade in" and "fade out" at the beginning and at the end of the input, respectively.

s

Set the compress factor. In range from 0.0 to 30.0. Default is 0.0. By default, the Dynamic Audio Normalizer does not apply "traditional" compression. This means that signal peaks will not be pruned and thus the full dynamic range will be retained within each local neighbourhood. However, in some cases it may be desirable to combine the Dynamic Audio Normalizer’s normalization algorithm with a more "traditional" compression. For this purpose, the Dynamic Audio Normalizer provides an optional compression (thresholding) function. If (and only if) the compression feature is enabled, all input frames will be processed by a soft knee thresholding function prior to the actual normalization process. Put simply, the thresholding function is going to prune all samples whose magnitude exceeds a certain threshold value. However, the Dynamic Audio Normalizer does not simply apply a fixed threshold value. Instead, the threshold value will be adjusted for each individual frame. In general, smaller parameters result in stronger compression, and vice versa. Values below 3.0 are not recommended, because audible distortion may appear.

6.40 earwax

Make audio easier to listen to on headphones.

This filter adds ‘cues’ to 44.1kHz stereo (i.e. audio CD format) audio so that when listened to on headphones the stereo image is moved from inside your head (standard for headphones) to outside and in front of the listener (standard for speakers).

Ported from SoX.

6.41 equalizer

Apply a two-pole peaking equalisation (EQ) filter. With this filter, the signal-level at and around a selected frequency can be increased or decreased, whilst (unlike bandpass and bandreject filters) that at all other frequencies is unchanged.

In order to produce complex equalisation curves, this filter can be given several times, each with a different central frequency.

The filter accepts the following options:

frequency, f

Set the filter’s central frequency in Hz.

width_type

Set method to specify band-width of filter.

h

Hz

q

Q-Factor

o

octave

s

slope

width, w

Specify the band-width of a filter in width_type units.

gain, g

Set the required gain or attenuation in dB. Beware of clipping when using a positive gain.

6.41.1 Examples

  • Attenuate 10 dB at 1000 Hz, with a bandwidth of 200 Hz:
    equalizer=f=1000:width_type=h:width=200:g=-10
    
  • Apply 2 dB gain at 1000 Hz with Q 1 and attenuate 5 dB at 100 Hz with Q 2:
    equalizer=f=1000:width_type=q:width=1:g=2,equalizer=f=100:width_type=q:width=2:g=-5
    

6.42 extrastereo

Linearly increases the difference between left and right channels which adds some sort of "live" effect to playback.

The filter accepts the following option:

m

Sets the difference coefficient (default: 2.5). 0.0 means mono sound (average of both channels), with 1.0 sound will be unchanged, with -1.0 left and right channels will be swapped.

c

Enable clipping. By default is enabled.

6.43 firequalizer

Apply FIR Equalization using arbitrary frequency response.

The filter accepts the following option:

gain

Set gain curve equation (in dB). The expression can contain variables:

f

the evaluated frequency

sr

sample rate

ch

channel number, set to 0 when multichannels evaluation is disabled

chid

channel id, see libavutil/channel_layout.h, set to the first channel id when multichannels evaluation is disabled

chs

number of channels

chlayout

channel_layout, see libavutil/channel_layout.h

and functions:

gain_interpolate(f)

interpolate gain on frequency f based on gain_entry

This option is also available as command. Default is gain_interpolate(f).

gain_entry

Set gain entry for gain_interpolate function. The expression can contain functions:

entry(f, g)

store gain entry at frequency f with value g

This option is also available as command.

delay

Set filter delay in seconds. Higher value means more accurate. Default is 0.01.

accuracy

Set filter accuracy in Hz. Lower value means more accurate. Default is 5.

wfunc

Set window function. Acceptable values are:

rectangular

rectangular window, useful when gain curve is already smooth

hann

hann window (default)

hamming

hamming window

blackman

blackman window

nuttall3

3-terms continuous 1st derivative nuttall window

mnuttall3

minimum 3-terms discontinuous nuttall window

nuttall

4-terms continuous 1st derivative nuttall window

bnuttall

minimum 4-terms discontinuous nuttall (blackman-nuttall) window

bharris

blackman-harris window

fixed

If enabled, use fixed number of audio samples. This improves speed when filtering with large delay. Default is disabled.

multi

Enable multichannels evaluation on gain. Default is disabled.

zero_phase

Enable zero phase mode by substracting timestamp to compensate delay. Default is disabled.

6.43.1 Examples

  • lowpass at 1000 Hz:
    firequalizer=gain='if(lt(f,1000), 0, -INF)'
    
  • lowpass at 1000 Hz with gain_entry:
    firequalizer=gain_entry='entry(1000,0); entry(1001, -INF)'
    
  • custom equalization:
    firequalizer=gain_entry='entry(100,0); entry(400, -4); entry(1000, -6); entry(2000, 0)'
    
  • higher delay with zero phase to compensate delay:
    firequalizer=delay=0.1:fixed=on:zero_phase=on
    
  • lowpass on left channel, highpass on right channel:
    firequalizer=gain='if(eq(chid,1), gain_interpolate(f), if(eq(chid,2), gain_interpolate(1e6+f), 0))'
    :gain_entry='entry(1000, 0); entry(1001,-INF); entry(1e6+1000,0)':multi=on
    

6.44 flanger

Apply a flanging effect to the audio.

The filter accepts the following options:

delay

Set base delay in milliseconds. Range from 0 to 30. Default value is 0.

depth

Set added swep delay in milliseconds. Range from 0 to 10. Default value is 2.

regen

Set percentage regeneration (delayed signal feedback). Range from -95 to 95. Default value is 0.

width

Set percentage of delayed signal mixed with original. Range from 0 to 100. Default value is 71.

speed

Set sweeps per second (Hz). Range from 0.1 to 10. Default value is 0.5.

shape

Set swept wave shape, can be triangular or sinusoidal. Default value is sinusoidal.

phase

Set swept wave percentage-shift for multi channel. Range from 0 to 100. Default value is 25.

interp

Set delay-line interpolation, linear or quadratic. Default is linear.

6.45 highpass

Apply a high-pass filter with 3dB point frequency. The filter can be either single-pole, or double-pole (the default). The filter roll off at 6dB per pole per octave (20dB per pole per decade).

The filter accepts the following options:

frequency, f

Set frequency in Hz. Default is 3000.

poles, p

Set number of poles. Default is 2.

width_type

Set method to specify band-width of filter.

h

Hz

q

Q-Factor

o

octave

s

slope

width, w

Specify the band-width of a filter in width_type units. Applies only to double-pole filter. The default is 0.707q and gives a Butterworth response.

6.46 join

Join multiple input streams into one multi-channel stream.

It accepts the following parameters:

inputs

The number of input streams. It defaults to 2.

channel_layout

The desired output channel layout. It defaults to stereo.

map

Map channels from inputs to output. The argument is a ’|’-separated list of mappings, each in the input_idx.in_channel-out_channel form. input_idx is the 0-based index of the input stream. in_channel can be either the name of the input channel (e.g. FL for front left) or its index in the specified input stream. out_channel is the name of the output channel.

The filter will attempt to guess the mappings when they are not specified explicitly. It does so by first trying to find an unused matching input channel and if that fails it picks the first unused input channel.

Join 3 inputs (with properly set channel layouts):

ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT

Build a 5.1 output from 6 single-channel streams:

ffmpeg -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
'join=inputs=6:channel_layout=5.1:map=0.0-FL|1.0-FR|2.0-FC|3.0-SL|4.0-SR|5.0-LFE'
out

6.47 ladspa

Load a LADSPA (Linux Audio Developer’s Simple Plugin API) plugin.

To enable compilation of this filter you need to configure FFmpeg with --enable-ladspa.

file, f

Specifies the name of LADSPA plugin library to load. If the environment variable LADSPA_PATH is defined, the LADSPA plugin is searched in each one of the directories specified by the colon separated list in LADSPA_PATH, otherwise in the standard LADSPA paths, which are in this order: HOME/.ladspa/lib/, /usr/local/lib/ladspa/, /usr/lib/ladspa/.

plugin, p

Specifies the plugin within the library. Some libraries contain only one plugin, but others contain many of them. If this is not set filter will list all available plugins within the specified library.

controls, c

Set the ’|’ separated list of controls which are zero or more floating point values that determine the behavior of the loaded plugin (for example delay, threshold or gain). Controls need to be defined using the following syntax: c0=value0|c1=value1|c2=value2|..., where valuei is the value set on the i-th control. Alternatively they can be also defined using the following syntax: value0|value1|value2|..., where valuei is the value set on the i-th control. If controls is set to help, all available controls and their valid ranges are printed.

sample_rate, s

Specify the sample rate, default to 44100. Only used if plugin have zero inputs.

nb_samples, n

Set the number of samples per channel per each output frame, default is 1024. Only used if plugin have zero inputs.

duration, d

Set the minimum duration of the sourced audio. See (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax. Note that the resulting duration may be greater than the specified duration, as the generated audio is always cut at the end of a complete frame. If not specified, or the expressed duration is negative, the audio is supposed to be generated forever. Only used if plugin have zero inputs.

6.47.1 Examples

  • List all available plugins within amp (LADSPA example plugin) library:
    ladspa=file=amp
    
  • List all available controls and their valid ranges for vcf_notch plugin from VCF library:
    ladspa=f=vcf:p=vcf_notch:c=help
    
  • Simulate low quality audio equipment using Computer Music Toolkit (CMT) plugin library:
    ladspa=file=cmt:plugin=lofi:controls=c0=22|c1=12|c2=12
    
  • Add reverberation to the audio using TAP-plugins (Tom’s Audio Processing plugins):
    ladspa=file=tap_reverb:tap_reverb
    
  • Generate white noise, with 0.2 amplitude:
    ladspa=file=cmt:noise_source_white:c=c0=.2
    
  • Generate 20 bpm clicks using plugin C* Click - Metronome from the C* Audio Plugin Suite (CAPS) library:
    ladspa=file=caps:Click:c=c1=20'
    
  • Apply C* Eq10X2 - Stereo 10-band equaliser effect:
    ladspa=caps:Eq10X2:c=c0=-48|c9=-24|c3=12|c4=2
    
  • Increase volume by 20dB using fast lookahead limiter from Steve Harris SWH Plugins collection:
    ladspa=fast_lookahead_limiter_1913:fastLookaheadLimiter:20|0|2
    
  • Attenuate low frequencies using Multiband EQ from Steve Harris SWH Plugins collection:
    ladspa=mbeq_1197:mbeq:-24|-24|-24|0|0|0|0|0|0|0|0|0|0|0|0
    

6.47.2 Commands

This filter supports the following commands:

cN

Modify the N-th control value.

If the specified value is not valid, it is ignored and prior one is kept.

6.48 loudnorm

EBU R128 loudness normalization. Includes both dynamic and linear normalization modes. Support for both single pass (livestreams, files) and double pass (files) modes. This algorithm can target IL, LRA, and maximum true peak.

To enable compilation of this filter you need to configure FFmpeg with --enable-libebur128.

The filter accepts the following options:

I, i

Set integrated loudness target. Range is -70.0 - -5.0. Default value is -24.0.

LRA, lra

Set loudness range target. Range is 1.0 - 20.0. Default value is 7.0.

TP, tp

Set maximum true peak. Range is -9.0 - +0.0. Default value is -2.0.

measured_I, measured_i

Measured IL of input file. Range is -99.0 - +0.0.

measured_LRA, measured_lra

Measured LRA of input file. Range is 0.0 - 99.0.

measured_TP, measured_tp

Measured true peak of input file. Range is -99.0 - +99.0.

measured_thresh

Measured threshold of input file. Range is -99.0 - +0.0.

offset

Set offset gain. Gain is applied before the true-peak limiter. Range is -99.0 - +99.0. Default is +0.0.

linear

Normalize linearly if possible. measured_I, measured_LRA, measured_TP, and measured_thresh must also to be specified in order to use this mode. Options are true or false. Default is true.

dual_mono

Treat mono input files as "dual-mono". If a mono file is intended for playback on a stereo system, its EBU R128 measurement will be perceptually incorrect. If set to true, this option will compensate for this effect. Multi-channel input files are not affected by this option. Options are true or false. Default is false.

print_format

Set print format for stats. Options are summary, json, or none. Default value is none.

6.49 lowpass

Apply a low-pass filter with 3dB point frequency. The filter can be either single-pole or double-pole (the default). The filter roll off at 6dB per pole per octave (20dB per pole per decade).

The filter accepts the following options:

frequency, f

Set frequency in Hz. Default is 500.

poles, p

Set number of poles. Default is 2.

width_type

Set method to specify band-width of filter.

h

Hz

q

Q-Factor

o

octave

s

slope

width, w

Specify the band-width of a filter in width_type units. Applies only to double-pole filter. The default is 0.707q and gives a Butterworth response.

6.50 pan

Mix channels with specific gain levels. The filter accepts the output channel layout followed by a set of channels definitions.

This filter is also designed to efficiently remap the channels of an audio stream.

The filter accepts parameters of the form: "l|outdef|outdef|..."

l

output channel layout or number of channels

outdef

output channel specification, of the form: "out_name=[gain*]in_name[+[gain*]in_name...]"

out_name

output channel to define, either a channel name (FL, FR, etc.) or a channel number (c0, c1, etc.)

gain

multiplicative coefficient for the channel, 1 leaving the volume unchanged

in_name

input channel to use, see out_name for details; it is not possible to mix named and numbered input channels

If the ‘=’ in a channel specification is replaced by ‘<’, then the gains for that specification will be renormalized so that the total is 1, thus avoiding clipping noise.

6.50.1 Mixing examples

For example, if you want to down-mix from stereo to mono, but with a bigger factor for the left channel:

pan=1c|c0=0.9*c0+0.1*c1

A customized down-mix to stereo that works automatically for 3-, 4-, 5- and 7-channels surround:

pan=stereo| FL < FL + 0.5*FC + 0.6*BL + 0.6*SL | FR < FR + 0.5*FC + 0.6*BR + 0.6*SR

Note that ffmpeg integrates a default down-mix (and up-mix) system that should be preferred (see "-ac" option) unless you have very specific needs.

6.50.2 Remapping examples

The channel remapping will be effective if, and only if:

  • gain coefficients are zeroes or ones,
  • only one input per channel output,

If all these conditions are satisfied, the filter will notify the user ("Pure channel mapping detected"), and use an optimized and lossless method to do the remapping.

For example, if you have a 5.1 source and want a stereo audio stream by dropping the extra channels:

pan="stereo| c0=FL | c1=FR"

Given the same source, you can also switch front left and front right channels and keep the input channel layout:

pan="5.1| c0=c1 | c1=c0 | c2=c2 | c3=c3 | c4=c4 | c5=c5"

If the input is a stereo audio stream, you can mute the front left channel (and still keep the stereo channel layout) with:

pan="stereo|c1=c1"

Still with a stereo audio stream input, you can copy the right channel in both front left and right:

pan="stereo| c0=FR | c1=FR"

6.51 replaygain

ReplayGain scanner filter. This filter takes an audio stream as an input and outputs it unchanged. At end of filtering it displays track_gain and track_peak.

6.52 resample

Convert the audio sample format, sample rate and channel layout. It is not meant to be used directly.

6.53 rubberband

Apply time-stretching and pitch-shifting with librubberband.

The filter accepts the following options:

tempo

Set tempo scale factor.

pitch

Set pitch scale factor.

transients

Set transients detector. Possible values are:

crisp
mixed
smooth
detector

Set detector. Possible values are:

compound
percussive
soft
phase

Set phase. Possible values are:

laminar
independent
window

Set processing window size. Possible values are:

standard
short
long
smoothing

Set smoothing. Possible values are:

off
on
formant

Enable formant preservation when shift pitching. Possible values are:

shifted
preserved
pitchq

Set pitch quality. Possible values are:

quality
speed
consistency
channels

Set channels. Possible values are:

apart
together

6.54 sidechaincompress

This filter acts like normal compressor but has the ability to compress detected signal using second input signal. It needs two input streams and returns one output stream. First input stream will be processed depending on second stream signal. The filtered signal then can be filtered with other filters in later stages of processing. See pan and amerge filter.

The filter accepts the following options:

level_in

Set input gain. Default is 1. Range is between 0.015625 and 64.

threshold

If a signal of second stream raises above this level it will affect the gain reduction of first stream. By default is 0.125. Range is between 0.00097563 and 1.

ratio

Set a ratio about which the signal is reduced. 1:2 means that if the level raised 4dB above the threshold, it will be only 2dB above after the reduction. Default is 2. Range is between 1 and 20.

attack

Amount of milliseconds the signal has to rise above the threshold before gain reduction starts. Default is 20. Range is between 0.01 and 2000.

release

Amount of milliseconds the signal has to fall below the threshold before reduction is decreased again. Default is 250. Range is between 0.01 and 9000.

makeup

Set the amount by how much signal will be amplified after processing. Default is 2. Range is from 1 and 64.

knee

Curve the sharp knee around the threshold to enter gain reduction more softly. Default is 2.82843. Range is between 1 and 8.

link

Choose if the average level between all channels of side-chain stream or the louder(maximum) channel of side-chain stream affects the reduction. Default is average.

detection

Should the exact signal be taken in case of peak or an RMS one in case of rms. Default is rms which is mainly smoother.

level_sc

Set sidechain gain. Default is 1. Range is between 0.015625 and 64.

mix

How much to use compressed signal in output. Default is 1. Range is between 0 and 1.

6.54.1 Examples

  • Full ffmpeg example taking 2 audio inputs, 1st input to be compressed depending on the signal of 2nd input and later compressed signal to be merged with 2nd input:
    ffmpeg -i main.flac -i sidechain.flac -filter_complex "[1:a]asplit=2[sc][mix];[0:a][sc]sidechaincompress[compr];[compr][mix]amerge"
    

6.55 sidechaingate

A sidechain gate acts like a normal (wideband) gate but has the ability to filter the detected signal before sending it to the gain reduction stage. Normally a gate uses the full range signal to detect a level above the threshold. For example: If you cut all lower frequencies from your sidechain signal the gate will decrease the volume of your track only if not enough highs appear. With this technique you are able to reduce the resonation of a natural drum or remove "rumbling" of muted strokes from a heavily distorted guitar. It needs two input streams and returns one output stream. First input stream will be processed depending on second stream signal.

The filter accepts the following options:

level_in

Set input level before filtering. Default is 1. Allowed range is from 0.015625 to 64.

range

Set the level of gain reduction when the signal is below the threshold. Default is 0.06125. Allowed range is from 0 to 1.

threshold

If a signal rises above this level the gain reduction is released. Default is 0.125. Allowed range is from 0 to 1.

ratio

Set a ratio about which the signal is reduced. Default is 2. Allowed range is from 1 to 9000.

attack

Amount of milliseconds the signal has to rise above the threshold before gain reduction stops. Default is 20 milliseconds. Allowed range is from 0.01 to 9000.

release

Amount of milliseconds the signal has to fall below the threshold before the reduction is increased again. Default is 250 milliseconds. Allowed range is from 0.01 to 9000.

makeup

Set amount of amplification of signal after processing. Default is 1. Allowed range is from 1 to 64.

knee

Curve the sharp knee around the threshold to enter gain reduction more softly. Default is 2.828427125. Allowed range is from 1 to 8.

detection

Choose if exact signal should be taken for detection or an RMS like one. Default is rms. Can be peak or rms.

link

Choose if the average level between all channels or the louder channel affects the reduction. Default is average. Can be average or maximum.

level_sc

Set sidechain gain. Default is 1. Range is from 0.015625 to 64.

6.56 silencedetect

Detect silence in an audio stream.

This filter logs a message when it detects that the input audio volume is less or equal to a noise tolerance value for a duration greater or equal to the minimum detected noise duration.

The printed times and duration are expressed in seconds.

The filter accepts the following options:

duration, d

Set silence duration until notification (default is 2 seconds).

noise, n

Set noise tolerance. Can be specified in dB (in case "dB" is appended to the specified value) or amplitude ratio. Default is -60dB, or 0.001.

6.56.1 Examples

  • Detect 5 seconds of silence with -50dB noise tolerance:
    silencedetect=n=-50dB:d=5
    
  • Complete example with ffmpeg to detect silence with 0.0001 noise tolerance in silence.mp3:
    ffmpeg -i silence.mp3 -af silencedetect=noise=0.0001 -f null -
    

6.57 silenceremove

Remove silence from the beginning, middle or end of the audio.

The filter accepts the following options:

start_periods

This value is used to indicate if audio should be trimmed at beginning of the audio. A value of zero indicates no silence should be trimmed from the beginning. When specifying a non-zero value, it trims audio up until it finds non-silence. Normally, when trimming silence from beginning of audio the start_periods will be 1 but it can be increased to higher values to trim all audio up to specific count of non-silence periods. Default value is 0.

start_duration

Specify the amount of time that non-silence must be detected before it stops trimming audio. By increasing the duration, bursts of noises can be treated as silence and trimmed off. Default value is 0.

start_threshold

This indicates what sample value should be treated as silence. For digital audio, a value of 0 may be fine but for audio recorded from analog, you may wish to increase the value to account for background noise. Can be specified in dB (in case "dB" is appended to the specified value) or amplitude ratio. Default value is 0.

stop_periods

Set the count for trimming silence from the end of audio. To remove silence from the middle of a file, specify a stop_periods that is negative. This value is then treated as a positive value and is used to indicate the effect should restart processing as specified by start_periods, making it suitable for removing periods of silence in the middle of the audio. Default value is 0.

stop_duration

Specify a duration of silence that must exist before audio is not copied any more. By specifying a higher duration, silence that is wanted can be left in the audio. Default value is 0.

stop_threshold

This is the same as start_threshold but for trimming silence from the end of audio. Can be specified in dB (in case "dB" is appended to the specified value) or amplitude ratio. Default value is 0.

leave_silence

This indicate that stop_duration length of audio should be left intact at the beginning of each period of silence. For example, if you want to remove long pauses between words but do not want to remove the pauses completely. Default value is 0.

detection

Set how is silence detected. Can be rms or peak. Second is faster and works better with digital silence which is exactly 0. Default value is rms.

window

Set ratio used to calculate size of window for detecting silence. Default value is 0.02. Allowed range is from 0 to 10.

6.57.1 Examples

  • The following example shows how this filter can be used to start a recording that does not contain the delay at the start which usually occurs between pressing the record button and the start of the performance:
    silenceremove=1:5:0.02
    
  • Trim all silence encountered from begining to end where there is more than 1 second of silence in audio:
    silenceremove=0:0:0:-1:1:-90dB
    

6.58 sofalizer

SOFAlizer uses head-related transfer functions (HRTFs) to create virtual loudspeakers around the user for binaural listening via headphones (audio formats up to 9 channels supported). The HRTFs are stored in SOFA files (see http://www.sofacoustics.org/ for a database). SOFAlizer is developed at the Acoustics Research Institute (ARI) of the Austrian Academy of Sciences.

To enable compilation of this filter you need to configure FFmpeg with --enable-netcdf.

The filter accepts the following options:

sofa

Set the SOFA file used for rendering.

gain

Set gain applied to audio. Value is in dB. Default is 0.

rotation

Set rotation of virtual loudspeakers in deg. Default is 0.

elevation

Set elevation of virtual speakers in deg. Default is 0.

radius

Set distance in meters between loudspeakers and the listener with near-field HRTFs. Default is 1.

type

Set processing type. Can be time or freq. time is processing audio in time domain which is slow. freq is processing audio in frequency domain which is fast. Default is freq.

speakers

Set custom positions of virtual loudspeakers. Syntax for this option is: <CH> <AZIM> <ELEV>[|<CH> <AZIM> <ELEV>|...]. Each virtual loudspeaker is described with short channel name following with azimuth and elevation in degreees. Each virtual loudspeaker description is separated by ’|’. For example to override front left and front right channel positions use: ’speakers=FL 45 15|FR 345 15’. Descriptions with unrecognised channel names are ignored.

6.58.1 Examples

  • Using ClubFritz6 sofa file:
    sofalizer=sofa=/path/to/ClubFritz6.sofa:type=freq:radius=1
    
  • Using ClubFritz12 sofa file and bigger radius with small rotation:
    sofalizer=sofa=/path/to/ClubFritz12.sofa:type=freq:radius=2:rotation=5
    
  • Similar as above but with custom speaker positions for front left, front right, rear left and rear right and also with custom gain:
    "sofalizer=sofa=/path/to/ClubFritz6.sofa:type=freq:radius=2:speakers=FL 45|FR 315|RL 135|RR 225:gain=28"
    

6.59 stereotools

This filter has some handy utilities to manage stereo signals, for converting M/S stereo recordings to L/R signal while having control over the parameters or spreading the stereo image of master track.

The filter accepts the following options:

level_in

Set input level before filtering for both channels. Defaults is 1. Allowed range is from 0.015625 to 64.

level_out

Set output level after filtering for both channels. Defaults is 1. Allowed range is from 0.015625 to 64.

balance_in

Set input balance between both channels. Default is 0. Allowed range is from -1 to 1.

balance_out

Set output balance between both channels. Default is 0. Allowed range is from -1 to 1.

softclip

Enable softclipping. Results in analog distortion instead of harsh digital 0dB clipping. Disabled by default.

mutel

Mute the left channel. Disabled by default.

muter

Mute the right channel. Disabled by default.

phasel

Change the phase of the left channel. Disabled by default.

phaser

Change the phase of the right channel. Disabled by default.

mode

Set stereo mode. Available values are:

lr>lr

Left/Right to Left/Right, this is default.

lr>ms

Left/Right to Mid/Side.

ms>lr

Mid/Side to Left/Right.

lr>ll

Left/Right to Left/Left.

lr>rr

Left/Right to Right/Right.

lr>l+r

Left/Right to Left + Right.

lr>rl

Left/Right to Right/Left.

slev

Set level of side signal. Default is 1. Allowed range is from 0.015625 to 64.

sbal

Set balance of side signal. Default is 0. Allowed range is from -1 to 1.

mlev

Set level of the middle signal. Default is 1. Allowed range is from 0.015625 to 64.

mpan

Set middle signal pan. Default is 0. Allowed range is from -1 to 1.

base

Set stereo base between mono and inversed channels. Default is 0. Allowed range is from -1 to 1.

delay

Set delay in milliseconds how much to delay left from right channel and vice versa. Default is 0. Allowed range is from -20 to 20.

sclevel

Set S/C level. Default is 1. Allowed range is from 1 to 100.

phase

Set the stereo phase in degrees. Default is 0. Allowed range is from 0 to 360.

6.59.1 Examples

  • Apply karaoke like effect:
    stereotools=mlev=0.015625
    
  • Convert M/S signal to L/R:
    "stereotools=mode=ms>lr"
    

6.60 stereowiden

This filter enhance the stereo effect by suppressing signal common to both channels and by delaying the signal of left into right and vice versa, thereby widening the stereo effect.

The filter accepts the following options:

delay

Time in milliseconds of the delay of left signal into right and vice versa. Default is 20 milliseconds.

feedback

Amount of gain in delayed signal into right and vice versa. Gives a delay effect of left signal in right output and vice versa which gives widening effect. Default is 0.3.

crossfeed

Cross feed of left into right with inverted phase. This helps in suppressing the mono. If the value is 1 it will cancel all the signal common to both channels. Default is 0.3.

drymix

Set level of input signal of original channel. Default is 0.8.

6.61 scale_npp

Use the NVIDIA Performance Primitives (libnpp) to perform scaling and/or pixel format conversion on CUDA video frames. Setting the output width and height works in the same way as for the scale filter.

The following additional options are accepted:

format

The pixel format of the output CUDA frames. If set to the string "same" (the default), the input format will be kept. Note that automatic format negotiation and conversion is not yet supported for hardware frames

interp_algo

The interpolation algorithm used for resizing. One of the following:

nn

Nearest neighbour.

linear
cubic
cubic2p_bspline

2-parameter cubic (B=1, C=0)

cubic2p_catmullrom

2-parameter cubic (B=0, C=1/2)

cubic2p_b05c03

2-parameter cubic (B=1/2, C=3/10)

super

Supersampling

lanczos

6.62 select

Select frames to pass in output.

6.63 treble

Boost or cut treble (upper) frequencies of the audio using a two-pole shelving filter with a response similar to that of a standard hi-fi’s tone-controls. This is also known as shelving equalisation (EQ).

The filter accepts the following options:

gain, g

Give the gain at whichever is the lower of ~22 kHz and the Nyquist frequency. Its useful range is about -20 (for a large cut) to +20 (for a large boost). Beware of clipping when using a positive gain.

frequency, f

Set the filter’s central frequency and so can be used to extend or reduce the frequency range to be boosted or cut. The default value is 3000 Hz.

width_type

Set method to specify band-width of filter.

h

Hz

q

Q-Factor

o

octave

s

slope

width, w

Determine how steep is the filter’s shelf transition.

6.64 tremolo

Sinusoidal amplitude modulation.

The filter accepts the following options:

f

Modulation frequency in Hertz. Modulation frequencies in the subharmonic range (20 Hz or lower) will result in a tremolo effect. This filter may also be used as a ring modulator by specifying a modulation frequency higher than 20 Hz. Range is 0.1 - 20000.0. Default value is 5.0 Hz.

d

Depth of modulation as a percentage. Range is 0.0 - 1.0. Default value is 0.5.

6.65 vibrato

Sinusoidal phase modulation.

The filter accepts the following options:

f

Modulation frequency in Hertz. Range is 0.1 - 20000.0. Default value is 5.0 Hz.

d

Depth of modulation as a percentage. Range is 0.0 - 1.0. Default value is 0.5.

6.66 volume

Adjust the input audio volume.

It accepts the following parameters:

volume

Set audio volume expression.

Output values are clipped to the maximum value.

The output audio volume is given by the relation:

output_volume = volume * input_volume

The default value for volume is "1.0".

precision

This parameter represents the mathematical precision.

It determines which input sample formats will be allowed, which affects the precision of the volume scaling.

fixed

8-bit fixed-point; this limits input sample format to U8, S16, and S32.

float

32-bit floating-point; this limits input sample format to FLT. (default)

double

64-bit floating-point; this limits input sample format to DBL.

replaygain

Choose the behaviour on encountering ReplayGain side data in input frames.

drop

Remove ReplayGain side data, ignoring its contents (the default).

ignore

Ignore ReplayGain side data, but leave it in the frame.

track

Prefer the track gain, if present.

album

Prefer the album gain, if present.

replaygain_preamp

Pre-amplification gain in dB to apply to the selected replaygain gain.

Default value for replaygain_preamp is 0.0.

eval

Set when the volume expression is evaluated.

It accepts the following values:

once

only evaluate expression once during the filter initialization, or when the ‘volume’ command is sent

frame

evaluate expression for each incoming frame

Default value is ‘once’.

The volume expression can contain the following parameters.

n

frame number (starting at zero)

nb_channels

number of channels

nb_consumed_samples

number of samples consumed by the filter

nb_samples

number of samples in the current frame

pos

original frame position in the file

pts

frame PTS

sample_rate

sample rate

startpts

PTS at start of stream

startt

time at start of stream

t

frame time

tb

timestamp timebase

volume

last set volume value

Note that when eval is set to ‘once’ only the sample_rate and tb variables are available, all other variables will evaluate to NAN.

6.66.1 Commands

This filter supports the following commands:

volume

Modify the volume expression. The command accepts the same syntax of the corresponding option.

If the specified expression is not valid, it is kept at its current value.

replaygain_noclip

Prevent clipping by limiting the gain applied.

Default value for replaygain_noclip is 1.

6.66.2 Examples

  • Halve the input audio volume:
    volume=volume=0.5
    volume=volume=1/2
    volume=volume=-6.0206dB
    

    In all the above example the named key for volume can be omitted, for example like in:

    volume=0.5
    
  • Increase input audio power by 6 decibels using fixed-point precision:
    volume=volume=6dB:precision=fixed
    
  • Fade volume after time 10 with an annihilation period of 5 seconds:
    volume='if(lt(t,10),1,max(1-(t-10)/5,0))':eval=frame
    

6.67 volumedetect

Detect the volume of the input video.

The filter has no parameters. The input is not modified. Statistics about the volume will be printed in the log when the input stream end is reached.

In particular it will show the mean volume (root mean square), maximum volume (on a per-sample basis), and the beginning of a histogram of the registered volume values (from the maximum value to a cumulated 1/1000 of the samples).

All volumes are in decibels relative to the maximum PCM value.

6.67.1 Examples

Here is an excerpt of the output:

[Parsed_volumedetect_0  0xa23120] mean_volume: -27 dB
[Parsed_volumedetect_0  0xa23120] max_volume: -4 dB
[Parsed_volumedetect_0  0xa23120] histogram_4db: 6
[Parsed_volumedetect_0  0xa23120] histogram_5db: 62
[Parsed_volumedetect_0  0xa23120] histogram_6db: 286
[Parsed_volumedetect_0  0xa23120] histogram_7db: 1042
[Parsed_volumedetect_0  0xa23120] histogram_8db: 2551
[Parsed_volumedetect_0  0xa23120] histogram_9db: 4609
[Parsed_volumedetect_0  0xa23120] histogram_10db: 8409

It means that:

  • The mean square energy is approximately -27 dB, or 10^-2.7.
  • The largest sample is at -4 dB, or more precisely between -4 dB and -5 dB.
  • There are 6 samples at -4 dB, 62 at -5 dB, 286 at -6 dB, etc.

In other words, raising the volume by +4 dB does not cause any clipping, raising it by +5 dB causes clipping for 6 samples, etc.

7 Audio Sources

Below is a description of the currently available audio sources.

7.1 abuffer

Buffer audio frames, and make them available to the filter chain.

This source is mainly intended for a programmatic use, in particular through the interface defined in libavfilter/asrc_abuffer.h.

It accepts the following parameters:

time_base

The timebase which will be used for timestamps of submitted frames. It must be either a floating-point number or in numerator/denominator form.

sample_rate

The sample rate of the incoming audio buffers.

sample_fmt

The sample format of the incoming audio buffers. Either a sample format name or its corresponding integer representation from the enum AVSampleFormat in libavutil/samplefmt.h

channel_layout

The channel layout of the incoming audio buffers. Either a channel layout name from channel_layout_map in libavutil/channel_layout.c or its corresponding integer representation from the AV_CH_LAYOUT_* macros in libavutil/channel_layout.h

channels

The number of channels of the incoming audio buffers. If both channels and channel_layout are specified, then they must be consistent.

7.1.1 Examples

abuffer=sample_rate=44100:sample_fmt=s16p:channel_layout=stereo

will instruct the source to accept planar 16bit signed stereo at 44100Hz. Since the sample format with name "s16p" corresponds to the number 6 and the "stereo" channel layout corresponds to the value 0x3, this is equivalent to:

abuffer=sample_rate=44100:sample_fmt=6:channel_layout=0x3

7.2 aevalsrc

Generate an audio signal specified by an expression.

This source accepts in input one or more expressions (one for each channel), which are evaluated and used to generate a corresponding audio signal.

This source accepts the following options:

exprs

Set the ’|’-separated expressions list for each separate channel. In case the channel_layout option is not specified, the selected channel layout depends on the number of provided expressions. Otherwise the last specified expression is applied to the remaining output channels.

channel_layout, c

Set the channel layout. The number of channels in the specified layout must be equal to the number of specified expressions.

duration, d

Set the minimum duration of the sourced audio. See (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax. Note that the resulting duration may be greater than the specified duration, as the generated audio is always cut at the end of a complete frame.

If not specified, or the expressed duration is negative, the audio is supposed to be generated forever.

nb_samples, n

Set the number of samples per channel per each output frame, default to 1024.

sample_rate, s

Specify the sample rate, default to 44100.

Each expression in exprs can contain the following constants:

n

number of the evaluated sample, starting from 0

t

time of the evaluated sample expressed in seconds, starting from 0

s

sample rate

7.2.1 Examples

  • Generate silence:
    aevalsrc=0
    
  • Generate a sin signal with frequency of 440 Hz, set sample rate to 8000 Hz:
    aevalsrc="sin(440*2*PI*t):s=8000"
    
  • Generate a two channels signal, specify the channel layout (Front Center + Back Center) explicitly:
    aevalsrc="sin(420*2*PI*t)|cos(430*2*PI*t):c=FC|BC"
    
  • Generate white noise:
    aevalsrc="-2+random(0)"
    
  • Generate an amplitude modulated signal:
    aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)"
    
  • Generate 2.5 Hz binaural beats on a 360 Hz carrier:
    aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) | 0.1*sin(2*PI*(360+2.5/2)*t)"
    

7.3 anullsrc

The null audio source, return unprocessed audio frames. It is mainly useful as a template and to be employed in analysis / debugging tools, or as the source for filters which ignore the input data (for example the sox synth filter).

This source accepts the following options:

channel_layout, cl

Specifies the channel layout, and can be either an integer or a string representing a channel layout. The default value of channel_layout is "stereo".

Check the channel_layout_map definition in libavutil/channel_layout.c for the mapping between strings and channel layout values.

sample_rate, r

Specifies the sample rate, and defaults to 44100.

nb_samples, n

Set the number of samples per requested frames.

7.3.1 Examples

  • Set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO.
    anullsrc=r=48000:cl=4
    
  • Do the same operation with a more obvious syntax:
    anullsrc=r=48000:cl=mono
    

All the parameters need to be explicitly defined.

7.4 flite

Synthesize a voice utterance using the libflite library.

To enable compilation of this filter you need to configure FFmpeg with --enable-libflite.

Note that the flite library is not thread-safe.

The filter accepts the following options:

list_voices

If set to 1, list the names of the available voices and exit immediately. Default value is 0.

nb_samples, n

Set the maximum number of samples per frame. Default value is 512.

textfile

Set the filename containing the text to speak.

text

Set the text to speak.

voice, v

Set the voice to use for the speech synthesis. Default value is kal. See also the list_voices option.

7.4.1 Examples

  • Read from file speech.txt, and synthesize the text using the standard flite voice:
    flite=textfile=speech.txt
    
  • Read the specified text selecting the slt voice:
    flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
    
  • Input text to ffmpeg:
    ffmpeg -f lavfi -i flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
    
  • Make ffplay speak the specified text, using flite and the lavfi device:
    ffplay -f lavfi flite=text='No more be grieved for which that thou hast done.'
    

For more information about libflite, check: http://www.speech.cs.cmu.edu/flite/

7.5 anoisesrc

Generate a noise audio signal.

The filter accepts the following options:

sample_rate, r

Specify the sample rate. Default value is 48000 Hz.

amplitude, a

Specify the amplitude (0.0 - 1.0) of the generated audio stream. Default value is 1.0.

duration, d

Specify the duration of the generated audio stream. Not specifying this option results in noise with an infinite length.

color, colour, c

Specify the color of noise. Available noise colors are white, pink, and brown. Default color is white.

seed, s

Specify a value used to seed the PRNG.

nb_samples, n

Set the number of samples per each output frame, default is 1024.

7.5.1 Examples

  • Generate 60 seconds of pink noise, with a 44.1 kHz sampling rate and an amplitude of 0.5:
    anoisesrc=d=60:c=pink:r=44100:a=0.5
    

7.6 sine

Generate an audio signal made of a sine wave with amplitude 1/8.

The audio signal is bit-exact.

The filter accepts the following options:

frequency, f

Set the carrier frequency. Default is 440 Hz.

beep_factor, b

Enable a periodic beep every second with frequency beep_factor times the carrier frequency. Default is 0, meaning the beep is disabled.

sample_rate, r

Specify the sample rate, default is 44100.

duration, d

Specify the duration of the generated audio stream.

samples_per_frame

Set the number of samples per output frame.

The expression can contain the following constants:

n

The (sequential) number of the output audio frame, starting from 0.

pts

The PTS (Presentation TimeStamp) of the output audio frame, expressed in TB units.

t

The PTS of the output audio frame, expressed in seconds.

TB

The timebase of the output audio frames.

Default is 1024.

7.6.1 Examples

  • Generate a simple 440 Hz sine wave:
    sine
    
  • Generate a 220 Hz sine wave with a 880 Hz beep each second, for 5 seconds:
    sine=220:4:d=5
    sine=f=220:b=4:d=5
    sine=frequency=220:beep_factor=4:duration=5
    
  • Generate a 1 kHz sine wave following 1602,1601,1602,1601,1602 NTSC pattern:
    sine=1000:samples_per_frame='st(0,mod(n,5)); 1602-not(not(eq(ld(0),1)+eq(ld(0),3)))'
    

8 Audio Sinks

Below is a description of the currently available audio sinks.

8.1 abuffersink

Buffer audio frames, and make them available to the end of filter chain.

This sink is mainly intended for programmatic use, in particular through the interface defined in libavfilter/buffersink.h or the options system.

It accepts a pointer to an AVABufferSinkContext structure, which defines the incoming buffers’ formats, to be passed as the opaque parameter to avfilter_init_filter for initialization.

8.2 anullsink

Null audio sink; do absolutely nothing with the input audio. It is mainly useful as a template and for use in analysis / debugging tools.

9 Video Filters

When you configure your FFmpeg build, you can disable any of the existing filters using --disable-filters. The configure output will show the video filters included in your build.

Below is a description of the currently available video filters.

9.1 alphaextract

Extract the alpha component from the input as a grayscale video. This is especially useful with the alphamerge filter.

9.2 alphamerge

Add or replace the alpha component of the primary input with the grayscale value of a second input. This is intended for use with alphaextract to allow the transmission or storage of frame sequences that have alpha in a format that doesn’t support an alpha channel.

For example, to reconstruct full frames from a normal YUV-encoded video and a separate video created with alphaextract, you might use:

movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out]

Since this filter is designed for reconstruction, it operates on frame sequences without considering timestamps, and terminates when either input reaches end of stream. This will cause problems if your encoding pipeline drops frames. If you’re trying to apply an image as an overlay to a video stream, consider the overlay filter instead.

9.3 ass

Same as the subtitles filter, except that it doesn’t require libavcodec and libavformat to work. On the other hand, it is limited to ASS (Advanced Substation Alpha) subtitles files.

This filter accepts the following option in addition to the common options from the subtitles filter:

shaping

Set the shaping engine

Available values are:

auto

The default libass shaping engine, which is the best available.

simple

Fast, font-agnostic shaper that can do only substitutions

complex

Slower shaper using OpenType for substitutions and positioning

The default is auto.

9.4 atadenoise

Apply an Adaptive Temporal Averaging Denoiser to the video input.

The filter accepts the following options:

0a

Set threshold A for 1st plane. Default is 0.02. Valid range is 0 to 0.3.

0b

Set threshold B for 1st plane. Default is 0.04. Valid range is 0 to 5.

1a

Set threshold A for 2nd plane. Default is 0.02. Valid range is 0 to 0.3.

1b

Set threshold B for 2nd plane. Default is 0.04. Valid range is 0 to 5.

2a

Set threshold A for 3rd plane. Default is 0.02. Valid range is 0 to 0.3.

2b

Set threshold B for 3rd plane. Default is 0.04. Valid range is 0 to 5.

Threshold A is designed to react on abrupt changes in the input signal and threshold B is designed to react on continuous changes in the input signal.

s

Set number of frames filter will use for averaging. Default is 33. Must be odd number in range [5, 129].

9.5 bbox

Compute the bounding box for the non-black pixels in the input frame luminance plane.

This filter computes the bounding box containing all the pixels with a luminance value greater than the minimum allowed value. The parameters describing the bounding box are printed on the filter log.

The filter accepts the following option:

min_val

Set the minimal luminance value. Default is 16.

9.6 blackdetect

Detect video intervals that are (almost) completely black. Can be useful to detect chapter transitions, commercials, or invalid recordings. Output lines contains the time for the start, end and duration of the detected black interval expressed in seconds.

In order to display the output lines, you need to set the loglevel at least to the AV_LOG_INFO value.

The filter accepts the following options:

black_min_duration, d

Set the minimum detected black duration expressed in seconds. It must be a non-negative floating point number.

Default value is 2.0.

picture_black_ratio_th, pic_th

Set the threshold for considering a picture "black". Express the minimum value for the ratio:

nb_black_pixels / nb_pixels

for which a picture is considered black. Default value is 0.98.

pixel_black_th, pix_th

Set the threshold for considering a pixel "black".

The threshold expresses the maximum pixel luminance value for which a pixel is considered "black". The provided value is scaled according to the following equation:

absolute_threshold = luminance_minimum_value + pixel_black_th * luminance_range_size

luminance_range_size and luminance_minimum_value depend on the input video format, the range is [0-255] for YUV full-range formats and [16-235] for YUV non full-range formats.

Default value is 0.10.

The following example sets the maximum pixel threshold to the minimum value, and detects only black intervals of 2 or more seconds:

blackdetect=d=2:pix_th=0.00

9.7 blackframe

Detect frames that are (almost) completely black. Can be useful to detect chapter transitions or commercials. Output lines consist of the frame number of the detected frame, the percentage of blackness, the position in the file if known or -1 and the timestamp in seconds.

In order to display the output lines, you need to set the loglevel at least to the AV_LOG_INFO value.

It accepts the following parameters:

amount

The percentage of the pixels that have to be below the threshold; it defaults to 98.

threshold, thresh

The threshold below which a pixel value is considered black; it defaults to 32.

9.8 blend, tblend

Blend two video frames into each other.

The blend filter takes two input streams and outputs one stream, the first input is the "top" layer and second input is "bottom" layer. Output terminates when shortest input terminates.

The tblend (time blend) filter takes two consecutive frames from one single stream, and outputs the result obtained by blending the new frame on top of the old frame.

A description of the accepted options follows.

c0_mode
c1_mode
c2_mode
c3_mode
all_mode

Set blend mode for specific pixel component or all pixel components in case of all_mode. Default value is normal.

Available values for component modes are:

addition
addition128
and
average
burn
darken
difference
difference128
divide
dodge
freeze
exclusion
glow
hardlight
hardmix
heat
lighten
linearlight
multiply
multiply128
negation
normal
or
overlay
phoenix
pinlight
reflect
screen
softlight
subtract
vividlight
xor
c0_opacity
c1_opacity
c2_opacity
c3_opacity
all_opacity

Set blend opacity for specific pixel component or all pixel components in case of all_opacity. Only used in combination with pixel component blend modes.

c0_expr
c1_expr
c2_expr
c3_expr
all_expr

Set blend expression for specific pixel component or all pixel components in case of all_expr. Note that related mode options will be ignored if those are set.

The expressions can use the following variables:

N

The sequential number of the filtered frame, starting from 0.

X
Y

the coordinates of the current sample

W
H

the width and height of currently filtered plane

SW
SH

Width and height scale depending on the currently filtered plane. It is the ratio between the corresponding luma plane number of pixels and the current plane ones. E.g. for YUV4:2:0 the values are 1,1 for the luma plane, and 0.5,0.5 for chroma planes.

T

Time of the current frame, expressed in seconds.

TOP, A

Value of pixel component at current location for first video frame (top layer).

BOTTOM, B

Value of pixel component at current location for second video frame (bottom layer).

shortest

Force termination when the shortest input terminates. Default is 0. This option is only defined for the blend filter.

repeatlast

Continue applying the last bottom frame after the end of the stream. A value of 0 disable the filter after the last frame of the bottom layer is reached. Default is 1. This option is only defined for the blend filter.

9.8.1 Examples

  • Apply transition from bottom layer to top layer in first 10 seconds:
    blend=all_expr='A*(if(gte(T,10),1,T/10))+B*(1-(if(gte(T,10),1,T/10)))'
    
  • Apply 1x1 checkerboard effect:
    blend=all_expr='if(eq(mod(X,2),mod(Y,2)),A,B)'
    
  • Apply uncover left effect:
    blend=all_expr='if(gte(N*SW+X,W),A,B)'
    
  • Apply uncover down effect:
    blend=all_expr='if(gte(Y-N*SH,0),A,B)'
    
  • Apply uncover up-left effect:
    blend=all_expr='if(gte(T*SH*40+Y,H)*gte((T*40*SW+X)*W/H,W),A,B)'
    
  • Split diagonally video and shows top and bottom layer on each side:
    blend=all_expr=if(gt(X,Y*(W/H)),A,B)
    
  • Display differences between the current and the previous frame:
    tblend=all_mode=difference128
    

9.9 boxblur

Apply a boxblur algorithm to the input video.

It accepts the following parameters:

luma_radius, lr
luma_power, lp
chroma_radius, cr
chroma_power, cp
alpha_radius, ar
alpha_power, ap

A description of the accepted options follows.

luma_radius, lr
chroma_radius, cr
alpha_radius, ar

Set an expression for the box radius in pixels used for blurring the corresponding input plane.

The radius value must be a non-negative number, and must not be greater than the value of the expression min(w,h)/2 for the luma and alpha planes, and of min(cw,ch)/2 for the chroma planes.

Default value for luma_radius is "2". If not specified, chroma_radius and alpha_radius default to the corresponding value set for luma_radius.

The expressions can contain the following constants:

w
h

The input width and height in pixels.

cw
ch

The input chroma image width and height in pixels.

hsub
vsub

The horizontal and vertical chroma subsample values. For example, for the pixel format "yuv422p", hsub is 2 and vsub is 1.

luma_power, lp
chroma_power, cp
alpha_power, ap

Specify how many times the boxblur filter is applied to the corresponding plane.

Default value for luma_power is 2. If not specified, chroma_power and alpha_power default to the corresponding value set for luma_power.

A value of 0 will disable the effect.

9.9.1 Examples

  • Apply a boxblur filter with the luma, chroma, and alpha radii set to 2:
    boxblur=luma_radius=2:luma_power=1
    boxblur=2:1
    
  • Set the luma radius to 2, and alpha and chroma radius to 0:
    boxblur=2:1:cr=0:ar=0
    
  • Set the luma and chroma radii to a fraction of the video dimension:
    boxblur=luma_radius=min(h\,w)/10:luma_power=1:chroma_radius=min(cw\,ch)/10:chroma_power=1
    

9.10 bwdif

Deinterlace the input video ("bwdif" stands for "Bob Weaver Deinterlacing Filter").

Motion adaptive deinterlacing based on yadif with the use of w3fdif and cubic interpolation algorithms. It accepts the following parameters:

mode

The interlacing mode to adopt. It accepts one of the following values:

0, send_frame

Output one frame for each frame.

1, send_field

Output one frame for each field.

The default value is send_field.

parity

The picture field parity assumed for the input interlaced video. It accepts one of the following values:

0, tff

Assume the top field is first.

1, bff

Assume the bottom field is first.

-1, auto

Enable automatic detection of field parity.

The default value is auto. If the interlacing is unknown or the decoder does not export this information, top field first will be assumed.

deint

Specify which frames to deinterlace. Accept one of the following values:

0, all

Deinterlace all frames.

1, interlaced

Only deinterlace frames marked as interlaced.

The default value is all.

9.11 chromakey

YUV colorspace color/chroma keying.

The filter accepts the following options:

color

The color which will be replaced with transparency.

similarity

Similarity percentage with the key color.

0.01 matches only the exact key color, while 1.0 matches everything.

blend

Blend percentage.

0.0 makes pixels either fully transparent, or not transparent at all.

Higher values result in semi-transparent pixels, with a higher transparency the more similar the pixels color is to the key color.

yuv

Signals that the color passed is already in YUV instead of RGB.

Litteral colors like "green" or "red" don’t make sense with this enabled anymore. This can be used to pass exact YUV values as hexadecimal numbers.

9.11.1 Examples

  • Make every green pixel in the input image transparent:
    ffmpeg -i input.png -vf chromakey=green out.png
    
  • Overlay a greenscreen-video on top of a static black background.
    ffmpeg -f lavfi -i color=c=black:s=1280x720 -i video.mp4 -shortest -filter_complex "[1:v]chromakey=0x70de77:0.1:0.2[ckout];[0:v][ckout]overlay[out]" -map "[out]" output.mkv
    

9.12 ciescope

Display CIE color diagram with pixels overlaid onto it.

The filter acccepts the following options:

system

Set color system.

ntsc, 470m
ebu, 470bg
smpte
240m
apple
widergb
cie1931
rec709, hdtv
uhdtv, rec2020
cie

Set CIE system.

xyy
ucs
luv
gamuts

Set what gamuts to draw.

See system option for avaiable values.

size, s

Set ciescope size, by default set to 512.

intensity, i

Set intensity used to map input pixel values to CIE diagram.

contrast

Set contrast used to draw tongue colors that are out of active color system gamut.

corrgamma

Correct gamma displayed on scope, by default enabled.

showwhite

Show white point on CIE diagram, by default disabled.

gamma

Set input gamma. Used only with XYZ input color space.

9.13 codecview

Visualize information exported by some codecs.

Some codecs can export information through frames using side-data or other means. For example, some MPEG based codecs export motion vectors through the export_mvs flag in the codec flags2 option.

The filter accepts the following option:

mv

Set motion vectors to visualize.

Available flags for mv are:

pf

forward predicted MVs of P-frames

bf

forward predicted MVs of B-frames

bb

backward predicted MVs of B-frames

qp

Display quantization parameters using the chroma planes.

mv_type, mvt

Set motion vectors type to visualize. Includes MVs from all frames unless specified by frame_type option.

Available flags for mv_type are:

fp

forward predicted MVs

bp

backward predicted MVs

frame_type, ft

Set frame type to visualize motion vectors of.

Available flags for frame_type are:

if

intra-coded frames (I-frames)

pf

predicted frames (P-frames)

bf

bi-directionally predicted frames (B-frames)

9.13.1 Examples

  • Visualize forward predicted MVs of all frames using ffplay:
    ffplay -flags2 +export_mvs input.mp4 -vf codecview=mv_type=fp
    
  • Visualize multi-directionals MVs of P and B-Frames using ffplay:
    ffplay -flags2 +export_mvs input.mp4 -vf codecview=mv=pf+bf+bb
    

9.14 colorbalance

Modify intensity of primary colors (red, green and blue) of input frames.

The filter allows an input frame to be adjusted in the shadows, midtones or highlights regions for the red-cyan, green-magenta or blue-yellow balance.

A positive adjustment value shifts the balance towards the primary color, a negative value towards the complementary color.

The filter accepts the following options:

rs
gs
bs

Adjust red, green and blue shadows (darkest pixels).

rm
gm
bm

Adjust red, green and blue midtones (medium pixels).

rh
gh
bh

Adjust red, green and blue highlights (brightest pixels).

Allowed ranges for options are [-1.0, 1.0]. Defaults are 0.

9.14.1 Examples

  • Add red color cast to shadows:
    colorbalance=rs=.3
    

9.15 colorkey

RGB colorspace color keying.

The filter accepts the following options:

color

The color which will be replaced with transparency.

similarity

Similarity percentage with the key color.

0.01 matches only the exact key color, while 1.0 matches everything.

blend

Blend percentage.

0.0 makes pixels either fully transparent, or not transparent at all.

Higher values result in semi-transparent pixels, with a higher transparency the more similar the pixels color is to the key color.

9.15.1 Examples

  • Make every green pixel in the input image transparent:
    ffmpeg -i input.png -vf colorkey=green out.png
    
  • Overlay a greenscreen-video on top of a static background image.
    ffmpeg -i background.png -i video.mp4 -filter_complex "[1:v]colorkey=0x3BBD1E:0.3:0.2[ckout];[0:v][ckout]overlay[out]" -map "[out]" output.flv
    

9.16 colorlevels

Adjust video input frames using levels.

The filter accepts the following options:

rimin
gimin
bimin
aimin

Adjust red, green, blue and alpha input black point. Allowed ranges for options are [-1.0, 1.0]. Defaults are 0.

rimax
gimax
bimax
aimax

Adjust red, green, blue and alpha input white point. Allowed ranges for options are [-1.0, 1.0]. Defaults are 1.

Input levels are used to lighten highlights (bright tones), darken shadows (dark tones), change the balance of bright and dark tones.

romin
gomin
bomin
aomin

Adjust red, green, blue and alpha output black point. Allowed ranges for options are [0, 1.0]. Defaults are 0.

romax
gomax
bomax
aomax

Adjust red, green, blue and alpha output white point. Allowed ranges for options are [0, 1.0]. Defaults are 1.

Output levels allows manual selection of a constrained output level range.

9.16.1 Examples

  • Make video output darker:
    colorlevels=rimin=0.058:gimin=0.058:bimin=0.058
    
  • Increase contrast:
    colorlevels=rimin=0.039:gimin=0.039:bimin=0.039:rimax=0.96:gimax=0.96:bimax=0.96
    
  • Make video output lighter:
    colorlevels=rimax=0.902:gimax=0.902:bimax=0.902
    
  • Increase brightness:
    colorlevels=romin=0.5:gomin=0.5:bomin=0.5
    

9.17 colorchannelmixer

Adjust video input frames by re-mixing color channels.

This filter modifies a color channel by adding the values associated to the other channels of the same pixels. For example if the value to modify is red, the output value will be:

red=red*rr + blue*rb + green*rg + alpha*ra

The filter accepts the following options:

rr
rg
rb
ra

Adjust contribution of input red, green, blue and alpha channels for output red channel. Default is 1 for rr, and 0 for rg, rb and ra.

gr
gg
gb
ga

Adjust contribution of input red, green, blue and alpha channels for output green channel. Default is 1 for gg, and 0 for gr, gb and ga.

br
bg
bb
ba

Adjust contribution of input red, green, blue and alpha channels for output blue channel. Default is 1 for bb, and 0 for br, bg and ba.

ar
ag
ab
aa

Adjust contribution of input red, green, blue and alpha channels for output alpha channel. Default is 1 for aa, and 0 for ar, ag and ab.

Allowed ranges for options are [-2.0, 2.0].

9.17.1 Examples

  • Convert source to grayscale:
    colorchannelmixer=.3:.4:.3:0:.3:.4:.3:0:.3:.4:.3
    
  • Simulate sepia tones:
    colorchannelmixer=.393:.769:.189:0:.349:.686:.168:0:.272:.534:.131
    

9.18 colormatrix

Convert color matrix.

The filter accepts the following options:

src
dst

Specify the source and destination color matrix. Both values must be specified.

The accepted values are:

bt709

BT.709

bt601

BT.601

smpte240m

SMPTE-240M

fcc

FCC

bt2020

BT.2020

For example to convert from BT.601 to SMPTE-240M, use the command:

colormatrix=bt601:smpte240m

9.19 colorspace

Convert colorspace, transfer characteristics or color primaries.

The filter accepts the following options:

all

Specify all color properties at once.

The accepted values are:

bt470m

BT.470M

bt470bg

BT.470BG

bt601-6-525

BT.601-6 525

bt601-6-625

BT.601-6 625

bt709

BT.709

smpte170m

SMPTE-170M

smpte240m

SMPTE-240M

bt2020

BT.2020

space

Specify output colorspace.

The accepted values are:

bt709

BT.709

fcc

FCC

bt470bg

BT.470BG or BT.601-6 625

smpte170m

SMPTE-170M or BT.601-6 525

smpte240m

SMPTE-240M

bt2020ncl

BT.2020 with non-constant luminance

trc

Specify output transfer characteristics.

The accepted values are:

bt709

BT.709

gamma22

Constant gamma of 2.2

gamma28

Constant gamma of 2.8

smpte170m

SMPTE-170M, BT.601-6 625 or BT.601-6 525

smpte240m

SMPTE-240M

bt2020-10

BT.2020 for 10-bits content

bt2020-12

BT.2020 for 12-bits content

prm

Specify output color primaries.

The accepted values are:

bt709

BT.709

bt470m

BT.470M

bt470bg

BT.470BG or BT.601-6 625

smpte170m

SMPTE-170M or BT.601-6 525

smpte240m

SMPTE-240M

bt2020

BT.2020

rng

Specify output color range.

The accepted values are:

mpeg

MPEG (restricted) range

jpeg

JPEG (full) range

format

Specify output color format.

The accepted values are:

yuv420p

YUV 4:2:0 planar 8-bits

yuv420p10

YUV 4:2:0 planar 10-bits

yuv420p12

YUV 4:2:0 planar 12-bits

yuv422p

YUV 4:2:2 planar 8-bits

yuv422p10

YUV 4:2:2 planar 10-bits

yuv422p12

YUV 4:2:2 planar 12-bits

yuv444p

YUV 4:4:4 planar 8-bits

yuv444p10

YUV 4:4:4 planar 10-bits

yuv444p12

YUV 4:4:4 planar 12-bits

fast

Do a fast conversion, which skips gamma/primary correction. This will take significantly less CPU, but will be mathematically incorrect. To get output compatible with that produced by the colormatrix filter, use fast=1.

dither

Specify dithering mode.

The accepted values are:

none

No dithering

fsb

Floyd-Steinberg dithering

wpadapt

Whitepoint adaptation mode.

The accepted values are:

bradford

Bradford whitepoint adaptation

vonkries

von Kries whitepoint adaptation

identity

identity whitepoint adaptation (i.e. no whitepoint adaptation)

The filter converts the transfer characteristics, color space and color primaries to the specified user values. The output value, if not specified, is set to a default value based on the "all" property. If that property is also not specified, the filter will log an error. The output color range and format default to the same value as the input color range and format. The input transfer characteristics, color space, color primaries and color range should be set on the input data. If any of these are missing, the filter will log an error and no conversion will take place.

For example to convert the input to SMPTE-240M, use the command:

colorspace=smpte240m

9.20 convolution

Apply convolution 3x3 or 5x5 filter.

The filter accepts the following options:

0m
1m
2m
3m

Set matrix for each plane. Matrix is sequence of 9 or 25 signed integers.

0rdiv
1rdiv
2rdiv
3rdiv

Set multiplier for calculated value for each plane.

0bias
1bias
2bias
3bias

Set bias for each plane. This value is added to the result of the multiplication. Useful for making the overall image brighter or darker. Default is 0.0.

9.20.1 Examples

  • Apply sharpen:
    convolution="0 -1 0 -1 5 -1 0 -1 0:0 -1 0 -1 5 -1 0 -1 0:0 -1 0 -1 5 -1 0 -1 0:0 -1 0 -1 5 -1 0 -1 0"
    
  • Apply blur:
    convolution="1 1 1 1 1 1 1 1 1:1 1 1 1 1 1 1 1 1:1 1 1 1 1 1 1 1 1:1 1 1 1 1 1 1 1 1:1/9:1/9:1/9:1/9"
    
  • Apply edge enhance:
    convolution="0 0 0 -1 1 0 0 0 0:0 0 0 -1 1 0 0 0 0:0 0 0 -1 1 0 0 0 0:0 0 0 -1 1 0 0 0 0:5:1:1:1:0:128:128:128"
    
  • Apply edge detect:
    convolution="0 1 0 1 -4 1 0 1 0:0 1 0 1 -4 1 0 1 0:0 1 0 1 -4 1 0 1 0:0 1 0 1 -4 1 0 1 0:5:5:5:1:0:128:128:128"
    
  • Apply emboss:
    convolution="-2 -1 0 -1 1 1 0 1 2:-2 -1 0 -1 1 1 0 1 2:-2 -1 0 -1 1 1 0 1 2:-2 -1 0 -1 1 1 0 1 2"
    

9.21 copy

Copy the input source unchanged to the output. This is mainly useful for testing purposes.

9.22 coreimage

Video filtering on GPU using Apple’s CoreImage API on OSX.

Hardware acceleration is based on an OpenGL context. Usually, this means it is processed by video hardware. However, software-based OpenGL implementations exist which means there is no guarantee for hardware processing. It depends on the respective OSX.

There are many filters and image generators provided by Apple that come with a large variety of options. The filter has to be referenced by its name along with its options.

The coreimage filter accepts the following options:

list_filters

List all available filters and generators along with all their respective options as well as possible minimum and maximum values along with the default values.

list_filters=true
filter

Specify all filters by their respective name and options. Use list_filters to determine all valid filter names and options. Numerical options are specified by a float value and are automatically clamped to their respective value range. Vector and color options have to be specified by a list of space separated float values. Character escaping has to be done. A special option name default is available to use default options for a filter.

It is required to specify either default or at least one of the filter options. All omitted options are used with their default values. The syntax of the filter string is as follows:

filter=<NAME>@<OPTION>=<VALUE>[@<OPTION>=<VALUE>][@...][#<NAME>@<OPTION>=<VALUE>[@<OPTION>=<VALUE>][@...]][#...]
output_rect

Specify a rectangle where the output of the filter chain is copied into the input image. It is given by a list of space separated float values:

output_rect=x\ y\ width\ height

If not given, the output rectangle equals the dimensions of the input image. The output rectangle is automatically cropped at the borders of the input image. Negative values are valid for each component.

output_rect=25\ 25\ 100\ 100

Several filters can be chained for successive processing without GPU-HOST transfers allowing for fast processing of complex filter chains. Currently, only filters with zero (generators) or exactly one (filters) input image and one output image are supported. Also, transition filters are not yet usable as intended.

Some filters generate output images with additional padding depending on the respective filter kernel. The padding is automatically removed to ensure the filter output has the same size as the input image.

For image generators, the size of the output image is determined by the previous output image of the filter chain or the input image of the whole filterchain, respectively. The generators do not use the pixel information of this image to generate their output. However, the generated output is blended onto this image, resulting in partial or complete coverage of the output image.

The coreimagesrc video source can be used for generating input images which are directly fed into the filter chain. By using it, providing input images by another video source or an input video is not required.

9.22.1 Examples

  • List all filters available:
    coreimage=list_filters=true
    
  • Use the CIBoxBlur filter with default options to blur an image:
    coreimage=filter=CIBoxBlur@default
    
  • Use a filter chain with CISepiaTone at default values and CIVignetteEffect with its center at 100x100 and a radius of 50 pixels:
    coreimage=filter=CIBoxBlur@default#CIVignetteEffect@inputCenter=100\ 100@inputRadius=50
    
  • Use nullsrc and CIQRCodeGenerator to create a QR code for the FFmpeg homepage, given as complete and escaped command-line for Apple’s standard bash shell:
    ffmpeg -f lavfi -i nullsrc=s=100x100,coreimage=filter=CIQRCodeGenerator@inputMessage=https\\\\\://FFmpeg.org/@inputCorrectionLevel=H -frames:v 1 QRCode.png
    

9.23 crop

Crop the input video to given dimensions.

It accepts the following parameters:

w, out_w

The width of the output video. It defaults to iw. This expression is evaluated only once during the filter configuration, or when the ‘w’ or ‘out_w’ command is sent.

h, out_h

The height of the output video. It defaults to ih. This expression is evaluated only once during the filter configuration, or when the ‘h’ or ‘out_h’ command is sent.

x

The horizontal position, in the input video, of the left edge of the output video. It defaults to (in_w-out_w)/2. This expression is evaluated per-frame.

y

The vertical position, in the input video, of the top edge of the output video. It defaults to (in_h-out_h)/2. This expression is evaluated per-frame.

keep_aspect

If set to 1 will force the output display aspect ratio to be the same of the input, by changing the output sample aspect ratio. It defaults to 0.

The out_w, out_h, x, y parameters are expressions containing the following constants:

x
y

The computed values for x and y. They are evaluated for each new frame.

in_w
in_h

The input width and height.

iw
ih

These are the same as in_w and in_h.

out_w
out_h

The output (cropped) width and height.

ow
oh

These are the same as out_w and out_h.

a

same as iw / ih

sar

input sample aspect ratio

dar

input display aspect ratio, it is the same as (iw / ih) * sar

hsub
vsub

horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

n

The number of the input frame, starting from 0.

pos

the position in the file of the input frame, NAN if unknown

t

The timestamp expressed in seconds. It’s NAN if the input timestamp is unknown.

The expression for out_w may depend on the value of out_h, and the expression for out_h may depend on out_w, but they cannot depend on x and y, as x and y are evaluated after out_w and out_h.

The x and y parameters specify the expressions for the position of the top-left corner of the output (non-cropped) area. They are evaluated for each frame. If the evaluated value is not valid, it is approximated to the nearest valid value.

The expression for x may depend on y, and the expression for y may depend on x.

9.23.1 Examples

  • Crop area with size 100x100 at position (12,34).
    crop=100:100:12:34
    

    Using named options, the example above becomes:

    crop=w=100:h=100:x=12:y=34
    
  • Crop the central input area with size 100x100:
    crop=100:100
    
  • Crop the central input area with size 2/3 of the input video:
    crop=2/3*in_w:2/3*in_h
    
  • Crop the input video central square:
    crop=out_w=in_h
    crop=in_h
    
  • Delimit the rectangle with the top-left corner placed at position 100:100 and the right-bottom corner corresponding to the right-bottom corner of the input image.
    crop=in_w-100:in_h-100:100:100
    
  • Crop 10 pixels from the left and right borders, and 20 pixels from the top and bottom borders
    crop=in_w-2*10:in_h-2*20
    
  • Keep only the bottom right quarter of the input image:
    crop=in_w/2:in_h/2:in_w/2:in_h/2
    
  • Crop height for getting Greek harmony:
    crop=in_w:1/PHI*in_w
    
  • Apply trembling effect:
    crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)
    
  • Apply erratic camera effect depending on timestamp:
    crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)"
    
  • Set x depending on the value of y:
    crop=in_w/2:in_h/2:y:10+10*sin(n/10)
    

9.23.2 Commands

This filter supports the following commands:

w, out_w
h, out_h
x
y

Set width/height of the output video and the horizontal/vertical position in the input video. The command accepts the same syntax of the corresponding option.

If the specified expression is not valid, it is kept at its current value.

9.24 cropdetect

Auto-detect the crop size.

It calculates the necessary cropping parameters and prints the recommended parameters via the logging system. The detected dimensions correspond to the non-black area of the input video.

It accepts the following parameters:

limit

Set higher black value threshold, which can be optionally specified from nothing (0) to everything (255 for 8-bit based formats). An intensity value greater to the set value is considered non-black. It defaults to 24. You can also specify a value between 0.0 and 1.0 which will be scaled depending on the bitdepth of the pixel format.

round

The value which the width/height should be divisible by. It defaults to 16. The offset is automatically adjusted to center the video. Use 2 to get only even dimensions (needed for 4:2:2 video). 16 is best when encoding to most video codecs.

reset_count, reset

Set the counter that determines after how many frames cropdetect will reset the previously detected largest video area and start over to detect the current optimal crop area. Default value is 0.

This can be useful when channel logos distort the video area. 0 indicates ’never reset’, and returns the largest area encountered during playback.

9.25 curves

Apply color adjustments using curves.

This filter is similar to the Adobe Photoshop and GIMP curves tools. Each component (red, green and blue) has its values defined by N key points tied from each other using a smooth curve. The x-axis represents the pixel values from the input frame, and the y-axis the new pixel values to be set for the output frame.

By default, a component curve is defined by the two points (0;0) and (1;1). This creates a straight line where each original pixel value is "adjusted" to its own value, which means no change to the image.

The filter allows you to redefine these two points and add some more. A new curve (using a natural cubic spline interpolation) will be define to pass smoothly through all these new coordinates. The new defined points needs to be strictly increasing over the x-axis, and their x and y values must be in the [0;1] interval. If the computed curves happened to go outside the vector spaces, the values will be clipped accordingly.

If there is no key point defined in x=0, the filter will automatically insert a (0;0) point. In the same way, if there is no key point defined in x=1, the filter will automatically insert a (1;1) point.

The filter accepts the following options:

preset

Select one of the available color presets. This option can be used in addition to the r, g, b parameters; in this case, the later options takes priority on the preset values. Available presets are:

none
color_negative
cross_process
darker
increase_contrast
lighter
linear_contrast
medium_contrast
negative
strong_contrast
vintage

Default is none.

master, m

Set the master key points. These points will define a second pass mapping. It is sometimes called a "luminance" or "value" mapping. It can be used with r, g, b or all since it acts like a post-processing LUT.

red, r

Set the key points for the red component.

green, g

Set the key points for the green component.

blue, b

Set the key points for the blue component.

all

Set the key points for all components (not including master). Can be used in addition to the other key points component options. In this case, the unset component(s) will fallback on this all setting.

psfile

Specify a Photoshop curves file (.acv) to import the settings from.

To avoid some filtergraph syntax conflicts, each key points list need to be defined using the following syntax: x0/y0 x1/y1 x2/y2 ....

9.25.1 Examples

  • Increase slightly the middle level of blue:
    curves=blue='0.5/0.58'
    
  • Vintage effect:
    curves=r='0/0.11 .42/.51 1/0.95':g='0.50/0.48':b='0/0.22 .49/.44 1/0.8'
    

    Here we obtain the following coordinates for each components:

    red

    (0;0.11) (0.42;0.51) (1;0.95)

    green

    (0;0) (0.50;0.48) (1;1)

    blue

    (0;0.22) (0.49;0.44) (1;0.80)

  • The previous example can also be achieved with the associated built-in preset:
    curves=preset=vintage
    
  • Or simply:
    curves=vintage
    
  • Use a Photoshop preset and redefine the points of the green component:
    curves=psfile='MyCurvesPresets/purple.acv':green='0.45/0.53'
    

9.26 datascope

Video data analysis filter.

This filter shows hexadecimal pixel values of part of video.

The filter accepts the following options:

size, s

Set output video size.

x

Set x offset from where to pick pixels.

y

Set y offset from where to pick pixels.

mode

Set scope mode, can be one of the following:

mono

Draw hexadecimal pixel values with white color on black background.

color

Draw hexadecimal pixel values with input video pixel color on black background.

color2

Draw hexadecimal pixel values on color background picked from input video, the text color is picked in such way so its always visible.

axis

Draw rows and columns numbers on left and top of video.

9.27 dctdnoiz

Denoise frames using 2D DCT (frequency domain filtering).

This filter is not designed for real time.

The filter accepts the following options:

sigma, s

Set the noise sigma constant.

This sigma defines a hard threshold of 3 * sigma; every DCT coefficient (absolute value) below this threshold with be dropped.

If you need a more advanced filtering, see expr.

Default is 0.

overlap

Set number overlapping pixels for each block. Since the filter can be slow, you may want to reduce this value, at the cost of a less effective filter and the risk of various artefacts.

If the overlapping value doesn’t permit processing the whole input width or height, a warning will be displayed and according borders won’t be denoised.

Default value is blocksize-1, which is the best possible setting.

expr, e

Set the coefficient factor expression.

For each coefficient of a DCT block, this expression will be evaluated as a multiplier value for the coefficient.

If this is option is set, the sigma option will be ignored.

The absolute value of the coefficient can be accessed through the c variable.

n

Set the blocksize using the number of bits. 1<<n defines the blocksize, which is the width and height of the processed blocks.

The default value is 3 (8x8) and can be raised to 4 for a blocksize of 16x16. Note that changing this setting has huge consequences on the speed processing. Also, a larger block size does not necessarily means a better de-noising.

9.27.1 Examples

Apply a denoise with a sigma of 4.5:

dctdnoiz=4.5

The same operation can be achieved using the expression system:

dctdnoiz=e='gte(c, 4.5*3)'

Violent denoise using a block size of 16x16:

dctdnoiz=15:n=4

9.28 deband

Remove banding artifacts from input video. It works by replacing banded pixels with average value of referenced pixels.

The filter accepts the following options:

1thr
2thr
3thr
4thr

Set banding detection threshold for each plane. Default is 0.02. Valid range is 0.00003 to 0.5. If difference between current pixel and reference pixel is less than threshold, it will be considered as banded.

range, r

Banding detection range in pixels. Default is 16. If positive, random number in range 0 to set value will be used. If negative, exact absolute value will be used. The range defines square of four pixels around current pixel.

direction, d

Set direction in radians from which four pixel will be compared. If positive, random direction from 0 to set direction will be picked. If negative, exact of absolute value will be picked. For example direction 0, -PI or -2*PI radians will pick only pixels on same row and -PI/2 will pick only pixels on same column.

blur

If enabled, current pixel is compared with average value of all four surrounding pixels. The default is enabled. If disabled current pixel is compared with all four surrounding pixels. The pixel is considered banded if only all four differences with surrounding pixels are less than threshold.

9.29 decimate

Drop duplicated frames at regular intervals.

The filter accepts the following options:

cycle

Set the number of frames from which one will be dropped. Setting this to N means one frame in every batch of N frames will be dropped. Default is 5.

dupthresh

Set the threshold for duplicate detection. If the difference metric for a frame is less than or equal to this value, then it is declared as duplicate. Default is 1.1

scthresh

Set scene change threshold. Default is 15.

blockx
blocky

Set the size of the x and y-axis blocks used during metric calculations. Larger blocks give better noise suppression, but also give worse detection of small movements. Must be a power of two. Default is 32.

ppsrc

Mark main input as a pre-processed input and activate clean source input stream. This allows the input to be pre-processed with various filters to help the metrics calculation while keeping the frame selection lossless. When set to 1, the first stream is for the pre-processed input, and the second stream is the clean source from where the kept frames are chosen. Default is 0.

chroma

Set whether or not chroma is considered in the metric calculations. Default is 1.

9.30 deflate

Apply deflate effect to the video.

This filter replaces the pixel by the local(3x3) average by taking into account only values lower than the pixel.

It accepts the following options:

threshold0
threshold1
threshold2
threshold3

Limit the maximum change for each plane, default is 65535. If 0, plane will remain unchanged.

9.31 dejudder

Remove judder produced by partially interlaced telecined content.

Judder can be introduced, for instance, by pullup filter. If the original source was partially telecined content then the output of pullup,dejudder will have a variable frame rate. May change the recorded frame rate of the container. Aside from that change, this filter will not affect constant frame rate video.

The option available in this filter is:

cycle

Specify the length of the window over which the judder repeats.

Accepts any integer greater than 1. Useful values are:

4

If the original was telecined from 24 to 30 fps (Film to NTSC).

5

If the original was telecined from 25 to 30 fps (PAL to NTSC).

20

If a mixture of the two.

The default is ‘4’.

9.32 delogo

Suppress a TV station logo by a simple interpolation of the surrounding pixels. Just set a rectangle covering the logo and watch it disappear (and sometimes something even uglier appear - your mileage may vary).

It accepts the following parameters:

x
y

Specify the top left corner coordinates of the logo. They must be specified.

w
h

Specify the width and height of the logo to clear. They must be specified.

band, t

Specify the thickness of the fuzzy edge of the rectangle (added to w and h). The default value is 1. This option is deprecated, setting higher values should no longer be necessary and is not recommended.

show

When set to 1, a green rectangle is drawn on the screen to simplify finding the right x, y, w, and h parameters. The default value is 0.

The rectangle is drawn on the outermost pixels which will be (partly) replaced with interpolated values. The values of the next pixels immediately outside this rectangle in each direction will be used to compute the interpolated pixel values inside the rectangle.

9.32.1 Examples

  • Set a rectangle covering the area with top left corner coordinates 0,0 and size 100x77, and a band of size 10:
    delogo=x=0:y=0:w=100:h=77:band=10
    

9.33 deshake

Attempt to fix small changes in horizontal and/or vertical shift. This filter helps remove camera shake from hand-holding a camera, bumping a tripod, moving on a vehicle, etc.

The filter accepts the following options:

x
y
w
h

Specify a rectangular area where to limit the search for motion vectors. If desired the search for motion vectors can be limited to a rectangular area of the frame defined by its top left corner, width and height. These parameters have the same meaning as the drawbox filter which can be used to visualise the position of the bounding box.

This is useful when simultaneous movement of subjects within the frame might be confused for camera motion by the motion vector search.

If any or all of x, y, w and h are set to -1 then the full frame is used. This allows later options to be set without specifying the bounding box for the motion vector search.

Default - search the whole frame.

rx
ry

Specify the maximum extent of movement in x and y directions in the range 0-64 pixels. Default 16.

edge

Specify how to generate pixels to fill blanks at the edge of the frame. Available values are:

blank, 0

Fill zeroes at blank locations

original, 1

Original image at blank locations

clamp, 2

Extruded edge value at blank locations

mirror, 3

Mirrored edge at blank locations

Default value is ‘mirror’.

blocksize

Specify the blocksize to use for motion search. Range 4-128 pixels, default 8.

contrast

Specify the contrast threshold for blocks. Only blocks with more than the specified contrast (difference between darkest and lightest pixels) will be considered. Range 1-255, default 125.

search

Specify the search strategy. Available values are:

exhaustive, 0

Set exhaustive search

less, 1

Set less exhaustive search.

Default value is ‘exhaustive’.

filename

If set then a detailed log of the motion search is written to the specified file.

opencl

If set to 1, specify using OpenCL capabilities, only available if FFmpeg was configured with --enable-opencl. Default value is 0.

9.34 detelecine

Apply an exact inverse of the telecine operation. It requires a predefined pattern specified using the pattern option which must be the same as that passed to the telecine filter.

This filter accepts the following options:

first_field
top, t

top field first

bottom, b

bottom field first The default value is top.

pattern

A string of numbers representing the pulldown pattern you wish to apply. The default value is 23.

start_frame

A number representing position of the first frame with respect to the telecine pattern. This is to be used if the stream is cut. The default value is 0.

9.35 dilation

Apply dilation effect to the video.

This filter replaces the pixel by the local(3x3) maximum.

It accepts the following options:

threshold0
threshold1
threshold2
threshold3

Limit the maximum change for each plane, default is 65535. If 0, plane will remain unchanged.

coordinates

Flag which specifies the pixel to refer to. Default is 255 i.e. all eight pixels are used.

Flags to local 3x3 coordinates maps like this:

1 2 3 4 5 6 7 8

9.36 displace

Displace pixels as indicated by second and third input stream.

It takes three input streams and outputs one stream, the first input is the source, and second and third input are displacement maps.

The second input specifies how much to displace pixels along the x-axis, while the third input specifies how much to displace pixels along the y-axis. If one of displacement map streams terminates, last frame from that displacement map will be used.

Note that once generated, displacements maps can be reused over and over again.

A description of the accepted options follows.

edge

Set displace behavior for pixels that are out of range.

Available values are:

blank

Missing pixels are replaced by black pixels.

smear

Adjacent pixels will spread out to replace missing pixels.

wrap

Out of range pixels are wrapped so they point to pixels of other side.

Default is ‘smear’.

9.36.1 Examples

  • Add ripple effect to rgb input of video size hd720:
    ffmpeg -i INPUT -f lavfi -i nullsrc=s=hd720,lutrgb=128:128:128 -f lavfi -i nullsrc=s=hd720,geq='r=128+30*sin(2*PI*X/400+T):g=128+30*sin(2*PI*X/400+T):b=128+30*sin(2*PI*X/400+T)' -lavfi '[0][1][2]displace' OUTPUT
    
  • Add wave effect to rgb input of video size hd720:
    ffmpeg -i INPUT -f lavfi -i nullsrc=hd720,geq='r=128+80*(sin(sqrt((X-W/2)*(X-W/2)+(Y-H/2)*(Y-H/2))/220*2*PI+T)):g=128+80*(sin(sqrt((X-W/2)*(X-W/2)+(Y-H/2)*(Y-H/2))/220*2*PI+T)):b=128+80*(sin(sqrt((X-W/2)*(X-W/2)+(Y-H/2)*(Y-H/2))/220*2*PI+T))' -lavfi '[1]split[x][y],[0][x][y]displace' OUTPUT
    

9.37 drawbox

Draw a colored box on the input image.

It accepts the following parameters:

x
y

The expressions which specify the top left corner coordinates of the box. It defaults to 0.

width, w
height, h

The expressions which specify the width and height of the box; if 0 they are interpreted as the input width and height. It defaults to 0.

color, c

Specify the color of the box to write. For the general syntax of this option, check the "Color" section in the ffmpeg-utils manual. If the special value invert is used, the box edge color is the same as the video with inverted luma.

thickness, t

The expression which sets the thickness of the box edge. Default value is 3.

See below for the list of accepted constants.

The parameters for x, y, w and h and t are expressions containing the following constants:

dar

The input display aspect ratio, it is the same as (w / h) * sar.

hsub
vsub

horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

in_h, ih
in_w, iw

The input width and height.

sar

The input sample aspect ratio.

x
y

The x and y offset coordinates where the box is drawn.

w
h

The width and height of the drawn box.

t

The thickness of the drawn box.

These constants allow the x, y, w, h and t expressions to refer to each other, so you may for example specify y=x/dar or h=w/dar.

9.37.1 Examples

  • Draw a black box around the edge of the input image:
    drawbox
    
  • Draw a box with color red and an opacity of 50%:
    drawbox=10:20:200:60:red@0.5
    

    The previous example can be specified as:

    drawbox=x=10:y=20:w=200:h=60:color=red@0.5
    
  • Fill the box with pink color:
    drawbox=x=10:y=10:w=100:h=100:color=pink@0.5:t=max
    
  • Draw a 2-pixel red 2.40:1 mask:
    drawbox=x=-t:y=0.5*(ih-iw/2.4)-t:w=iw+t*2:h=iw/2.4+t*2:t=2:c=red
    

9.38 drawgraph, adrawgraph

Draw a graph using input video or audio metadata.

It accepts the following parameters:

m1

Set 1st frame metadata key from which metadata values will be used to draw a graph.

fg1

Set 1st foreground color expression.

m2

Set 2nd frame metadata key from which metadata values will be used to draw a graph.

fg2

Set 2nd foreground color expression.

m3

Set 3rd frame metadata key from which metadata values will be used to draw a graph.

fg3

Set 3rd foreground color expression.

m4

Set 4th frame metadata key from which metadata values will be used to draw a graph.

fg4

Set 4th foreground color expression.

min

Set minimal value of metadata value.

max

Set maximal value of metadata value.

bg

Set graph background color. Default is white.

mode

Set graph mode.

Available values for mode is:

bar
dot
line

Default is line.

slide

Set slide mode.

Available values for slide is:

frame

Draw new frame when right border is reached.

replace

Replace old columns with new ones.

scroll

Scroll from right to left.

rscroll

Scroll from left to right.

Default is frame.

size

Set size of graph video. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual. The default value is 900x256.

The foreground color expressions can use the following variables:

MIN

Minimal value of metadata value.

MAX

Maximal value of metadata value.

VAL

Current metadata key value.

The color is defined as 0xAABBGGRR.

Example using metadata from signalstats filter:

signalstats,drawgraph=lavfi.signalstats.YAVG:min=0:max=255

Example using metadata from ebur128 filter:

ebur128=metadata=1,adrawgraph=lavfi.r128.M:min=-120:max=5

9.39 drawgrid

Draw a grid on the input image.

It accepts the following parameters:

x
y

The expressions which specify the coordinates of some point of grid intersection (meant to configure offset). Both default to 0.

width, w
height, h

The expressions which specify the width and height of the grid cell, if 0 they are interpreted as the input width and height, respectively, minus thickness, so image gets framed. Default to 0.

color, c

Specify the color of the grid. For the general syntax of this option, check the "Color" section in the ffmpeg-utils manual. If the special value invert is used, the grid color is the same as the video with inverted luma.

thickness, t

The expression which sets the thickness of the grid line. Default value is 1.

See below for the list of accepted constants.

The parameters for x, y, w and h and t are expressions containing the following constants:

dar

The input display aspect ratio, it is the same as (w / h) * sar.

hsub
vsub

horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

in_h, ih
in_w, iw

The input grid cell width and height.

sar

The input sample aspect ratio.

x
y

The x and y coordinates of some point of grid intersection (meant to configure offset).

w
h

The width and height of the drawn cell.

t

The thickness of the drawn cell.

These constants allow the x, y, w, h and t expressions to refer to each other, so you may for example specify y=x/dar or h=w/dar.

9.39.1 Examples

  • Draw a grid with cell 100x100 pixels, thickness 2 pixels, with color red and an opacity of 50%:
    drawgrid=width=100:height=100:thickness=2:color=red@0.5
    
  • Draw a white 3x3 grid with an opacity of 50%:
    drawgrid=w=iw/3:h=ih/3:t=2:c=white@0.5
    

9.40 drawtext

Draw a text string or text from a specified file on top of a video, using the libfreetype library.

To enable compilation of this filter, you need to configure FFmpeg with --enable-libfreetype. To enable default font fallback and the font option you need to configure FFmpeg with --enable-libfontconfig. To enable the text_shaping option, you need to configure FFmpeg with --enable-libfribidi.

9.40.1 Syntax

It accepts the following parameters:

box

Used to draw a box around text using the background color. The value must be either 1 (enable) or 0 (disable). The default value of box is 0.

boxborderw

Set the width of the border to be drawn around the box using boxcolor. The default value of boxborderw is 0.

boxcolor

The color to be used for drawing box around text. For the syntax of this option, check the "Color" section in the ffmpeg-utils manual.

The default value of boxcolor is "white".

borderw

Set the width of the border to be drawn around the text using bordercolor. The default value of borderw is 0.

bordercolor

Set the color to be used for drawing border around text. For the syntax of this option, check the "Color" section in the ffmpeg-utils manual.

The default value of bordercolor is "black".

expansion

Select how the text is expanded. Can be either none, strftime (deprecated) or normal (default). See the Text expansion section below for details.

fix_bounds

If true, check and fix text coords to avoid clipping.

fontcolor

The color to be used for drawing fonts. For the syntax of this option, check the "Color" section in the ffmpeg-utils manual.

The default value of fontcolor is "black".

fontcolor_expr

String which is expanded the same way as text to obtain dynamic fontcolor value. By default this option has empty value and is not processed. When this option is set, it overrides fontcolor option.

font

The font family to be used for drawing text. By default Sans.

fontfile

The font file to be used for drawing text. The path must be included. This parameter is mandatory if the fontconfig support is disabled.

draw

This option does not exist, please see the timeline system

alpha

Draw the text applying alpha blending. The value can be either a number between 0.0 and 1.0 The expression accepts the same variables x, y do. The default value is 1. Please see fontcolor_expr

fontsize

The font size to be used for drawing text. The default value of fontsize is 16.

text_shaping

If set to 1, attempt to shape the text (for example, reverse the order of right-to-left text and join Arabic characters) before drawing it. Otherwise, just draw the text exactly as given. By default 1 (if supported).

ft_load_flags

The flags to be used for loading the fonts.

The flags map the corresponding flags supported by libfreetype, and are a combination of the following values:

default
no_scale
no_hinting
render
no_bitmap
vertical_layout
force_autohint
crop_bitmap
pedantic
ignore_global_advance_width
no_recurse
ignore_transform
monochrome
linear_design
no_autohint

Default value is "default".

For more information consult the documentation for the FT_LOAD_* libfreetype flags.

shadowcolor

The color to be used for drawing a shadow behind the drawn text. For the syntax of this option, check the "Color" section in the ffmpeg-utils manual.

The default value of shadowcolor is "black".

shadowx
shadowy

The x and y offsets for the text shadow position with respect to the position of the text. They can be either positive or negative values. The default value for both is "0".

start_number

The starting frame number for the n/frame_num variable. The default value is "0".

tabsize

The size in number of spaces to use for rendering the tab. Default value is 4.

timecode

Set the initial timecode representation in "hh:mm:ss[:;.]ff" format. It can be used with or without text parameter. timecode_rate option must be specified.

timecode_rate, rate, r

Set the timecode frame rate (timecode only).

text

The text string to be drawn. The text must be a sequence of UTF-8 encoded characters. This parameter is mandatory if no file is specified with the parameter textfile.

textfile

A text file containing text to be drawn. The text must be a sequence of UTF-8 encoded characters.

This parameter is mandatory if no text string is specified with the parameter text.

If both text and textfile are specified, an error is thrown.

reload

If set to 1, the textfile will be reloaded before each frame. Be sure to update it atomically, or it may be read partially, or even fail.

x
y

The expressions which specify the offsets where text will be drawn within the video frame. They are relative to the top/left border of the output image.

The default value of x and y is "0".

See below for the list of accepted constants and functions.

The parameters for x and y are expressions containing the following constants and functions:

dar

input display aspect ratio, it is the same as (w / h) * sar

hsub
vsub

horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

line_h, lh

the height of each text line

main_h, h, H

the input height

main_w, w, W

the input width

max_glyph_a, ascent

the maximum distance from the baseline to the highest/upper grid coordinate used to place a glyph outline point, for all the rendered glyphs. It is a positive value, due to the grid’s orientation with the Y axis upwards.

max_glyph_d, descent

the maximum distance from the baseline to the lowest grid coordinate used to place a glyph outline point, for all the rendered glyphs. This is a negative value, due to the grid’s orientation, with the Y axis upwards.

max_glyph_h

maximum glyph height, that is the maximum height for all the glyphs contained in the rendered text, it is equivalent to ascent - descent.

max_glyph_w

maximum glyph width, that is the maximum width for all the glyphs contained in the rendered text

n

the number of input frame, starting from 0

rand(min, max)

return a random number included between min and max

sar

The input sample aspect ratio.

t

timestamp expressed in seconds, NAN if the input timestamp is unknown

text_h, th

the height of the rendered text

text_w, tw

the width of the rendered text

x
y

the x and y offset coordinates where the text is drawn.

These parameters allow the x and y expressions to refer each other, so you can for example specify y=x/dar.

9.40.2 Text expansion

If expansion is set to strftime, the filter recognizes strftime() sequences in the provided text and expands them accordingly. Check the documentation of strftime(). This feature is deprecated.

If expansion is set to none, the text is printed verbatim.

If expansion is set to normal (which is the default), the following expansion mechanism is used.

The backslash character ‘\’, followed by any character, always expands to the second character.

Sequence of the form %{...} are expanded. The text between the braces is a function name, possibly followed by arguments separated by ’:’. If the arguments contain special characters or delimiters (’:’ or ’}’), they should be escaped.

Note that they probably must also be escaped as the value for the text option in the filter argument string and as the filter argument in the filtergraph description, and possibly also for the shell, that makes up to four levels of escaping; using a text file avoids these problems.

The following functions are available:

expr, e

The expression evaluation result.

It must take one argument specifying the expression to be evaluated, which accepts the same constants and functions as the x and y values. Note that not all constants should be used, for example the text size is not known when evaluating the expression, so the constants text_w and text_h will have an undefined value.

expr_int_format, eif

Evaluate the expression’s value and output as formatted integer.

The first argument is the expression to be evaluated, just as for the expr function. The second argument specifies the output format. Allowed values are ‘x’, ‘X’, ‘d’ and ‘u’. They are treated exactly as in the printf function. The third parameter is optional and sets the number of positions taken by the output. It can be used to add padding with zeros from the left.

gmtime

The time at which the filter is running, expressed in UTC. It can accept an argument: a strftime() format string.

localtime

The time at which the filter is running, expressed in the local time zone. It can accept an argument: a strftime() format string.

metadata

Frame metadata. Takes one or two arguments.

The first argument is mandatory and specifies the metadata key.

The second argument is optional and specifies a default value, used when the metadata key is not found or empty.

n, frame_num

The frame number, starting from 0.

pict_type

A 1 character description of the current picture type.

pts

The timestamp of the current frame. It can take up to three arguments.

The first argument is the format of the timestamp; it defaults to flt for seconds as a decimal number with microsecond accuracy; hms stands for a formatted [-]HH:MM:SS.mmm timestamp with millisecond accuracy. gmtime stands for the timestamp of the frame formatted as UTC time; localtime stands for the timestamp of the frame formatted as local time zone time.

The second argument is an offset added to the timestamp.

If the format is set to localtime or gmtime, a third argument may be supplied: a strftime() format string. By default, YYYY-MM-DD HH:MM:SS format will be used.

9.40.3 Examples

  • Draw "Test Text" with font FreeSerif, using the default values for the optional parameters.
    drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
    
  • Draw ’Test Text’ with font FreeSerif of size 24 at position x=100 and y=50 (counting from the top-left corner of the screen), text is yellow with a red box around it. Both the text and the box have an opacity of 20%.
    drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
              x=100: y=50: fontsize=24: fontcolor=yellow@0.2: box=1: boxcolor=red@0.2"
    

    Note that the double quotes are not necessary if spaces are not used within the parameter list.

  • Show the text at the center of the video frame:
    drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h)/2"
    
  • Show the text at a random position, switching to a new position every 30 seconds:
    drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=if(eq(mod(t\,30)\,0)\,rand(0\,(w-text_w))\,x):y=if(eq(mod(t\,30)\,0)\,rand(0\,(h-text_h))\,y)"
    
  • Show a text line sliding from right to left in the last row of the video frame. The file LONG_LINE is assumed to contain a single line with no newlines.
    drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t"
    
  • Show the content of file CREDITS off the bottom of the frame and scroll up.
    drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"
    
  • Draw a single green letter "g", at the center of the input video. The glyph baseline is placed at half screen height.
    drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent"
    
  • Show text for 1 second every 3 seconds:
    drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:enable=lt(mod(t\,3)\,1):text='blink'"
    
  • Use fontconfig to set the font. Note that the colons need to be escaped.
    drawtext='fontfile=Linux Libertine O-40\:style=Semibold:text=FFmpeg'
    
  • Print the date of a real-time encoding (see strftime(3)):
    drawtext='fontfile=FreeSans.ttf:text=%{localtime\:%a %b %d %Y}'
    
  • Show text fading in and out (appearing/disappearing):
    #!/bin/sh
    DS=1.0 # display start
    DE=10.0 # display end
    FID=1.5 # fade in duration
    FOD=5 # fade out duration
    ffplay -f lavfi "color,drawtext=text=TEST:fontsize=50:fontfile=FreeSerif.ttf:fontcolor_expr=ff0000%{eif\\\\: clip(255*(1*between(t\\, $DS + $FID\\, $DE - $FOD) + ((t - $DS)/$FID)*between(t\\, $DS\\, $DS + $FID) + (-(t - $DE)/$FOD)*between(t\\, $DE - $FOD\\, $DE) )\\, 0\\, 255) \\\\: x\\\\: 2 }"
    

For more information about libfreetype, check: http://www.freetype.org/.

For more information about fontconfig, check: http://freedesktop.org/software/fontconfig/fontconfig-user.html.

For more information about libfribidi, check: http://fribidi.org/.

9.41 edgedetect

Detect and draw edges. The filter uses the Canny Edge Detection algorithm.

The filter accepts the following options:

low
high

Set low and high threshold values used by the Canny thresholding algorithm.

The high threshold selects the "strong" edge pixels, which are then connected through 8-connectivity with the "weak" edge pixels selected by the low threshold.

low and high threshold values must be chosen in the range [0,1], and low should be lesser or equal to high.

Default value for low is 20/255, and default value for high is 50/255.

mode

Define the drawing mode.

wires

Draw white/gray wires on black background.

colormix

Mix the colors to create a paint/cartoon effect.

Default value is wires.

9.41.1 Examples

  • Standard edge detection with custom values for the hysteresis thresholding:
    edgedetect=low=0.1:high=0.4
    
  • Painting effect without thresholding:
    edgedetect=mode=colormix:high=0
    

9.42 eq

Set brightness, contrast, saturation and approximate gamma adjustment.

The filter accepts the following options:

contrast

Set the contrast expression. The value must be a float value in range -2.0 to 2.0. The default value is "1".

brightness

Set the brightness expression. The value must be a float value in range -1.0 to 1.0. The default value is "0".

saturation

Set the saturation expression. The value must be a float in range 0.0 to 3.0. The default value is "1".

gamma

Set the gamma expression. The value must be a float in range 0.1 to 10.0. The default value is "1".

gamma_r

Set the gamma expression for red. The value must be a float in range 0.1 to 10.0. The default value is "1".

gamma_g

Set the gamma expression for green. The value must be a float in range 0.1 to 10.0. The default value is "1".

gamma_b

Set the gamma expression for blue. The value must be a float in range 0.1 to 10.0. The default value is "1".

gamma_weight

Set the gamma weight expression. It can be used to reduce the effect of a high gamma value on bright image areas, e.g. keep them from getting overamplified and just plain white. The value must be a float in range 0.0 to 1.0. A value of 0.0 turns the gamma correction all the way down while 1.0 leaves it at its full strength. Default is "1".

eval

Set when the expressions for brightness, contrast, saturation and gamma expressions are evaluated.

It accepts the following values:

init

only evaluate expressions once during the filter initialization or when a command is processed

frame

evaluate expressions for each incoming frame

Default value is ‘init’.

The expressions accept the following parameters:

n

frame count of the input frame starting from 0

pos

byte position of the corresponding packet in the input file, NAN if unspecified

r

frame rate of the input video, NAN if the input frame rate is unknown

t

timestamp expressed in seconds, NAN if the input timestamp is unknown

9.42.1 Commands

The filter supports the following commands:

contrast

Set the contrast expression.

brightness

Set the brightness expression.

saturation

Set the saturation expression.

gamma

Set the gamma expression.

gamma_r

Set the gamma_r expression.

gamma_g

Set gamma_g expression.

gamma_b

Set gamma_b expression.

gamma_weight

Set gamma_weight expression.

The command accepts the same syntax of the corresponding option.

If the specified expression is not valid, it is kept at its current value.

9.43 erosion

Apply erosion effect to the video.

This filter replaces the pixel by the local(3x3) minimum.

It accepts the following options:

threshold0
threshold1
threshold2
threshold3

Limit the maximum change for each plane, default is 65535. If 0, plane will remain unchanged.

coordinates

Flag which specifies the pixel to refer to. Default is 255 i.e. all eight pixels are used.

Flags to local 3x3 coordinates maps like this:

1 2 3 4 5 6 7 8

9.44 extractplanes

Extract color channel components from input video stream into separate grayscale video streams.

The filter accepts the following option:

planes

Set plane(s) to extract.

Available values for planes are:

y
u
v
a
r
g
b

Choosing planes not available in the input will result in an error. That means you cannot select r, g, b planes with y, u, v planes at same time.

9.44.1 Examples

  • Extract luma, u and v color channel component from input video frame into 3 grayscale outputs:
    ffmpeg -i video.avi -filter_complex 'extractplanes=y+u+v[y][u][v]' -map '[y]' y.avi -map '[u]' u.avi -map '[v]' v.avi
    

9.45 elbg

Apply a posterize effect using the ELBG (Enhanced LBG) algorithm.

For each input image, the filter will compute the optimal mapping from the input to the output given the codebook length, that is the number of distinct output colors.

This filter accepts the following options.

codebook_length, l

Set codebook length. The value must be a positive integer, and represents the number of distinct output colors. Default value is 256.

nb_steps, n

Set the maximum number of iterations to apply for computing the optimal mapping. The higher the value the better the result and the higher the computation time. Default value is 1.

seed, s

Set a random seed, must be an integer included between 0 and UINT32_MAX. If not specified, or if explicitly set to -1, the filter will try to use a good random seed on a best effort basis.

pal8

Set pal8 output pixel format. This option does not work with codebook length greater than 256.

9.46 fade

Apply a fade-in/out effect to the input video.

It accepts the following parameters:

type, t

The effect type can be either "in" for a fade-in, or "out" for a fade-out effect. Default is in.

start_frame, s

Specify the number of the frame to start applying the fade effect at. Default is 0.

nb_frames, n

The number of frames that the fade effect lasts. At the end of the fade-in effect, the output video will have the same intensity as the input video. At the end of the fade-out transition, the output video will be filled with the selected color. Default is 25.

alpha

If set to 1, fade only alpha channel, if one exists on the input. Default value is 0.

start_time, st

Specify the timestamp (in seconds) of the frame to start to apply the fade effect. If both start_frame and start_time are specified, the fade will start at whichever comes last. Default is 0.

duration, d

The number of seconds for which the fade effect has to last. At the end of the fade-in effect the output video will have the same intensity as the input video, at the end of the fade-out transition the output video will be filled with the selected color. If both duration and nb_frames are specified, duration is used. Default is 0 (nb_frames is used by default).

color, c

Specify the color of the fade. Default is "black".

9.46.1 Examples

  • Fade in the first 30 frames of video:
    fade=in:0:30
    

    The command above is equivalent to:

    fade=t=in:s=0:n=30
    
  • Fade out the last 45 frames of a 200-frame video:
    fade=out:155:45
    fade=type=out:start_frame=155:nb_frames=45
    
  • Fade in the first 25 frames and fade out the last 25 frames of a 1000-frame video:
    fade=in:0:25, fade=out:975:25
    
  • Make the first 5 frames yellow, then fade in from frame 5-24:
    fade=in:5:20:color=yellow
    
  • Fade in alpha over first 25 frames of video:
    fade=in:0:25:alpha=1
    
  • Make the first 5.5 seconds black, then fade in for 0.5 seconds:
    fade=t=in:st=5.5:d=0.5
    

9.47 fftfilt

Apply arbitrary expressions to samples in frequency domain

dc_Y

Adjust the dc value (gain) of the luma plane of the image. The filter accepts an integer value in range 0 to 1000. The default value is set to 0.

dc_U

Adjust the dc value (gain) of the 1st chroma plane of the image. The filter accepts an integer value in range 0 to 1000. The default value is set to 0.

dc_V

Adjust the dc value (gain) of the 2nd chroma plane of the image. The filter accepts an integer value in range 0 to 1000. The default value is set to 0.

weight_Y

Set the frequency domain weight expression for the luma plane.

weight_U

Set the frequency domain weight expression for the 1st chroma plane.

weight_V

Set the frequency domain weight expression for the 2nd chroma plane.

The filter accepts the following variables:

X
Y

The coordinates of the current sample.

W
H

The width and height of the image.

9.47.1 Examples

  • High-pass:
    fftfilt=dc_Y=128:weight_Y='squish(1-(Y+X)/100)'
    
  • Low-pass:
    fftfilt=dc_Y=0:weight_Y='squish((Y+X)/100-1)'
    
  • Sharpen:
    fftfilt=dc_Y=0:weight_Y='1+squish(1-(Y+X)/100)'
    
  • Blur:
    fftfilt=dc_Y=0:weight_Y='exp(-4 * ((Y+X)/(W+H)))'
    

9.48 field

Extract a single field from an interlaced image using stride arithmetic to avoid wasting CPU time. The output frames are marked as non-interlaced.

The filter accepts the following options:

type

Specify whether to extract the top (if the value is 0 or top) or the bottom field (if the value is 1 or bottom).

9.49 fieldhint

Create new frames by copying the top and bottom fields from surrounding frames supplied as numbers by the hint file.

hint

Set file containing hints: absolute/relative frame numbers.

There must be one line for each frame in a clip. Each line must contain two numbers separated by the comma, optionally followed by - or +. Numbers supplied on each line of file can not be out of [N-1,N+1] where N is current frame number for absolute mode or out of [-1, 1] range for relative mode. First number tells from which frame to pick up top field and second number tells from which frame to pick up bottom field.

If optionally followed by + output frame will be marked as interlaced, else if followed by - output frame will be marked as progressive, else it will be marked same as input frame. If line starts with # or ; that line is skipped.

mode

Can be item absolute or relative. Default is absolute.

Example of first several lines of hint file for relative mode:

0,0 - # first frame
1,0 - # second frame, use third's frame top field and second's frame bottom field
1,0 - # third frame, use fourth's frame top field and third's frame bottom field
1,0 -
0,0 -
0,0 -
1,0 -
1,0 -
1,0 -
0,0 -
0,0 -
1,0 -
1,0 -
1,0 -
0,0 -

9.50 fieldmatch

Field matching filter for inverse telecine. It is meant to reconstruct the progressive frames from a telecined stream. The filter does not drop duplicated frames, so to achieve a complete inverse telecine fieldmatch needs to be followed by a decimation filter such as decimate in the filtergraph.

The separation of the field matching and the decimation is notably motivated by the possibility of inserting a de-interlacing filter fallback between the two. If the source has mixed telecined and real interlaced content, fieldmatch will not be able to match fields for the interlaced parts. But these remaining combed frames will be marked as interlaced, and thus can be de-interlaced by a later filter such as yadif before decimation.

In addition to the various configuration options, fieldmatch can take an optional second stream, activated through the ppsrc option. If enabled, the frames reconstruction will be based on the fields and frames from this second stream. This allows the first input to be pre-processed in order to help the various algorithms of the filter, while keeping the output lossless (assuming the fields are matched properly). Typically, a field-aware denoiser, or brightness/contrast adjustments can help.

Note that this filter uses the same algorithms as TIVTC/TFM (AviSynth project) and VIVTC/VFM (VapourSynth project). The later is a light clone of TFM from which fieldmatch is based on. While the semantic and usage are very close, some behaviour and options names can differ.

The decimate filter currently only works for constant frame rate input. If your input has mixed telecined (30fps) and progressive content with a lower framerate like 24fps use the following filterchain to produce the necessary cfr stream: dejudder,fps=30000/1001,fieldmatch,decimate.

The filter accepts the following options:

order

Specify the assumed field order of the input stream. Available values are:

auto

Auto detect parity (use FFmpeg’s internal parity value).

bff

Assume bottom field first.

tff

Assume top field first.

Note that it is sometimes recommended not to trust the parity announced by the stream.

Default value is auto.

mode

Set the matching mode or strategy to use. pc mode is the safest in the sense that it won’t risk creating jerkiness due to duplicate frames when possible, but if there are bad edits or blended fields it will end up outputting combed frames when a good match might actually exist. On the other hand, pcn_ub mode is the most risky in terms of creating jerkiness, but will almost always find a good frame if there is one. The other values are all somewhere in between pc and pcn_ub in terms of risking jerkiness and creating duplicate frames versus finding good matches in sections with bad edits, orphaned fields, blended fields, etc.

More details about p/c/n/u/b are available in p/c/n/u/b meaning section.

Available values are:

pc

2-way matching (p/c)

pc_n

2-way matching, and trying 3rd match if still combed (p/c + n)

pc_u

2-way matching, and trying 3rd match (same order) if still combed (p/c + u)

pc_n_ub

2-way matching, trying 3rd match if still combed, and trying 4th/5th matches if still combed (p/c + n + u/b)

pcn

3-way matching (p/c/n)

pcn_ub

3-way matching, and trying 4th/5th matches if all 3 of the original matches are detected as combed (p/c/n + u/b)

The parenthesis at the end indicate the matches that would be used for that mode assuming order=tff (and field on auto or top).

In terms of speed pc mode is by far the fastest and pcn_ub is the slowest.

Default value is pc_n.

ppsrc

Mark the main input stream as a pre-processed input, and enable the secondary input stream as the clean source to pick the fields from. See the filter introduction for more details. It is similar to the clip2 feature from VFM/TFM.

Default value is 0 (disabled).

field

Set the field to match from. It is recommended to set this to the same value as order unless you experience matching failures with that setting. In certain circumstances changing the field that is used to match from can have a large impact on matching performance. Available values are:

auto

Automatic (same value as order).

bottom

Match from the bottom field.

top

Match from the top field.

Default value is auto.

mchroma

Set whether or not chroma is included during the match comparisons. In most cases it is recommended to leave this enabled. You should set this to 0 only if your clip has bad chroma problems such as heavy rainbowing or other artifacts. Setting this to 0 could also be used to speed things up at the cost of some accuracy.

Default value is 1.

y0
y1

These define an exclusion band which excludes the lines between y0 and y1 from being included in the field matching decision. An exclusion band can be used to ignore subtitles, a logo, or other things that may interfere with the matching. y0 sets the starting scan line and y1 sets the ending line; all lines in between y0 and y1 (including y0 and y1) will be ignored. Setting y0 and y1 to the same value will disable the feature. y0 and y1 defaults to 0.

scthresh

Set the scene change detection threshold as a percentage of maximum change on the luma plane. Good values are in the [8.0, 14.0] range. Scene change detection is only relevant in case combmatch=sc. The range for scthresh is [0.0, 100.0].

Default value is 12.0.

combmatch

When combatch is not none, fieldmatch will take into account the combed scores of matches when deciding what match to use as the final match. Available values are:

none

No final matching based on combed scores.

sc

Combed scores are only used when a scene change is detected.

full

Use combed scores all the time.

Default is sc.

combdbg

Force fieldmatch to calculate the combed metrics for certain matches and print them. This setting is known as micout in TFM/VFM vocabulary. Available values are:

none

No forced calculation.

pcn

Force p/c/n calculations.

pcnub

Force p/c/n/u/b calculations.

Default value is none.

cthresh

This is the area combing threshold used for combed frame detection. This essentially controls how "strong" or "visible" combing must be to be detected. Larger values mean combing must be more visible and smaller values mean combing can be less visible or strong and still be detected. Valid settings are from -1 (every pixel will be detected as combed) to 255 (no pixel will be detected as combed). This is basically a pixel difference value. A good range is [8, 12].

Default value is 9.

chroma

Sets whether or not chroma is considered in the combed frame decision. Only disable this if your source has chroma problems (rainbowing, etc.) that are causing problems for the combed frame detection with chroma enabled. Actually, using chroma=0 is usually more reliable, except for the case where there is chroma only combing in the source.

Default value is 0.

blockx
blocky

Respectively set the x-axis and y-axis size of the window used during combed frame detection. This has to do with the size of the area in which combpel pixels are required to be detected as combed for a frame to be declared combed. See the combpel parameter description for more info. Possible values are any number that is a power of 2 starting at 4 and going up to 512.

Default value is 16.

combpel

The number of combed pixels inside any of the blocky by blockx size blocks on the frame for the frame to be detected as combed. While cthresh controls how "visible" the combing must be, this setting controls "how much" combing there must be in any localized area (a window defined by the blockx and blocky settings) on the frame. Minimum value is 0 and maximum is blocky x blockx (at which point no frames will ever be detected as combed). This setting is known as MI in TFM/VFM vocabulary.

Default value is 80.

9.50.1 p/c/n/u/b meaning

9.50.1.1 p/c/n

We assume the following telecined stream:

Top fields:     1 2 2 3 4
Bottom fields:  1 2 3 4 4

The numbers correspond to the progressive frame the fields relate to. Here, the first two frames are progressive, the 3rd and 4th are combed, and so on.

When fieldmatch is configured to run a matching from bottom (field=bottom) this is how this input stream get transformed:

Input stream:
                T     1 2 2 3 4
                B     1 2 3 4 4   <-- matching reference

Matches:              c c n n c

Output stream:
                T     1 2 3 4 4
                B     1 2 3 4 4

As a result of the field matching, we can see that some frames get duplicated. To perform a complete inverse telecine, you need to rely on a decimation filter after this operation. See for instance the decimate filter.

The same operation now matching from top fields (field=top) looks like this:

Input stream:
                T     1 2 2 3 4   <-- matching reference
                B     1 2 3 4 4

Matches:              c c p p c

Output stream:
                T     1 2 2 3 4
                B     1 2 2 3 4

In these examples, we can see what p, c and n mean; basically, they refer to the frame and field of the opposite parity:

  • p matches the field of the opposite parity in the previous frame
  • c matches the field of the opposite parity in the current frame
  • n matches the field of the opposite parity in the next frame

9.50.1.2 u/b

The u and b matching are a bit special in the sense that they match from the opposite parity flag. In the following examples, we assume that we are currently matching the 2nd frame (Top:2, bottom:2). According to the match, a ’x’ is placed above and below each matched fields.

With bottom matching (field=bottom):

Match:           c         p           n          b          u

                 x       x               x        x          x
  Top          1 2 2     1 2 2       1 2 2      1 2 2      1 2 2
  Bottom       1 2 3     1 2 3       1 2 3      1 2 3      1 2 3
                 x         x           x        x              x

Output frames:
                 2          1          2          2          2
                 2          2          2          1          3

With top matching (field=top):

Match:           c         p           n          b          u

                 x         x           x        x              x
  Top          1 2 2     1 2 2       1 2 2      1 2 2      1 2 2
  Bottom       1 2 3     1 2 3       1 2 3      1 2 3      1 2 3
                 x       x               x        x          x

Output frames:
                 2          2          2          1          2
                 2          1          3          2          2

9.50.2 Examples

Simple IVTC of a top field first telecined stream:

fieldmatch=order=tff:combmatch=none, decimate

Advanced IVTC, with fallback on yadif for still combed frames:

fieldmatch=order=tff:combmatch=full, yadif=deint=interlaced, decimate

9.51 fieldorder

Transform the field order of the input video.

It accepts the following parameters:

order

The output field order. Valid values are tff for top field first or bff for bottom field first.

The default value is ‘tff’.

The transformation is done by shifting the picture content up or down by one line, and filling the remaining line with appropriate picture content. This method is consistent with most broadcast field order converters.

If the input video is not flagged as being interlaced, or it is already flagged as being of the required output field order, then this filter does not alter the incoming video.

It is very useful when converting to or from PAL DV material, which is bottom field first.

For example:

ffmpeg -i in.vob -vf "fieldorder=bff" out.dv

9.52 fifo, afifo

Buffer input images and send them when they are requested.

It is mainly useful when auto-inserted by the libavfilter framework.

It does not take parameters.

9.53 find_rect

Find a rectangular object

It accepts the following options:

object

Filepath of the object image, needs to be in gray8.

threshold

Detection threshold, default is 0.5.

mipmaps

Number of mipmaps, default is 3.

xmin, ymin, xmax, ymax

Specifies the rectangle in which to search.

9.53.1 Examples

  • Generate a representative palette of a given video using ffmpeg:
    ffmpeg -i file.ts -vf find_rect=newref.pgm,cover_rect=cover.jpg:mode=cover new.mkv
    

9.54 cover_rect

Cover a rectangular object

It accepts the following options:

cover

Filepath of the optional cover image, needs to be in yuv420.

mode

Set covering mode.

It accepts the following values:

cover

cover it by the supplied image

blur

cover it by interpolating the surrounding pixels

Default value is blur.

9.54.1 Examples

  • Generate a representative palette of a given video using ffmpeg:
    ffmpeg -i file.ts -vf find_rect=newref.pgm,cover_rect=cover.jpg:mode=cover new.mkv
    

9.55 format

Convert the input video to one of the specified pixel formats. Libavfilter will try to pick one that is suitable as input to the next filter.

It accepts the following parameters:

pix_fmts

A ’|’-separated list of pixel format names, such as "pix_fmts=yuv420p|monow|rgb24".

9.55.1 Examples

  • Convert the input video to the yuv420p format
    format=pix_fmts=yuv420p
    

    Convert the input video to any of the formats in the list

    format=pix_fmts=yuv420p|yuv444p|yuv410p
    

9.56 fps

Convert the video to specified constant frame rate by duplicating or dropping frames as necessary.

It accepts the following parameters:

fps

The desired output frame rate. The default is 25.

round

Rounding method.

Possible values are:

zero

zero round towards 0

inf

round away from 0

down

round towards -infinity

up

round towards +infinity

near

round to nearest

The default is near.

start_time

Assume the first PTS should be the given value, in seconds. This allows for padding/trimming at the start of stream. By default, no assumption is made about the first frame’s expected PTS, so no padding or trimming is done. For example, this could be set to 0 to pad the beginning with duplicates of the first frame if a video stream starts after the audio stream or to trim any frames with a negative PTS.

Alternatively, the options can be specified as a flat string: fps[:round].

See also the setpts filter.

9.56.1 Examples

  • A typical usage in order to set the fps to 25:
    fps=fps=25
    
  • Sets the fps to 24, using abbreviation and rounding method to round to nearest:
    fps=fps=film:round=near
    

9.57 framepack

Pack two different video streams into a stereoscopic video, setting proper metadata on supported codecs. The two views should have the same size and framerate and processing will stop when the shorter video ends. Please note that you may conveniently adjust view properties with the scale and fps filters.

It accepts the following parameters:

format

The desired packing format. Supported values are:

sbs

The views are next to each other (default).

tab

The views are on top of each other.

lines

The views are packed by line.

columns

The views are packed by column.

frameseq

The views are temporally interleaved.

Some examples:

# Convert left and right views into a frame-sequential video
ffmpeg -i LEFT -i RIGHT -filter_complex framepack=frameseq OUTPUT

# Convert views into a side-by-side video with the same output resolution as the input
ffmpeg -i LEFT -i RIGHT -filter_complex [0:v]scale=w=iw/2[left],[1:v]scale=w=iw/2[right],[left][right]framepack=sbs OUTPUT

9.58 framerate

Change the frame rate by interpolating new video output frames from the source frames.

This filter is not designed to function correctly with interlaced media. If you wish to change the frame rate of interlaced media then you are required to deinterlace before this filter and re-interlace after this filter.

A description of the accepted options follows.

fps

Specify the output frames per second. This option can also be specified as a value alone. The default is 50.

interp_start

Specify the start of a range where the output frame will be created as a linear interpolation of two frames. The range is [0-255], the default is 15.

interp_end

Specify the end of a range where the output frame will be created as a linear interpolation of two frames. The range is [0-255], the default is 240.

scene

Specify the level at which a scene change is detected as a value between 0 and 100 to indicate a new scene; a low value reflects a low probability for the current frame to introduce a new scene, while a higher value means the current frame is more likely to be one. The default is 7.

flags

Specify flags influencing the filter process.

Available value for flags is:

scene_change_detect, scd

Enable scene change detection using the value of the option scene. This flag is enabled by default.

9.59 framestep

Select one frame every N-th frame.

This filter accepts the following option:

step

Select frame after every step frames. Allowed values are positive integers higher than 0. Default value is 1.

9.60 frei0r

Apply a frei0r effect to the input video.

To enable the compilation of this filter, you need to install the frei0r header and configure FFmpeg with --enable-frei0r.

It accepts the following parameters:

filter_name

The name of the frei0r effect to load. If the environment variable FREI0R_PATH is defined, the frei0r effect is searched for in each of the directories specified by the colon-separated list in FREIOR_PATH. Otherwise, the standard frei0r paths are searched, in this order: HOME/.frei0r-1/lib/, /usr/local/lib/frei0r-1/, /usr/lib/frei0r-1/.

filter_params

A ’|’-separated list of parameters to pass to the frei0r effect.

A frei0r effect parameter can be a boolean (its value is either "y" or "n"), a double, a color (specified as R/G/B, where R, G, and B are floating point numbers between 0.0 and 1.0, inclusive) or by a color description specified in the "Color" section in the ffmpeg-utils manual), a position (specified as X/Y, where X and Y are floating point numbers) and/or a string.

The number and types of parameters depend on the loaded effect. If an effect parameter is not specified, the default value is set.

9.60.1 Examples

  • Apply the distort0r effect, setting the first two double parameters:
    frei0r=filter_name=distort0r:filter_params=0.5|0.01
    
  • Apply the colordistance effect, taking a color as the first parameter:
    frei0r=colordistance:0.2/0.3/0.4
    frei0r=colordistance:violet
    frei0r=colordistance:0x112233
    
  • Apply the perspective effect, specifying the top left and top right image positions:
    frei0r=perspective:0.2/0.2|0.8/0.2
    

For more information, see http://frei0r.dyne.org

9.61 fspp

Apply fast and simple postprocessing. It is a faster version of spp.

It splits (I)DCT into horizontal/vertical passes. Unlike the simple post- processing filter, one of them is performed once per block, not per pixel. This allows for much higher speed.

The filter accepts the following options:

quality

Set quality. This option defines the number of levels for averaging. It accepts an integer in the range 4-5. Default value is 4.

qp

Force a constant quantization parameter. It accepts an integer in range 0-63. If not set, the filter will use the QP from the video stream (if available).

strength

Set filter strength. It accepts an integer in range -15 to 32. Lower values mean more details but also more artifacts, while higher values make the image smoother but also blurrier. Default value is 0 − PSNR optimal.

use_bframe_qp

Enable the use of the QP from the B-Frames if set to 1. Using this option may cause flicker since the B-Frames have often larger QP. Default is 0 (not enabled).

9.62 geq

The filter accepts the following options:

lum_expr, lum

Set the luminance expression.

cb_expr, cb

Set the chrominance blue expression.

cr_expr, cr

Set the chrominance red expression.

alpha_expr, a

Set the alpha expression.

red_expr, r

Set the red expression.

green_expr, g

Set the green expression.

blue_expr, b

Set the blue expression.

The colorspace is selected according to the specified options. If one of the lum_expr, cb_expr, or cr_expr options is specified, the filter will automatically select a YCbCr colorspace. If one of the red_expr, green_expr, or blue_expr options is specified, it will select an RGB colorspace.

If one of the chrominance expression is not defined, it falls back on the other one. If no alpha expression is specified it will evaluate to opaque value. If none of chrominance expressions are specified, they will evaluate to the luminance expression.

The expressions can use the following variables and functions:

N

The sequential number of the filtered frame, starting from 0.

X
Y

The coordinates of the current sample.

W
H

The width and height of the image.

SW
SH

Width and height scale depending on the currently filtered plane. It is the ratio between the corresponding luma plane number of pixels and the current plane ones. E.g. for YUV4:2:0 the values are 1,1 for the luma plane, and 0.5,0.5 for chroma planes.

T

Time of the current frame, expressed in seconds.

p(x, y)

Return the value of the pixel at location (x,y) of the current plane.

lum(x, y)

Return the value of the pixel at location (x,y) of the luminance plane.

cb(x, y)

Return the value of the pixel at location (x,y) of the blue-difference chroma plane. Return 0 if there is no such plane.

cr(x, y)

Return the value of the pixel at location (x,y) of the red-difference chroma plane. Return 0 if there is no such plane.

r(x, y)
g(x, y)
b(x, y)

Return the value of the pixel at location (x,y) of the red/green/blue component. Return 0 if there is no such component.

alpha(x, y)

Return the value of the pixel at location (x,y) of the alpha plane. Return 0 if there is no such plane.

For functions, if x and y are outside the area, the value will be automatically clipped to the closer edge.

9.62.1 Examples

  • Flip the image horizontally:
    geq=p(W-X\,Y)
    
  • Generate a bidimensional sine wave, with angle PI/3 and a wavelength of 100 pixels:
    geq=128 + 100*sin(2*(PI/100)*(cos(PI/3)*(X-50*T) + sin(PI/3)*Y)):128:128
    
  • Generate a fancy enigmatic moving light:
    nullsrc=s=256x256,geq=random(1)/hypot(X-cos(N*0.07)*W/2-W/2\,Y-sin(N*0.09)*H/2-H/2)^2*1000000*sin(N*0.02):128:128
    
  • Generate a quick emboss effect:
    format=gray,geq=lum_expr='(p(X,Y)+(256-p(X-4,Y-4)))/2'
    
  • Modify RGB components depending on pixel position:
    geq=r='X/W*r(X,Y)':g='(1-X/W)*g(X,Y)':b='(H-Y)/H*b(X,Y)'
    
  • Create a radial gradient that is the same size as the input (also see the vignette filter):
    geq=lum=255*gauss((X/W-0.5)*3)*gauss((Y/H-0.5)*3)/gauss(0)/gauss(0),format=gray
    

9.63 gradfun

Fix the banding artifacts that are sometimes introduced into nearly flat regions by truncation to 8-bit color depth. Interpolate the gradients that should go where the bands are, and dither them.

It is designed for playback only. Do not use it prior to lossy compression, because compression tends to lose the dither and bring back the bands.

It accepts the following parameters:

strength

The maximum amount by which the filter will change any one pixel. This is also the threshold for detecting nearly flat regions. Acceptable values range from .51 to 64; the default value is 1.2. Out-of-range values will be clipped to the valid range.

radius

The neighborhood to fit the gradient to. A larger radius makes for smoother gradients, but also prevents the filter from modifying the pixels near detailed regions. Acceptable values are 8-32; the default value is 16. Out-of-range values will be clipped to the valid range.

Alternatively, the options can be specified as a flat string: strength[:radius]

9.63.1 Examples

  • Apply the filter with a 3.5 strength and radius of 8:
    gradfun=3.5:8
    
  • Specify radius, omitting the strength (which will fall-back to the default value):
    gradfun=radius=8
    

9.64 haldclut

Apply a Hald CLUT to a video stream.

First input is the video stream to process, and second one is the Hald CLUT. The Hald CLUT input can be a simple picture or a complete video stream.

The filter accepts the following options:

shortest

Force termination when the shortest input terminates. Default is 0.

repeatlast

Continue applying the last CLUT after the end of the stream. A value of 0 disable the filter after the last frame of the CLUT is reached. Default is 1.

haldclut also has the same interpolation options as lut3d (both filters share the same internals).

More information about the Hald CLUT can be found on Eskil Steenberg’s website (Hald CLUT author) at http://www.quelsolaar.com/technology/clut.html.

9.64.1 Workflow examples

9.64.1.1 Hald CLUT video stream

Generate an identity Hald CLUT stream altered with various effects:

ffmpeg -f lavfi -i haldclutsrc=8 -vf "hue=H=2*PI*t:s=sin(2*PI*t)+1, curves=cross_process" -t 10 -c:v ffv1 clut.nut

Note: make sure you use a lossless codec.

Then use it with haldclut to apply it on some random stream:

ffmpeg -f lavfi -i mandelbrot -i clut.nut -filter_complex '[0][1] haldclut' -t 20 mandelclut.mkv

The Hald CLUT will be applied to the 10 first seconds (duration of clut.nut), then the latest picture of that CLUT stream will be applied to the remaining frames of the mandelbrot stream.

9.64.1.2 Hald CLUT with preview

A Hald CLUT is supposed to be a squared image of Level*Level*Level by Level*Level*Level pixels. For a given Hald CLUT, FFmpeg will select the biggest possible square starting at the top left of the picture. The remaining padding pixels (bottom or right) will be ignored. This area can be used to add a preview of the Hald CLUT.

Typically, the following generated Hald CLUT will be supported by the haldclut filter:

ffmpeg -f lavfi -i haldclutsrc=8 -vf "
   pad=iw+320 [padded_clut];
   smptebars=s=320x256, split [a][b];
   [padded_clut][a] overlay=W-320:h, curves=color_negative [main];
   [main][b] overlay=W-320" -frames:v 1 clut.png

It contains the original and a preview of the effect of the CLUT: SMPTE color bars are displayed on the right-top, and below the same color bars processed by the color changes.

Then, the effect of this Hald CLUT can be visualized with:

ffplay input.mkv -vf "movie=clut.png, [in] haldclut"

9.65 hdcd

Decodes high definition audio cd data. 16-Bit PCM stream containing hdcd flags is converted to 20-bit PCM stream.

9.66 hflip

Flip the input video horizontally.

For example, to horizontally flip the input video with ffmpeg:

ffmpeg -i in.avi -vf "hflip" out.avi

9.67 histeq

This filter applies a global color histogram equalization on a per-frame basis.

It can be used to correct video that has a compressed range of pixel intensities. The filter redistributes the pixel intensities to equalize their distribution across the intensity range. It may be viewed as an "automatically adjusting contrast filter". This filter is useful only for correcting degraded or poorly captured source video.

The filter accepts the following options:

strength

Determine the amount of equalization to be applied. As the strength is reduced, the distribution of pixel intensities more-and-more approaches that of the input frame. The value must be a float number in the range [0,1] and defaults to 0.200.

intensity

Set the maximum intensity that can generated and scale the output values appropriately. The strength should be set as desired and then the intensity can be limited if needed to avoid washing-out. The value must be a float number in the range [0,1] and defaults to 0.210.

antibanding

Set the antibanding level. If enabled the filter will randomly vary the luminance of output pixels by a small amount to avoid banding of the histogram. Possible values are none, weak or strong. It defaults to none.

9.68 histogram

Compute and draw a color distribution histogram for the input video.

The computed histogram is a representation of the color component distribution in an image.

Standard histogram displays the color components distribution in an image. Displays color graph for each color component. Shows distribution of the Y, U, V, A or R, G, B components, depending on input format, in the current frame. Below each graph a color component scale meter is shown.

The filter accepts the following options:

level_height

Set height of level. Default value is 200. Allowed range is [50, 2048].

scale_height

Set height of color scale. Default value is 12. Allowed range is [0, 40].

display_mode

Set display mode. It accepts the following values:

parade

Per color component graphs are placed below each other.

overlay

Presents information identical to that in the parade, except that the graphs representing color components are superimposed directly over one another.

Default is parade.

levels_mode

Set mode. Can be either linear, or logarithmic. Default is linear.

components

Set what color components to display. Default is 7.

9.68.1 Examples

  • Calculate and draw histogram:
    ffplay -i input -vf histogram
    

9.69 hqdn3d

This is a high precision/quality 3d denoise filter. It aims to reduce image noise, producing smooth images and making still images really still. It should enhance compressibility.

It accepts the following optional parameters:

luma_spatial

A non-negative floating point number which specifies spatial luma strength. It defaults to 4.0.

chroma_spatial

A non-negative floating point number which specifies spatial chroma strength. It defaults to 3.0*luma_spatial/4.0.

luma_tmp

A floating point number which specifies luma temporal strength. It defaults to 6.0*luma_spatial/4.0.

chroma_tmp

A floating point number which specifies chroma temporal strength. It defaults to luma_tmp*chroma_spatial/luma_spatial.

9.70 hwupload_cuda

Upload system memory frames to a CUDA device.

It accepts the following optional parameters:

device

The number of the CUDA device to use

9.71 hqx

Apply a high-quality magnification filter designed for pixel art. This filter was originally created by Maxim Stepin.

It accepts the following option:

n

Set the scaling dimension: 2 for hq2x, 3 for hq3x and 4 for hq4x. Default is 3.

9.72 hstack

Stack input videos horizontally.

All streams must be of same pixel format and of same height.

Note that this filter is faster than using overlay and pad filter to create same output.

The filter accept the following option:

inputs

Set number of input streams. Default is 2.

shortest

If set to 1, force the output to terminate when the shortest input terminates. Default value is 0.

9.73 hue

Modify the hue and/or the saturation of the input.

It accepts the following parameters:

h

Specify the hue angle as a number of degrees. It accepts an expression, and defaults to "0".

s

Specify the saturation in the [-10,10] range. It accepts an expression and defaults to "1".

H

Specify the hue angle as a number of radians. It accepts an expression, and defaults to "0".

b

Specify the brightness in the [-10,10] range. It accepts an expression and defaults to "0".

h and H are mutually exclusive, and can’t be specified at the same time.

The b, h, H and s option values are expressions containing the following constants:

n

frame count of the input frame starting from 0

pts

presentation timestamp of the input frame expressed in time base units

r

frame rate of the input video, NAN if the input frame rate is unknown

t

timestamp expressed in seconds, NAN if the input timestamp is unknown

tb

time base of the input video

9.73.1 Examples

  • Set the hue to 90 degrees and the saturation to 1.0:
    hue=h=90:s=1
    
  • Same command but expressing the hue in radians:
    hue=H=PI/2:s=1
    
  • Rotate hue and make the saturation swing between 0 and 2 over a period of 1 second:
    hue="H=2*PI*t: s=sin(2*PI*t)+1"
    
  • Apply a 3 seconds saturation fade-in effect starting at 0:
    hue="s=min(t/3\,1)"
    

    The general fade-in expression can be written as:

    hue="s=min(0\, max((t-START)/DURATION\, 1))"
    
  • Apply a 3 seconds saturation fade-out effect starting at 5 seconds:
    hue="s=max(0\, min(1\, (8-t)/3))"
    

    The general fade-out expression can be written as:

    hue="s=max(0\, min(1\, (START+DURATION-t)/DURATION))"
    

9.73.2 Commands

This filter supports the following commands:

b
s
h
H

Modify the hue and/or the saturation and/or brightness of the input video. The command accepts the same syntax of the corresponding option.

If the specified expression is not valid, it is kept at its current value.

9.74 idet

Detect video interlacing type.

This filter tries to detect if the input frames as interlaced, progressive, top or bottom field first. It will also try and detect fields that are repeated between adjacent frames (a sign of telecine).

Single frame detection considers only immediately adjacent frames when classifying each frame. Multiple frame detection incorporates the classification history of previous frames.

The filter will log these metadata values:

single.current_frame

Detected type of current frame using single-frame detection. One of: “tff” (top field first), “bff” (bottom field first), “progressive”, or “undetermined”

single.tff

Cumulative number of frames detected as top field first using single-frame detection.

multiple.tff

Cumulative number of frames detected as top field first using multiple-frame detection.

single.bff

Cumulative number of frames detected as bottom field first using single-frame detection.

multiple.current_frame

Detected type of current frame using multiple-frame detection. One of: “tff” (top field first), “bff” (bottom field first), “progressive”, or “undetermined”

multiple.bff

Cumulative number of frames detected as bottom field first using multiple-frame detection.

single.progressive

Cumulative number of frames detected as progressive using single-frame detection.

multiple.progressive

Cumulative number of frames detected as progressive using multiple-frame detection.

single.undetermined

Cumulative number of frames that could not be classified using single-frame detection.

multiple.undetermined

Cumulative number of frames that could not be classified using multiple-frame detection.

repeated.current_frame

Which field in the current frame is repeated from the last. One of “neither”, “top”, or “bottom”.

repeated.neither

Cumulative number of frames with no repeated field.

repeated.top

Cumulative number of frames with the top field repeated from the previous frame’s top field.

repeated.bottom

Cumulative number of frames with the bottom field repeated from the previous frame’s bottom field.

The filter accepts the following options:

intl_thres

Set interlacing threshold.

prog_thres

Set progressive threshold.

rep_thres

Threshold for repeated field detection.

half_life

Number of frames after which a given frame’s contribution to the statistics is halved (i.e., it contributes only 0.5 to it’s classification). The default of 0 means that all frames seen are given full weight of 1.0 forever.

analyze_interlaced_flag

When this is not 0 then idet will use the specified number of frames to determine if the interlaced flag is accurate, it will not count undetermined frames. If the flag is found to be accurate it will be used without any further computations, if it is found to be inaccurate it will be cleared without any further computations. This allows inserting the idet filter as a low computational method to clean up the interlaced flag

9.75 il

Deinterleave or interleave fields.

This filter allows one to process interlaced images fields without deinterlacing them. Deinterleaving splits the input frame into 2 fields (so called half pictures). Odd lines are moved to the top half of the output image, even lines to the bottom half. You can process (filter) them independently and then re-interleave them.

The filter accepts the following options:

luma_mode, l
chroma_mode, c
alpha_mode, a

Available values for luma_mode, chroma_mode and alpha_mode are:

none

Do nothing.

deinterleave, d

Deinterleave fields, placing one above the other.

interleave, i

Interleave fields. Reverse the effect of deinterleaving.

Default value is none.

luma_swap, ls
chroma_swap, cs
alpha_swap, as

Swap luma/chroma/alpha fields. Exchange even & odd lines. Default value is 0.

9.76 inflate

Apply inflate effect to the video.

This filter replaces the pixel by the local(3x3) average by taking into account only values higher than the pixel.

It accepts the following options:

threshold0
threshold1
threshold2
threshold3

Limit the maximum change for each plane, default is 65535. If 0, plane will remain unchanged.

9.77 interlace

Simple interlacing filter from progressive contents. This interleaves upper (or lower) lines from odd frames with lower (or upper) lines from even frames, halving the frame rate and preserving image height.

   Original        Original             New Frame
   Frame 'j'      Frame 'j+1'             (tff)
  ==========      ===========       ==================
    Line 0  -------------------->    Frame 'j' Line 0
    Line 1          Line 1  ---->   Frame 'j+1' Line 1
    Line 2 --------------------->    Frame 'j' Line 2
    Line 3          Line 3  ---->   Frame 'j+1' Line 3
     ...             ...                   ...
New Frame + 1 will be generated by Frame 'j+2' and Frame 'j+3' and so on

It accepts the following optional parameters:

scan

This determines whether the interlaced frame is taken from the even (tff - default) or odd (bff) lines of the progressive frame.

lowpass

Enable (default) or disable the vertical lowpass filter to avoid twitter interlacing and reduce moire patterns.

9.78 kerndeint

Deinterlace input video by applying Donald Graft’s adaptive kernel deinterling. Work on interlaced parts of a video to produce progressive frames.

The description of the accepted parameters follows.

thresh

Set the threshold which affects the filter’s tolerance when determining if a pixel line must be processed. It must be an integer in the range [0,255] and defaults to 10. A value of 0 will result in applying the process on every pixels.

map

Paint pixels exceeding the threshold value to white if set to 1. Default is 0.

order

Set the fields order. Swap fields if set to 1, leave fields alone if 0. Default is 0.

sharp

Enable additional sharpening if set to 1. Default is 0.

twoway

Enable twoway sharpening if set to 1. Default is 0.

9.78.1 Examples

  • Apply default values:
    kerndeint=thresh=10:map=0:order=0:sharp=0:twoway=0
    
  • Enable additional sharpening:
    kerndeint=sharp=1
    
  • Paint processed pixels in white:
    kerndeint=map=1
    

9.79 lenscorrection

Correct radial lens distortion

This filter can be used to correct for radial distortion as can result from the use of wide angle lenses, and thereby re-rectify the image. To find the right parameters one can use tools available for example as part of opencv or simply trial-and-error. To use opencv use the calibration sample (under samples/cpp) from the opencv sources and extract the k1 and k2 coefficients from the resulting matrix.

Note that effectively the same filter is available in the open-source tools Krita and Digikam from the KDE project.

In contrast to the vignette filter, which can also be used to compensate lens errors, this filter corrects the distortion of the image, whereas vignette corrects the brightness distribution, so you may want to use both filters together in certain cases, though you will have to take care of ordering, i.e. whether vignetting should be applied before or after lens correction.

9.79.1 Options

The filter accepts the following options:

cx

Relative x-coordinate of the focal point of the image, and thereby the center of the distortion. This value has a range [0,1] and is expressed as fractions of the image width.

cy

Relative y-coordinate of the focal point of the image, and thereby the center of the distortion. This value has a range [0,1] and is expressed as fractions of the image height.

k1

Coefficient of the quadratic correction term. 0.5 means no correction.

k2

Coefficient of the double quadratic correction term. 0.5 means no correction.

The formula that generates the correction is:

r_src = r_tgt * (1 + k1 * (r_tgt / r_0)^2 + k2 * (r_tgt / r_0)^4)

where r_0 is halve of the image diagonal and r_src and r_tgt are the distances from the focal point in the source and target images, respectively.

9.80 loop, aloop

Loop video frames or audio samples.

Those filters accepts the following options:

loop

Set the number of loops.

size

Set maximal size in number of frames for loop filter or maximal number of samples in case of aloop filter.

start

Set first frame of loop for loop filter or first sample of loop in case of aloop filter.

9.81 lut3d

Apply a 3D LUT to an input video.

The filter accepts the following options:

file

Set the 3D LUT file name.

Currently supported formats:

3dl

AfterEffects

cube

Iridas

dat

DaVinci

m3d

Pandora

interp

Select interpolation mode.

Available values are:

nearest

Use values from the nearest defined point.

trilinear

Interpolate values using the 8 points defining a cube.

tetrahedral

Interpolate values using a tetrahedron.

9.82 lut, lutrgb, lutyuv

Compute a look-up table for binding each pixel component input value to an output value, and apply it to the input video.

lutyuv applies a lookup table to a YUV input video, lutrgb to an RGB input video.

These filters accept the following parameters:

c0

set first pixel component expression

c1

set second pixel component expression

c2

set third pixel component expression

c3

set fourth pixel component expression, corresponds to the alpha component

r

set red component expression

g

set green component expression

b

set blue component expression

a

alpha component expression

y

set Y/luminance component expression

u

set U/Cb component expression

v

set V/Cr component expression

Each of them specifies the expression to use for computing the lookup table for the corresponding pixel component values.

The exact component associated to each of the c* options depends on the format in input.

The lut filter requires either YUV or RGB pixel formats in input, lutrgb requires RGB pixel formats in input, and lutyuv requires YUV.

The expressions can contain the following constants and functions:

w
h

The input width and height.

val

The input value for the pixel component.

clipval

The input value, clipped to the minval-maxval range.

maxval

The maximum value for the pixel component.

minval

The minimum value for the pixel component.

negval

The negated value for the pixel component value, clipped to the minval-maxval range; it corresponds to the expression "maxval-clipval+minval".

clip(val)

The computed value in val, clipped to the minval-maxval range.

gammaval(gamma)

The computed gamma correction value of the pixel component value, clipped to the minval-maxval range. It corresponds to the expression "pow((clipval-minval)/(maxval-minval)\,gamma)*(maxval-minval)+minval"

All expressions default to "val".

9.82.1 Examples

  • Negate input video:
    lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
    lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"
    

    The above is the same as:

    lutrgb="r=negval:g=negval:b=negval"
    lutyuv="y=negval:u=negval:v=negval"
    
  • Negate luminance:
    lutyuv=y=negval
    
  • Remove chroma components, turning the video into a graytone image:
    lutyuv="u=128:v=128"
    
  • Apply a luma burning effect:
    lutyuv="y=2*val"
    
  • Remove green and blue components:
    lutrgb="g=0:b=0"
    
  • Set a constant alpha channel value on input:
    format=rgba,lutrgb=a="maxval-minval/2"
    
  • Correct luminance gamma by a factor of 0.5:
    lutyuv=y=gammaval(0.5)
    
  • Discard least significant bits of luma:
    lutyuv=y='bitand(val, 128+64+32)'
    

9.83 maskedmerge

Merge the first input stream with the second input stream using per pixel weights in the third input stream.

A value of 0 in the third stream pixel component means that pixel component from first stream is returned unchanged, while maximum value (eg. 255 for 8-bit videos) means that pixel component from second stream is returned unchanged. Intermediate values define the amount of merging between both input stream’s pixel components.

This filter accepts the following options:

planes

Set which planes will be processed as bitmap, unprocessed planes will be copied from first stream. By default value 0xf, all planes will be processed.

9.84 mcdeint

Apply motion-compensation deinterlacing.

It needs one field per frame as input and must thus be used together with yadif=1/3 or equivalent.

This filter accepts the following options:

mode

Set the deinterlacing mode.

It accepts one of the following values:

fast
medium
slow

use iterative motion estimation

extra_slow

like ‘slow’, but use multiple reference frames.

Default value is ‘fast’.

parity

Set the picture field parity assumed for the input video. It must be one of the following values:

0, tff

assume top field first

1, bff

assume bottom field first

Default value is ‘bff’.

qp

Set per-block quantization parameter (QP) used by the internal encoder.

Higher values should result in a smoother motion vector field but less optimal individual vectors. Default value is 1.

9.85 mergeplanes

Merge color channel components from several video streams.

The filter accepts up to 4 input streams, and merge selected input planes to the output video.

This filter accepts the following options:

mapping

Set input to output plane mapping. Default is 0.

The mappings is specified as a bitmap. It should be specified as a hexadecimal number in the form 0xAa[Bb[Cc[Dd]]]. ’Aa’ describes the mapping for the first plane of the output stream. ’A’ sets the number of the input stream to use (from 0 to 3), and ’a’ the plane number of the corresponding input to use (from 0 to 3). The rest of the mappings is similar, ’Bb’ describes the mapping for the output stream second plane, ’Cc’ describes the mapping for the output stream third plane and ’Dd’ describes the mapping for the output stream fourth plane.

format

Set output pixel format. Default is yuva444p.

9.85.1 Examples

  • Merge three gray video streams of same width and height into single video stream:
    [a0][a1][a2]mergeplanes=0x001020:yuv444p
    
  • Merge 1st yuv444p stream and 2nd gray video stream into yuva444p video stream:
    [a0][a1]mergeplanes=0x00010210:yuva444p
    
  • Swap Y and A plane in yuva444p stream:
    format=yuva444p,mergeplanes=0x03010200:yuva444p
    
  • Swap U and V plane in yuv420p stream:
    format=yuv420p,mergeplanes=0x000201:yuv420p
    
  • Cast a rgb24 clip to yuv444p:
    format=rgb24,mergeplanes=0x000102:yuv444p
    

9.86 metadata, ametadata

Manipulate frame metadata.

This filter accepts the following options:

mode

Set mode of operation of the filter.

Can be one of the following:

select

If both value and key is set, select frames which have such metadata. If only key is set, select every frame that has such key in metadata.

add

Add new metadata key and value. If key is already available do nothing.

modify

Modify value of already present key.

delete

If value is set, delete only keys that have such value. Otherwise, delete key.

print

Print key and its value if metadata was found. If key is not set print all metadata values available in frame.

key

Set key used with all modes. Must be set for all modes except print.

value

Set metadata value which will be used. This option is mandatory for modify and add mode.

function

Which function to use when comparing metadata value and value.

Can be one of following:

same_str

Values are interpreted as strings, returns true if metadata value is same as value.

starts_with

Values are interpreted as strings, returns true if metadata value starts with the value option string.

less

Values are interpreted as floats, returns true if metadata value is less than value.

equal

Values are interpreted as floats, returns true if value is equal with metadata value.

greater

Values are interpreted as floats, returns true if metadata value is greater than value.

expr

Values are interpreted as floats, returns true if expression from option expr evaluates to true.

expr

Set expression which is used when function is set to expr. The expression is evaluated through the eval API and can contain the following constants:

VALUE1

Float representation of value from metadata key.

VALUE2

Float representation of value as supplied by user in value option.

file

If specified in print mode, output is written to the named file. When filename equals "-" data is written to standard output. If file option is not set, output is written to the log with AV_LOG_INFO loglevel.

9.86.1 Examples

  • Print all metadata values for frames with key lavfi.singnalstats.YDIF with values between 0 and 1.

    signalstats,metadata=print:key=lavfi.signalstats.YDIF:value=0:function=expr:expr=’between(VALUE1,0,1)’

9.87 mpdecimate

Drop frames that do not differ greatly from the previous frame in order to reduce frame rate.

The main use of this filter is for very-low-bitrate encoding (e.g. streaming over dialup modem), but it could in theory be used for fixing movies that were inverse-telecined incorrectly.

A description of the accepted options follows.

max

Set the maximum number of consecutive frames which can be dropped (if positive), or the minimum interval between dropped frames (if negative). If the value is 0, the frame is dropped unregarding the number of previous sequentially dropped frames.

Default value is 0.

hi
lo
frac

Set the dropping threshold values.

Values for hi and lo are for 8x8 pixel blocks and represent actual pixel value differences, so a threshold of 64 corresponds to 1 unit of difference for each pixel, or the same spread out differently over the block.

A frame is a candidate for dropping if no 8x8 blocks differ by more than a threshold of hi, and if no more than frac blocks (1 meaning the whole image) differ by more than a threshold of lo.

Default value for hi is 64*12, default value for lo is 64*5, and default value for frac is 0.33.

9.88 negate

Negate input video.

It accepts an integer in input; if non-zero it negates the alpha component (if available). The default value in input is 0.

9.89 nnedi

Deinterlace video using neural network edge directed interpolation.

This filter accepts the following options:

weights

Mandatory option, without binary file filter can not work. Currently file can be found here: https://github.com/dubhater/vapoursynth-nnedi3/blob/master/src/nnedi3_weights.bin

deint

Set which frames to deinterlace, by default it is all. Can be all or interlaced.

field

Set mode of operation.

Can be one of the following:

af

Use frame flags, both fields.

a

Use frame flags, single field.

t

Use top field only.

b

Use bottom field only.

tf

Use both fields, top first.

bf

Use both fields, bottom first.

planes

Set which planes to process, by default filter process all frames.

nsize

Set size of local neighborhood around each pixel, used by the predictor neural network.

Can be one of the following:

s8x6
s16x6
s32x6
s48x6
s8x4
s16x4
s32x4
nns

Set the number of neurons in predicctor neural network. Can be one of the following:

n16
n32
n64
n128
n256
qual

Controls the number of different neural network predictions that are blended together to compute the final output value. Can be fast, default or slow.

etype

Set which set of weights to use in the predictor. Can be one of the following:

a

weights trained to minimize absolute error

s

weights trained to minimize squared error

pscrn

Controls whether or not the prescreener neural network is used to decide which pixels should be processed by the predictor neural network and which can be handled by simple cubic interpolation. The prescreener is trained to know whether cubic interpolation will be sufficient for a pixel or whether it should be predicted by the predictor nn. The computational complexity of the prescreener nn is much less than that of the predictor nn. Since most pixels can be handled by cubic interpolation, using the prescreener generally results in much faster processing. The prescreener is pretty accurate, so the difference between using it and not using it is almost always unnoticeable.

Can be one of the following:

none
original
new

Default is new.

fapprox

Set various debugging flags.

9.90 noformat

Force libavfilter not to use any of the specified pixel formats for the input to the next filter.

It accepts the following parameters:

pix_fmts

A ’|’-separated list of pixel format names, such as apix_fmts=yuv420p|monow|rgb24".

9.90.1 Examples

  • Force libavfilter to use a format different from yuv420p for the input to the vflip filter:
    noformat=pix_fmts=yuv420p,vflip
    
  • Convert the input video to any of the formats not contained in the list:
    noformat=yuv420p|yuv444p|yuv410p
    

9.91 noise

Add noise on video input frame.

The filter accepts the following options:

all_seed
c0_seed
c1_seed
c2_seed
c3_seed

Set noise seed for specific pixel component or all pixel components in case of all_seed. Default value is 123457.

all_strength, alls
c0_strength, c0s
c1_strength, c1s
c2_strength, c2s
c3_strength, c3s

Set noise strength for specific pixel component or all pixel components in case all_strength. Default value is 0. Allowed range is [0, 100].

all_flags, allf
c0_flags, c0f
c1_flags, c1f
c2_flags, c2f
c3_flags, c3f

Set pixel component flags or set flags for all components if all_flags. Available values for component flags are:

a

averaged temporal noise (smoother)

p

mix random noise with a (semi)regular pattern

t

temporal noise (noise pattern changes between frames)

u

uniform noise (gaussian otherwise)

9.91.1 Examples

Add temporal and uniform noise to input video:

noise=alls=20:allf=t+u

9.92 null

Pass the video source unchanged to the output.

9.93 ocr

Optical Character Recognition

This filter uses Tesseract for optical character recognition.

It accepts the following options:

datapath

Set datapath to tesseract data. Default is to use whatever was set at installation.

language

Set language, default is "eng".

whitelist

Set character whitelist.

blacklist

Set character blacklist.

The filter exports recognized text as the frame metadata lavfi.ocr.text.

9.94 ocv

Apply a video transform using libopencv.

To enable this filter, install the libopencv library and headers and configure FFmpeg with --enable-libopencv.

It accepts the following parameters:

filter_name

The name of the libopencv filter to apply.

filter_params

The parameters to pass to the libopencv filter. If not specified, the default values are assumed.

Refer to the official libopencv documentation for more precise information: http://docs.opencv.org/master/modules/imgproc/doc/filtering.html

Several libopencv filters are supported; see the following subsections.

9.94.1 dilate

Dilate an image by using a specific structuring element. It corresponds to the libopencv function cvDilate.

It accepts the parameters: struct_el|nb_iterations.

struct_el represents a structuring element, and has the syntax: colsxrows+anchor_xxanchor_y/shape

cols and rows represent the number of columns and rows of the structuring element, anchor_x and anchor_y the anchor point, and shape the shape for the structuring element. shape must be "rect", "cross", "ellipse", or "custom".

If the value for shape is "custom", it must be followed by a string of the form "=filename". The file with name filename is assumed to represent a binary image, with each printable character corresponding to a bright pixel. When a custom shape is used, cols and rows are ignored, the number or columns and rows of the read file are assumed instead.

The default value for struct_el is "3x3+0x0/rect".

nb_iterations specifies the number of times the transform is applied to the image, and defaults to 1.

Some examples:

# Use the default values
ocv=dilate

# Dilate using a structuring element with a 5x5 cross, iterating two times
ocv=filter_name=dilate:filter_params=5x5+2x2/cross|2

# Read the shape from the file diamond.shape, iterating two times.
# The file diamond.shape may contain a pattern of characters like this
#   *
#  ***
# *****
#  ***
#   *
# The specified columns and rows are ignored
# but the anchor point coordinates are not
ocv=dilate:0x0+2x2/custom=diamond.shape|2

9.94.2 erode

Erode an image by using a specific structuring element. It corresponds to the libopencv function cvErode.

It accepts the parameters: struct_el:nb_iterations, with the same syntax and semantics as the dilate filter.

9.94.3 smooth

Smooth the input video.

The filter takes the following parameters: type|param1|param2|param3|param4.

type is the type of smooth filter to apply, and must be one of the following values: "blur", "blur_no_scale", "median", "gaussian", or "bilateral". The default value is "gaussian".

The meaning of param1, param2, param3, and param4 depend on the smooth type. param1 and param2 accept integer positive values or 0. param3 and param4 accept floating point values.

The default value for param1 is 3. The default value for the other parameters is 0.

These parameters correspond to the parameters assigned to the libopencv function cvSmooth.

9.95 overlay

Overlay one video on top of another.

It takes two inputs and has one output. The first input is the "main" video on which the second input is overlaid.

It accepts the following parameters:

A description of the accepted options follows.

x
y

Set the expression for the x and y coordinates of the overlaid video on the main video. Default value is "0" for both expressions. In case the expression is invalid, it is set to a huge value (meaning that the overlay will not be displayed within the output visible area).

eof_action

The action to take when EOF is encountered on the secondary input; it accepts one of the following values:

repeat

Repeat the last frame (the default).

endall

End both streams.

pass

Pass the main input through.

eval

Set when the expressions for x, and y are evaluated.

It accepts the following values:

init

only evaluate expressions once during the filter initialization or when a command is processed

frame

evaluate expressions for each incoming frame

Default value is ‘frame’.

shortest

If set to 1, force the output to terminate when the shortest input terminates. Default value is 0.

format

Set the format for the output video.

It accepts the following values:

yuv420

force YUV420 output

yuv422

force YUV422 output

yuv444

force YUV444 output

rgb

force RGB output

Default value is ‘yuv420’.

rgb (deprecated)

If set to 1, force the filter to accept inputs in the RGB color space. Default value is 0. This option is deprecated, use format instead.

repeatlast

If set to 1, force the filter to draw the last overlay frame over the main input until the end of the stream. A value of 0 disables this behavior. Default value is 1.

The x, and y expressions can contain the following parameters.

main_w, W
main_h, H

The main input width and height.

overlay_w, w
overlay_h, h

The overlay input width and height.

x
y

The computed values for x and y. They are evaluated for each new frame.

hsub
vsub

horizontal and vertical chroma subsample values of the output format. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

n

the number of input frame, starting from 0

pos

the position in the file of the input frame, NAN if unknown

t

The timestamp, expressed in seconds. It’s NAN if the input timestamp is unknown.

Note that the n, pos, t variables are available only when evaluation is done per frame, and will evaluate to NAN when eval is set to ‘init’.

Be aware that frames are taken from each input video in timestamp order, hence, if their initial timestamps differ, it is a good idea to pass the two inputs through a setpts=PTS-STARTPTS filter to have them begin in the same zero timestamp, as the example for the movie filter does.

You can chain together more overlays but you should test the efficiency of such approach.

9.95.1 Commands

This filter supports the following commands:

x
y

Modify the x and y of the overlay input. The command accepts the same syntax of the corresponding option.

If the specified expression is not valid, it is kept at its current value.

9.95.2 Examples

  • Draw the overlay at 10 pixels from the bottom right corner of the main video:
    overlay=main_w-overlay_w-10:main_h-overlay_h-10
    

    Using named options the example above becomes:

    overlay=x=main_w-overlay_w-10:y=main_h-overlay_h-10
    
  • Insert a transparent PNG logo in the bottom left corner of the input, using the ffmpeg tool with the -filter_complex option:
    ffmpeg -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output
    
  • Insert 2 different transparent PNG logos (second logo on bottom right corner) using the ffmpeg tool:
    ffmpeg -i input -i logo1 -i logo2 -filter_complex 'overlay=x=10:y=H-h-10,overlay=x=W-w-10:y=H-h-10' output
    
  • Add a transparent color layer on top of the main video; WxH must specify the size of the main input to the overlay filter:
    color=color=red@.3:size=WxH [over]; [in][over] overlay [out]
    
  • Play an original video and a filtered version (here with the deshake filter) side by side using the ffplay tool:
    ffplay input.avi -vf 'split[a][b]; [a]pad=iw*2:ih[src]; [b]deshake[filt]; [src][filt]overlay=w'
    

    The above command is the same as:

    ffplay input.avi -vf 'split[b], pad=iw*2[src], [b]deshake, [src]overlay=w'
    
  • Make a sliding overlay appearing from the left to the right top part of the screen starting since time 2:
    overlay=x='if(gte(t,2), -w+(t-2)*20, NAN)':y=0
    
  • Compose output by putting two input videos side to side:
    ffmpeg -i left.avi -i right.avi -filter_complex "
    nullsrc=size=200x100 [background];
    [0:v] setpts=PTS-STARTPTS, scale=100x100 [left];
    [1:v] setpts=PTS-STARTPTS, scale=100x100 [right];
    [background][left]       overlay=shortest=1       [background+left];
    [background+left][right] overlay=shortest=1:x=100 [left+right]
    "
    
  • Mask 10-20 seconds of a video by applying the delogo filter to a section
    ffmpeg -i test.avi -codec:v:0 wmv2 -ar 11025 -b:v 9000k
    -vf '[in]split[split_main][split_delogo];[split_delogo]trim=start=360:end=371,delogo=0:0:640:480[delogoed];[split_main][delogoed]overlay=eof_action=pass[out]'
    masked.avi
    
  • Chain several overlays in cascade:
    nullsrc=s=200x200 [bg];
    testsrc=s=100x100, split=4 [in0][in1][in2][in3];
    [in0] lutrgb=r=0, [bg]   overlay=0:0     [mid0];
    [in1] lutrgb=g=0, [mid0] overlay=100:0   [mid1];
    [in2] lutrgb=b=0, [mid1] overlay=0:100   [mid2];
    [in3] null,       [mid2] overlay=100:100 [out0]
    

9.96 owdenoise

Apply Overcomplete Wavelet denoiser.

The filter accepts the following options:

depth

Set depth.

Larger depth values will denoise lower frequency components more, but slow down filtering.

Must be an int in the range 8-16, default is 8.

luma_strength, ls

Set luma strength.

Must be a double value in the range 0-1000, default is 1.0.

chroma_strength, cs

Set chroma strength.

Must be a double value in the range 0-1000, default is 1.0.

9.97 pad

Add paddings to the input image, and place the original input at the provided x, y coordinates.

It accepts the following parameters:

width, w
height, h

Specify an expression for the size of the output image with the paddings added. If the value for width or height is 0, the corresponding input size is used for the output.

The width expression can reference the value set by the height expression, and vice versa.

The default value of width and height is 0.

x
y

Specify the offsets to place the input image at within the padded area, with respect to the top/left border of the output image.

The x expression can reference the value set by the y expression, and vice versa.

The default value of x and y is 0.

color

Specify the color of the padded area. For the syntax of this option, check the "Color" section in the ffmpeg-utils manual.

The default value of color is "black".

The value for the width, height, x, and y options are expressions containing the following constants:

in_w
in_h

The input video width and height.

iw
ih

These are the same as in_w and in_h.

out_w
out_h

The output width and height (the size of the padded area), as specified by the width and height expressions.

ow
oh

These are the same as out_w and out_h.

x
y

The x and y offsets as specified by the x and y expressions, or NAN if not yet specified.

a

same as iw / ih

sar

input sample aspect ratio

dar

input display aspect ratio, it is the same as (iw / ih) * sar

hsub
vsub

The horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

9.97.1 Examples

  • Add paddings with the color "violet" to the input video. The output video size is 640x480, and the top-left corner of the input video is placed at column 0, row 40
    pad=640:480:0:40:violet
    

    The example above is equivalent to the following command:

    pad=width=640:height=480:x=0:y=40:color=violet
    
  • Pad the input to get an output with dimensions increased by 3/2, and put the input video at the center of the padded area:
    pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
    
  • Pad the input to get a squared output with size equal to the maximum value between the input width and height, and put the input video at the center of the padded area:
    pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
    
  • Pad the input to get a final w/h ratio of 16:9:
    pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
    
  • In case of anamorphic video, in order to set the output display aspect correctly, it is necessary to use sar in the expression, according to the relation:
    (ih * X / ih) * sar = output_dar
    X = output_dar / sar
    

    Thus the previous example needs to be modified to:

    pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"
    
  • Double the output size and put the input video in the bottom-right corner of the output padded area:
    pad="2*iw:2*ih:ow-iw:oh-ih"
    

9.98 palettegen

Generate one palette for a whole video stream.

It accepts the following options:

max_colors

Set the maximum number of colors to quantize in the palette. Note: the palette will still contain 256 colors; the unused palette entries will be black.

reserve_transparent

Create a palette of 255 colors maximum and reserve the last one for transparency. Reserving the transparency color is useful for GIF optimization. If not set, the maximum of colors in the palette will be 256. You probably want to disable this option for a standalone image. Set by default.

stats_mode

Set statistics mode.

It accepts the following values:

full

Compute full frame histograms.

diff

Compute histograms only for the part that differs from previous frame. This might be relevant to give more importance to the moving part of your input if the background is static.

Default value is full.

The filter also exports the frame metadata lavfi.color_quant_ratio (nb_color_in / nb_color_out) which you can use to evaluate the degree of color quantization of the palette. This information is also visible at info logging level.

9.98.1 Examples

  • Generate a representative palette of a given video using ffmpeg:
    ffmpeg -i input.mkv -vf palettegen palette.png
    

9.99 paletteuse

Use a palette to downsample an input video stream.

The filter takes two inputs: one video stream and a palette. The palette must be a 256 pixels image.

It accepts the following options:

dither

Select dithering mode. Available algorithms are:

bayer

Ordered 8x8 bayer dithering (deterministic)

heckbert

Dithering as defined by Paul Heckbert in 1982 (simple error diffusion). Note: this dithering is sometimes considered "wrong" and is included as a reference.

floyd_steinberg

Floyd and Steingberg dithering (error diffusion)

sierra2

Frankie Sierra dithering v2 (error diffusion)

sierra2_4a

Frankie Sierra dithering v2 "Lite" (error diffusion)

Default is sierra2_4a.

bayer_scale

When bayer dithering is selected, this option defines the scale of the pattern (how much the crosshatch pattern is visible). A low value means more visible pattern for less banding, and higher value means less visible pattern at the cost of more banding.

The option must be an integer value in the range [0,5]. Default is 2.

diff_mode

If set, define the zone to process

rectangle

Only the changing rectangle will be reprocessed. This is similar to GIF cropping/offsetting compression mechanism. This option can be useful for speed if only a part of the image is changing, and has use cases such as limiting the scope of the error diffusal dither to the rectangle that bounds the moving scene (it leads to more deterministic output if the scene doesn’t change much, and as a result less moving noise and better GIF compression).

Default is none.

9.99.1 Examples

  • Use a palette (generated for example with palettegen) to encode a GIF using ffmpeg:
    ffmpeg -i input.mkv -i palette.png -lavfi paletteuse output.gif
    

9.100 perspective

Correct perspective of video not recorded perpendicular to the screen.

A description of the accepted parameters follows.

x0
y0
x1
y1
x2
y2
x3
y3

Set coordinates expression for top left, top right, bottom left and bottom right corners. Default values are 0:0:W:0:0:H:W:H with which perspective will remain unchanged. If the sense option is set to source, then the specified points will be sent to the corners of the destination. If the sense option is set to destination, then the corners of the source will be sent to the specified coordinates.

The expressions can use the following variables:

W
H

the width and height of video frame.

in

Input frame count.

on

Output frame count.

interpolation

Set interpolation for perspective correction.

It accepts the following values:

linear
cubic

Default value is ‘linear’.

sense

Set interpretation of coordinate options.

It accepts the following values:

0, source

Send point in the source specified by the given coordinates to the corners of the destination.

1, destination

Send the corners of the source to the point in the destination specified by the given coordinates.

Default value is ‘source’.

eval

Set when the expressions for coordinates x0,y0,...x3,y3 are evaluated.

It accepts the following values:

init

only evaluate expressions once during the filter initialization or when a command is processed

frame

evaluate expressions for each incoming frame

Default value is ‘init’.

9.101 phase

Delay interlaced video by one field time so that the field order changes.

The intended use is to fix PAL movies that have been captured with the opposite field order to the film-to-video transfer.

A description of the accepted parameters follows.

mode

Set phase mode.

It accepts the following values:

t

Capture field order top-first, transfer bottom-first. Filter will delay the bottom field.

b

Capture field order bottom-first, transfer top-first. Filter will delay the top field.

p

Capture and transfer with the same field order. This mode only exists for the documentation of the other options to refer to, but if you actually select it, the filter will faithfully do nothing.

a

Capture field order determined automatically by field flags, transfer opposite. Filter selects among ‘t’ and ‘b’ modes on a frame by frame basis using field flags. If no field information is available, then this works just like ‘u’.

u

Capture unknown or varying, transfer opposite. Filter selects among ‘t’ and ‘b’ on a frame by frame basis by analyzing the images and selecting the alternative that produces best match between the fields.

T

Capture top-first, transfer unknown or varying. Filter selects among ‘t’ and ‘p’ using image analysis.

B

Capture bottom-first, transfer unknown or varying. Filter selects among ‘b’ and ‘p’ using image analysis.

A

Capture determined by field flags, transfer unknown or varying. Filter selects among ‘t’, ‘b’ and ‘p’ using field flags and image analysis. If no field information is available, then this works just like ‘U’. This is the default mode.

U

Both capture and transfer unknown or varying. Filter selects among ‘t’, ‘b’ and ‘p’ using image analysis only.

9.102 pixdesctest

Pixel format descriptor test filter, mainly useful for internal testing. The output video should be equal to the input video.

For example:

format=monow, pixdesctest

can be used to test the monowhite pixel format descriptor definition.

9.103 pp

Enable the specified chain of postprocessing subfilters using libpostproc. This library should be automatically selected with a GPL build (--enable-gpl). Subfilters must be separated by ’/’ and can be disabled by prepending a ’-’. Each subfilter and some options have a short and a long name that can be used interchangeably, i.e. dr/dering are the same.

The filters accept the following options:

subfilters

Set postprocessing subfilters string.

All subfilters share common options to determine their scope:

a/autoq

Honor the quality commands for this subfilter.

c/chrom

Do chrominance filtering, too (default).

y/nochrom

Do luminance filtering only (no chrominance).

n/noluma

Do chrominance filtering only (no luminance).

These options can be appended after the subfilter name, separated by a ’|’.

Available subfilters are:

hb/hdeblock[|difference[|flatness]]

Horizontal deblocking filter

difference

Difference factor where higher values mean more deblocking (default: 32).

flatness

Flatness threshold where lower values mean more deblocking (default: 39).

vb/vdeblock[|difference[|flatness]]

Vertical deblocking filter

difference

Difference factor where higher values mean more deblocking (default: 32).

flatness

Flatness threshold where lower values mean more deblocking (default: 39).

ha/hadeblock[|difference[|flatness]]

Accurate horizontal deblocking filter

difference

Difference factor where higher values mean more deblocking (default: 32).

flatness

Flatness threshold where lower values mean more deblocking (default: 39).

va/vadeblock[|difference[|flatness]]

Accurate vertical deblocking filter

difference

Difference factor where higher values mean more deblocking (default: 32).

flatness

Flatness threshold where lower values mean more deblocking (default: 39).

The horizontal and vertical deblocking filters share the difference and flatness values so you cannot set different horizontal and vertical thresholds.

h1/x1hdeblock

Experimental horizontal deblocking filter

v1/x1vdeblock

Experimental vertical deblocking filter

dr/dering

Deringing filter

tn/tmpnoise[|threshold1[|threshold2[|threshold3]]], temporal noise reducer
threshold1

larger -> stronger filtering

threshold2

larger -> stronger filtering

threshold3

larger -> stronger filtering

al/autolevels[:f/fullyrange], automatic brightness / contrast correction
f/fullyrange

Stretch luminance to 0-255.

lb/linblenddeint

Linear blend deinterlacing filter that deinterlaces the given block by filtering all lines with a (1 2 1) filter.

li/linipoldeint

Linear interpolating deinterlacing filter that deinterlaces the given block by linearly interpolating every second line.

ci/cubicipoldeint

Cubic interpolating deinterlacing filter deinterlaces the given block by cubically interpolating every second line.

md/mediandeint

Median deinterlacing filter that deinterlaces the given block by applying a median filter to every second line.

fd/ffmpegdeint

FFmpeg deinterlacing filter that deinterlaces the given block by filtering every second line with a (-1 4 2 4 -1) filter.

l5/lowpass5

Vertically applied FIR lowpass deinterlacing filter that deinterlaces the given block by filtering all lines with a (-1 2 6 2 -1) filter.

fq/forceQuant[|quantizer]

Overrides the quantizer table from the input with the constant quantizer you specify.

quantizer

Quantizer to use

de/default

Default pp filter combination (hb|a,vb|a,dr|a)

fa/fast

Fast pp filter combination (h1|a,v1|a,dr|a)

ac

High quality pp filter combination (ha|a|128|7,va|a,dr|a)

9.103.1 Examples

  • Apply horizontal and vertical deblocking, deringing and automatic brightness/contrast:
    pp=hb/vb/dr/al
    
  • Apply default filters without brightness/contrast correction:
    pp=de/-al
    
  • Apply default filters and temporal denoiser:
    pp=default/tmpnoise|1|2|3
    
  • Apply deblocking on luminance only, and switch vertical deblocking on or off automatically depending on available CPU time:
    pp=hb|y/vb|a
    

9.104 pp7

Apply Postprocessing filter 7. It is variant of the spp filter, similar to spp = 6 with 7 point DCT, where only the center sample is used after IDCT.

The filter accepts the following options:

qp

Force a constant quantization parameter. It accepts an integer in range 0 to 63. If not set, the filter will use the QP from the video stream (if available).

mode

Set thresholding mode. Available modes are:

hard

Set hard thresholding.

soft

Set soft thresholding (better de-ringing effect, but likely blurrier).

medium

Set medium thresholding (good results, default).

9.105 psnr

Obtain the average, maximum and minimum PSNR (Peak Signal to Noise Ratio) between two input videos.

This filter takes in input two input videos, the first input is considered the "main" source and is passed unchanged to the output. The second input is used as a "reference" video for computing the PSNR.

Both video inputs must have the same resolution and pixel format for this filter to work correctly. Also it assumes that both inputs have the same number of frames, which are compared one by one.

The obtained average PSNR is printed through the logging system.

The filter stores the accumulated MSE (mean squared error) of each frame, and at the end of the processing it is averaged across all frames equally, and the following formula is applied to obtain the PSNR:

PSNR = 10*log10(MAX^2/MSE)

Where MAX is the average of the maximum values of each component of the image.

The description of the accepted parameters follows.

stats_file, f

If specified the filter will use the named file to save the PSNR of each individual frame. When filename equals "-" the data is sent to standard output.

The file printed if stats_file is selected, contains a sequence of key/value pairs of the form key:value for each compared couple of frames.

A description of each shown parameter follows:

n

sequential number of the input frame, starting from 1

mse_avg

Mean Square Error pixel-by-pixel average difference of the compared frames, averaged over all the image components.

mse_y, mse_u, mse_v, mse_r, mse_g, mse_g, mse_a

Mean Square Error pixel-by-pixel average difference of the compared frames for the component specified by the suffix.

psnr_y, psnr_u, psnr_v, psnr_r, psnr_g, psnr_b, psnr_a

Peak Signal to Noise ratio of the compared frames for the component specified by the suffix.

For example:

movie=ref_movie.mpg, setpts=PTS-STARTPTS [main];
[main][ref] psnr="stats_file=stats.log" [out]

On this example the input file being processed is compared with the reference file ref_movie.mpg. The PSNR of each individual frame is stored in stats.log.

9.106 pullup

Pulldown reversal (inverse telecine) filter, capable of handling mixed hard-telecine, 24000/1001 fps progressive, and 30000/1001 fps progressive content.

The pullup filter is designed to take advantage of future context in making its decisions. This filter is stateless in the sense that it does not lock onto a pattern to follow, but it instead looks forward to the following fields in order to identify matches and rebuild progressive frames.

To produce content with an even framerate, insert the fps filter after pullup, use fps=24000/1001 if the input frame rate is 29.97fps, fps=24 for 30fps and the (rare) telecined 25fps input.

The filter accepts the following options:

jl
jr
jt
jb

These options set the amount of "junk" to ignore at the left, right, top, and bottom of the image, respectively. Left and right are in units of 8 pixels, while top and bottom are in units of 2 lines. The default is 8 pixels on each side.

sb

Set the strict breaks. Setting this option to 1 will reduce the chances of filter generating an occasional mismatched frame, but it may also cause an excessive number of frames to be dropped during high motion sequences. Conversely, setting it to -1 will make filter match fields more easily. This may help processing of video where there is slight blurring between the fields, but may also cause there to be interlaced frames in the output. Default value is 0.

mp

Set the metric plane to use. It accepts the following values:

l

Use luma plane.

u

Use chroma blue plane.

v

Use chroma red plane.

This option may be set to use chroma plane instead of the default luma plane for doing filter’s computations. This may improve accuracy on very clean source material, but more likely will decrease accuracy, especially if there is chroma noise (rainbow effect) or any grayscale video. The main purpose of setting mp to a chroma plane is to reduce CPU load and make pullup usable in realtime on slow machines.

For best results (without duplicated frames in the output file) it is necessary to change the output frame rate. For example, to inverse telecine NTSC input:

ffmpeg -i input -vf pullup -r 24000/1001 ...

9.107 qp

Change video quantization parameters (QP).

The filter accepts the following option:

qp

Set expression for quantization parameter.

The expression is evaluated through the eval API and can contain, among others, the following constants:

known

1 if index is not 129, 0 otherwise.

qp

Sequentional index starting from -129 to 128.

9.107.1 Examples

  • Some equation like:
    qp=2+2*sin(PI*qp)
    

9.108 random

Flush video frames from internal cache of frames into a random order. No frame is discarded. Inspired by frei0r nervous filter.

frames

Set size in number of frames of internal cache, in range from 2 to 512. Default is 30.

seed

Set seed for random number generator, must be an integer included between 0 and UINT32_MAX. If not specified, or if explicitly set to less than 0, the filter will try to use a good random seed on a best effort basis.

9.109 readvitc

Read vertical interval timecode (VITC) information from the top lines of a video frame.

The filter adds frame metadata key lavfi.readvitc.tc_str with the timecode value, if a valid timecode has been detected. Further metadata key lavfi.readvitc.found is set to 0/1 depending on whether timecode data has been found or not.

This filter accepts the following options:

scan_max

Set the maximum number of lines to scan for VITC data. If the value is set to -1 the full video frame is scanned. Default is 45.

thr_b

Set the luma threshold for black. Accepts float numbers in the range [0.0,1.0], default value is 0.2. The value must be equal or less than thr_w.

thr_w

Set the luma threshold for white. Accepts float numbers in the range [0.0,1.0], default value is 0.6. The value must be equal or greater than thr_b.

9.109.1 Examples

  • Detect and draw VITC data onto the video frame; if no valid VITC is detected, draw --:--:--:-- as a placeholder:
    ffmpeg -i input.avi -filter:v 'readvitc,drawtext=fontfile=FreeMono.ttf:text=%{metadata\\:lavfi.readvitc.tc_str\\:--\\\\\\:--\\\\\\:--\\\\\\:--}:x=(w-tw)/2:y=400-ascent'
    

9.110 remap

Remap pixels using 2nd: Xmap and 3rd: Ymap input video stream.

Destination pixel at position (X, Y) will be picked from source (x, y) position where x = Xmap(X, Y) and y = Ymap(X, Y). If mapping values are out of range, zero value for pixel will be used for destination pixel.

Xmap and Ymap input video streams must be of same dimensions. Output video stream will have Xmap/Ymap video stream dimensions. Xmap and Ymap input video streams are 16bit depth, single channel.

9.111 removegrain

The removegrain filter is a spatial denoiser for progressive video.

m0

Set mode for the first plane.

m1

Set mode for the second plane.

m2

Set mode for the third plane.

m3

Set mode for the fourth plane.

Range of mode is from 0 to 24. Description of each mode follows:

0

Leave input plane unchanged. Default.

1

Clips the pixel with the minimum and maximum of the 8 neighbour pixels.

2

Clips the pixel with the second minimum and maximum of the 8 neighbour pixels.

3

Clips the pixel with the third minimum and maximum of the 8 neighbour pixels.

4

Clips the pixel with the fourth minimum and maximum of the 8 neighbour pixels. This is equivalent to a median filter.

5

Line-sensitive clipping giving the minimal change.

6

Line-sensitive clipping, intermediate.

7

Line-sensitive clipping, intermediate.

8

Line-sensitive clipping, intermediate.

9

Line-sensitive clipping on a line where the neighbours pixels are the closest.

10

Replaces the target pixel with the closest neighbour.

11

[1 2 1] horizontal and vertical kernel blur.

12

Same as mode 11.

13

Bob mode, interpolates top field from the line where the neighbours pixels are the closest.

14

Bob mode, interpolates bottom field from the line where the neighbours pixels are the closest.

15

Bob mode, interpolates top field. Same as 13 but with a more complicated interpolation formula.

16

Bob mode, interpolates bottom field. Same as 14 but with a more complicated interpolation formula.

17

Clips the pixel with the minimum and maximum of respectively the maximum and minimum of each pair of opposite neighbour pixels.

18

Line-sensitive clipping using opposite neighbours whose greatest distance from the current pixel is minimal.

19

Replaces the pixel with the average of its 8 neighbours.

20

Averages the 9 pixels ([1 1 1] horizontal and vertical blur).

21

Clips pixels using the averages of opposite neighbour.

22

Same as mode 21 but simpler and faster.

23

Small edge and halo removal, but reputed useless.

24

Similar as 23.

9.112 removelogo

Suppress a TV station logo, using an image file to determine which pixels comprise the logo. It works by filling in the pixels that comprise the logo with neighboring pixels.

The filter accepts the following options:

filename, f

Set the filter bitmap file, which can be any image format supported by libavformat. The width and height of the image file must match those of the video stream being processed.

Pixels in the provided bitmap image with a value of zero are not considered part of the logo, non-zero pixels are considered part of the logo. If you use white (255) for the logo and black (0) for the rest, you will be safe. For making the filter bitmap, it is recommended to take a screen capture of a black frame with the logo visible, and then using a threshold filter followed by the erode filter once or twice.

If needed, little splotches can be fixed manually. Remember that if logo pixels are not covered, the filter quality will be much reduced. Marking too many pixels as part of the logo does not hurt as much, but it will increase the amount of blurring needed to cover over the image and will destroy more information than necessary, and extra pixels will slow things down on a large logo.

9.113 repeatfields

This filter uses the repeat_field flag from the Video ES headers and hard repeats fields based on its value.

9.114 reverse, areverse

Reverse a clip.

Warning: This filter requires memory to buffer the entire clip, so trimming is suggested.

9.114.1 Examples

  • Take the first 5 seconds of a clip, and reverse it.
    trim=end=5,reverse
    

9.115 rotate

Rotate video by an arbitrary angle expressed in radians.

The filter accepts the following options:

A description of the optional parameters follows.

angle, a

Set an expression for the angle by which to rotate the input video clockwise, expressed as a number of radians. A negative value will result in a counter-clockwise rotation. By default it is set to "0".

This expression is evaluated for each frame.

out_w, ow

Set the output width expression, default value is "iw". This expression is evaluated just once during configuration.

out_h, oh

Set the output height expression, default value is "ih". This expression is evaluated just once during configuration.

bilinear

Enable bilinear interpolation if set to 1, a value of 0 disables it. Default value is 1.

fillcolor, c

Set the color used to fill the output area not covered by the rotated image. For the general syntax of this option, check the "Color" section in the ffmpeg-utils manual. If the special value "none" is selected then no background is printed (useful for example if the background is never shown).

Default value is "black".

The expressions for the angle and the output size can contain the following constants and functions:

n

sequential number of the input frame, starting from 0. It is always NAN before the first frame is filtered.

t

time in seconds of the input frame, it is set to 0 when the filter is configured. It is always NAN before the first frame is filtered.

hsub
vsub

horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

in_w, iw
in_h, ih

the input video width and height

out_w, ow
out_h, oh

the output width and height, that is the size of the padded area as specified by the width and height expressions

rotw(a)
roth(a)

the minimal width/height required for completely containing the input video rotated by a radians.

These are only available when computing the out_w and out_h expressions.

9.115.1 Examples

  • Rotate the input by PI/6 radians clockwise:
    rotate=PI/6
    
  • Rotate the input by PI/6 radians counter-clockwise:
    rotate=-PI/6
    
  • Rotate the input by 45 degrees clockwise:
    rotate=45*PI/180
    
  • Apply a constant rotation with period T, starting from an angle of PI/3:
    rotate=PI/3+2*PI*t/T
    
  • Make the input video rotation oscillating with a period of T seconds and an amplitude of A radians:
    rotate=A*sin(2*PI/T*t)
    
  • Rotate the video, output size is chosen so that the whole rotating input video is always completely contained in the output:
    rotate='2*PI*t:ow=hypot(iw,ih):oh=ow'
    
  • Rotate the video, reduce the output size so that no background is ever shown:
    rotate=2*PI*t:ow='min(iw,ih)/sqrt(2)':oh=ow:c=none
    

9.115.2 Commands

The filter supports the following commands:

a, angle

Set the angle expression. The command accepts the same syntax of the corresponding option.

If the specified expression is not valid, it is kept at its current value.

9.116 sab

Apply Shape Adaptive Blur.

The filter accepts the following options:

luma_radius, lr

Set luma blur filter strength, must be a value in range 0.1-4.0, default value is 1.0. A greater value will result in a more blurred image, and in slower processing.

luma_pre_filter_radius, lpfr

Set luma pre-filter radius, must be a value in the 0.1-2.0 range, default value is 1.0.

luma_strength, ls

Set luma maximum difference between pixels to still be considered, must be a value in the 0.1-100.0 range, default value is 1.0.

chroma_radius, cr

Set chroma blur filter strength, must be a value in range 0.1-4.0. A greater value will result in a more blurred image, and in slower processing.

chroma_pre_filter_radius, cpfr

Set chroma pre-filter radius, must be a value in the 0.1-2.0 range.

chroma_strength, cs

Set chroma maximum difference between pixels to still be considered, must be a value in the 0.1-100.0 range.

Each chroma option value, if not explicitly specified, is set to the corresponding luma option value.

9.117 scale

Scale (resize) the input video, using the libswscale library.

The scale filter forces the output display aspect ratio to be the same of the input, by changing the output sample aspect ratio.

If the input image format is different from the format requested by the next filter, the scale filter will convert the input to the requested format.

9.117.1 Options

The filter accepts the following options, or any of the options supported by the libswscale scaler.

See (ffmpeg-scaler)the ffmpeg-scaler manual for the complete list of scaler options.

width, w
height, h

Set the output video dimension expression. Default value is the input dimension.

If the value is 0, the input width is used for the output.

If one of the values is -1, the scale filter will use a value that maintains the aspect ratio of the input image, calculated from the other specified dimension. If both of them are -1, the input size is used

If one of the values is -n with n > 1, the scale filter will also use a value that maintains the aspect ratio of the input image, calculated from the other specified dimension. After that it will, however, make sure that the calculated dimension is divisible by n and adjust the value if necessary.

See below for the list of accepted constants for use in the dimension expression.

eval

Specify when to evaluate width and height expression. It accepts the following values:

init

Only evaluate expressions once during the filter initialization or when a command is processed.

frame

Evaluate expressions for each incoming frame.

Default value is ‘init’.

interl

Set the interlacing mode. It accepts the following values:

1

Force interlaced aware scaling.

0

Do not apply interlaced scaling.

-1

Select interlaced aware scaling depending on whether the source frames are flagged as interlaced or not.

Default value is ‘0’.

flags

Set libswscale scaling flags. See (ffmpeg-scaler)the ffmpeg-scaler manual for the complete list of values. If not explicitly specified the filter applies the default flags.

param0, param1

Set libswscale input parameters for scaling algorithms that need them. See (ffmpeg-scaler)the ffmpeg-scaler manual for the complete documentation. If not explicitly specified the filter applies empty parameters.

size, s

Set the video size. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual.

in_color_matrix
out_color_matrix

Set in/output YCbCr color space type.

This allows the autodetected value to be overridden as well as allows forcing a specific value used for the output and encoder.

If not specified, the color space type depends on the pixel format.

Possible values:

auto

Choose automatically.

bt709

Format conforming to International Telecommunication Union (ITU) Recommendation BT.709.

fcc

Set color space conforming to the United States Federal Communications Commission (FCC) Code of Federal Regulations (CFR) Title 47 (2003) 73.682 (a).

bt601

Set color space conforming to:

  • ITU Radiocommunication Sector (ITU-R) Recommendation BT.601
  • ITU-R Rec. BT.470-6 (1998) Systems B, B1, and G
  • Society of Motion Picture and Television Engineers (SMPTE) ST 170:2004
smpte240m

Set color space conforming to SMPTE ST 240:1999.

in_range
out_range

Set in/output YCbCr sample range.

This allows the autodetected value to be overridden as well as allows forcing a specific value used for the output and encoder. If not specified, the range depends on the pixel format. Possible values:

auto

Choose automatically.

jpeg/full/pc

Set full range (0-255 in case of 8-bit luma).

mpeg/tv

Set "MPEG" range (16-235 in case of 8-bit luma).

force_original_aspect_ratio

Enable decreasing or increasing output video width or height if necessary to keep the original aspect ratio. Possible values:

disable

Scale the video as specified and disable this feature.

decrease

The output video dimensions will automatically be decreased if needed.

increase

The output video dimensions will automatically be increased if needed.

One useful instance of this option is that when you know a specific device’s maximum allowed resolution, you can use this to limit the output video to that, while retaining the aspect ratio. For example, device A allows 1280x720 playback, and your video is 1920x800. Using this option (set it to decrease) and specifying 1280x720 to the command line makes the output 1280x533.

Please note that this is a different thing than specifying -1 for w or h, you still need to specify the output resolution for this option to work.

The values of the w and h options are expressions containing the following constants:

in_w
in_h

The input width and height

iw
ih

These are the same as in_w and in_h.

out_w
out_h

The output (scaled) width and height

ow
oh

These are the same as out_w and out_h

a

The same as iw / ih

sar

input sample aspect ratio

dar

The input display aspect ratio. Calculated from (iw / ih) * sar.

hsub
vsub

horizontal and vertical input chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

ohsub
ovsub

horizontal and vertical output chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

9.117.2 Examples

  • Scale the input video to a size of 200x100
    scale=w=200:h=100
    

    This is equivalent to:

    scale=200:100
    

    or:

    scale=200x100
    
  • Specify a size abbreviation for the output size:
    scale=qcif
    

    which can also be written as:

    scale=size=qcif
    
  • Scale the input to 2x:
    scale=w=2*iw:h=2*ih
    
  • The above is the same as:
    scale=2*in_w:2*in_h
    
  • Scale the input to 2x with forced interlaced scaling:
    scale=2*iw:2*ih:interl=1
    
  • Scale the input to half size:
    scale=w=iw/2:h=ih/2
    
  • Increase the width, and set the height to the same size:
    scale=3/2*iw:ow
    
  • Seek Greek harmony:
    scale=iw:1/PHI*iw
    scale=ih*PHI:ih
    
  • Increase the height, and set the width to 3/2 of the height:
    scale=w=3/2*oh:h=3/5*ih
    
  • Increase the size, making the size a multiple of the chroma subsample values:
    scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
    
  • Increase the width to a maximum of 500 pixels, keeping the same aspect ratio as the input:
    scale=w='min(500\, iw*3/2):h=-1'
    

9.117.3 Commands

This filter supports the following commands:

width, w
height, h

Set the output video dimension expression. The command accepts the same syntax of the corresponding option.

If the specified expression is not valid, it is kept at its current value.

9.118 scale2ref

Scale (resize) the input video, based on a reference video.

See the scale filter for available options, scale2ref supports the same but uses the reference video instead of the main input as basis.

9.118.1 Examples

  • Scale a subtitle stream to match the main video in size before overlaying
    'scale2ref[b][a];[a][b]overlay'
    

9.119 selectivecolor

Adjust cyan, magenta, yellow and black (CMYK) to certain ranges of colors (such as "reds", "yellows", "greens", "cyans", ...). The adjustment range is defined by the "purity" of the color (that is, how saturated it already is).

This filter is similar to the Adobe Photoshop Selective Color tool.

The filter accepts the following options:

correction_method

Select color correction method.

Available values are:

absolute

Specified adjustments are applied "as-is" (added/subtracted to original pixel component value).

relative

Specified adjustments are relative to the original component value.

Default is absolute.

reds

Adjustments for red pixels (pixels where the red component is the maximum)

yellows

Adjustments for yellow pixels (pixels where the blue component is the minimum)

greens

Adjustments for green pixels (pixels where the green component is the maximum)

cyans

Adjustments for cyan pixels (pixels where the red component is the minimum)

blues

Adjustments for blue pixels (pixels where the blue component is the maximum)

magentas

Adjustments for magenta pixels (pixels where the green component is the minimum)

whites

Adjustments for white pixels (pixels where all components are greater than 128)

neutrals

Adjustments for all pixels except pure black and pure white

blacks

Adjustments for black pixels (pixels where all components are lesser than 128)

psfile

Specify a Photoshop selective color file (.asv) to import the settings from.

All the adjustment settings (reds, yellows, ...) accept up to 4 space separated floating point adjustment values in the [-1,1] range, respectively to adjust the amount of cyan, magenta, yellow and black for the pixels of its range.

9.119.1 Examples

  • Increase cyan by 50% and reduce yellow by 33% in every green areas, and increase magenta by 27% in blue areas:
    selectivecolor=greens=.5 0 -.33 0:blues=0 .27
    
  • Use a Photoshop selective color preset:
    selectivecolor=psfile=MySelectiveColorPresets/Misty.asv
    

9.120 separatefields

The separatefields takes a frame-based video input and splits each frame into its components fields, producing a new half height clip with twice the frame rate and twice the frame count.

This filter use field-dominance information in frame to decide which of each pair of fields to place first in the output. If it gets it wrong use setfield filter before separatefields filter.

9.121 setdar, setsar

The setdar filter sets the Display Aspect Ratio for the filter output video.

This is done by changing the specified Sample (aka Pixel) Aspect Ratio, according to the following equation:

DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR

Keep in mind that the setdar filter does not modify the pixel dimensions of the video frame. Also, the display aspect ratio set by this filter may be changed by later filters in the filterchain, e.g. in case of scaling or if another "setdar" or a "setsar" filter is applied.

The setsar filter sets the Sample (aka Pixel) Aspect Ratio for the filter output video.

Note that as a consequence of the application of this filter, the output display aspect ratio will change according to the equation above.

Keep in mind that the sample aspect ratio set by the setsar filter may be changed by later filters in the filterchain, e.g. if another "setsar" or a "setdar" filter is applied.

It accepts the following parameters:

r, ratio, dar (setdar only), sar (setsar only)

Set the aspect ratio used by the filter.

The parameter can be a floating point number string, an expression, or a string of the form num:den, where num and den are the numerator and denominator of the aspect ratio. If the parameter is not specified, it is assumed the value "0". In case the form "num:den" is used, the : character should be escaped.

max

Set the maximum integer value to use for expressing numerator and denominator when reducing the expressed aspect ratio to a rational. Default value is 100.

The parameter sar is an expression containing the following constants:

E, PI, PHI

These are approximated values for the mathematical constants e (Euler’s number), pi (Greek pi), and phi (the golden ratio).

w, h

The input width and height.

a

These are the same as w / h.

sar

The input sample aspect ratio.

dar

The input display aspect ratio. It is the same as (w / h) * sar.

hsub, vsub

Horizontal and vertical chroma subsample values. For example, for the pixel format "yuv422p" hsub is 2 and vsub is 1.

9.121.1 Examples

  • To change the display aspect ratio to 16:9, specify one of the following:
    setdar=dar=1.77777
    setdar=dar=16/9
    
  • To change the sample aspect ratio to 10:11, specify:
    setsar=sar=10/11
    
  • To set a display aspect ratio of 16:9, and specify a maximum integer value of 1000 in the aspect ratio reduction, use the command:
    setdar=ratio=16/9:max=1000
    

9.122 setfield

Force field for the output video frame.

The setfield filter marks the interlace type field for the output frames. It does not change the input frame, but only sets the corresponding property, which affects how the frame is treated by following filters (e.g. fieldorder or yadif).

The filter accepts the following options:

mode

Available values are:

auto

Keep the same field property.

bff

Mark the frame as bottom-field-first.

tff

Mark the frame as top-field-first.

prog

Mark the frame as progressive.

9.123 showinfo

Show a line containing various information for each input video frame. The input video is not modified.

The shown line contains a sequence of key/value pairs of the form key:value.

The following values are shown in the output:

n

The (sequential) number of the input frame, starting from 0.

pts

The Presentation TimeStamp of the input frame, expressed as a number of time base units. The time base unit depends on the filter input pad.

pts_time

The Presentation TimeStamp of the input frame, expressed as a number of seconds.

pos

The position of the frame in the input stream, or -1 if this information is unavailable and/or meaningless (for example in case of synthetic video).

fmt

The pixel format name.

sar

The sample aspect ratio of the input frame, expressed in the form num/den.

s

The size of the input frame. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual.

i

The type of interlaced mode ("P" for "progressive", "T" for top field first, "B" for bottom field first).

iskey

This is 1 if the frame is a key frame, 0 otherwise.

type

The picture type of the input frame ("I" for an I-frame, "P" for a P-frame, "B" for a B-frame, or "?" for an unknown type). Also refer to the documentation of the AVPictureType enum and of the av_get_picture_type_char function defined in libavutil/avutil.h.

checksum

The Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame.

plane_checksum

The Adler-32 checksum (printed in hexadecimal) of each plane of the input frame, expressed in the form "[c0 c1 c2 c3]".

9.124 showpalette

Displays the 256 colors palette of each frame. This filter is only relevant for pal8 pixel format frames.

It accepts the following option:

s

Set the size of the box used to represent one palette color entry. Default is 30 (for a 30x30 pixel box).

9.125 shuffleframes

Reorder and/or duplicate video frames.

It accepts the following parameters:

mapping

Set the destination indexes of input frames. This is space or ’|’ separated list of indexes that maps input frames to output frames. Number of indexes also sets maximal value that each index may have.

The first frame has the index 0. The default is to keep the input unchanged.

Swap second and third frame of every three frames of the input:

ffmpeg -i INPUT -vf "shuffleframes=0 2 1" OUTPUT

9.126 shuffleplanes

Reorder and/or duplicate video planes.

It accepts the following parameters:

map0

The index of the input plane to be used as the first output plane.

map1

The index of the input plane to be used as the second output plane.

map2

The index of the input plane to be used as the third output plane.

map3

The index of the input plane to be used as the fourth output plane.

The first plane has the index 0. The default is to keep the input unchanged.

Swap the second and third planes of the input:

ffmpeg -i INPUT -vf shuffleplanes=0:2:1:3 OUTPUT

9.127 signalstats

Evaluate various visual metrics that assist in determining issues associated with the digitization of analog video media.

By default the filter will log these metadata values:

YMIN

Display the minimal Y value contained within the input frame. Expressed in range of [0-255].

YLOW

Display the Y value at the 10% percentile within the input frame. Expressed in range of [0-255].

YAVG

Display the average Y value within the input frame. Expressed in range of [0-255].

YHIGH

Display the Y value at the 90% percentile within the input frame. Expressed in range of [0-255].

YMAX

Display the maximum Y value contained within the input frame. Expressed in range of [0-255].

UMIN

Display the minimal U value contained within the input frame. Expressed in range of [0-255].

ULOW

Display the U value at the 10% percentile within the input frame. Expressed in range of [0-255].

UAVG

Display the average U value within the input frame. Expressed in range of [0-255].

UHIGH

Display the U value at the 90% percentile within the input frame. Expressed in range of [0-255].

UMAX

Display the maximum U value contained within the input frame. Expressed in range of [0-255].

VMIN

Display the minimal V value contained within the input frame. Expressed in range of [0-255].

VLOW

Display the V value at the 10% percentile within the input frame. Expressed in range of [0-255].

VAVG

Display the average V value within the input frame. Expressed in range of [0-255].

VHIGH

Display the V value at the 90% percentile within the input frame. Expressed in range of [0-255].

VMAX

Display the maximum V value contained within the input frame. Expressed in range of [0-255].

SATMIN

Display the minimal saturation value contained within the input frame. Expressed in range of [0-~181.02].

SATLOW

Display the saturation value at the 10% percentile within the input frame. Expressed in range of [0-~181.02].

SATAVG

Display the average saturation value within the input frame. Expressed in range of [0-~181.02].

SATHIGH

Display the saturation value at the 90% percentile within the input frame. Expressed in range of [0-~181.02].

SATMAX

Display the maximum saturation value contained within the input frame. Expressed in range of [0-~181.02].

HUEMED

Display the median value for hue within the input frame. Expressed in range of [0-360].

HUEAVG

Display the average value for hue within the input frame. Expressed in range of [0-360].

YDIF

Display the average of sample value difference between all values of the Y plane in the current frame and corresponding values of the previous input frame. Expressed in range of [0-255].

UDIF

Display the average of sample value difference between all values of the U plane in the current frame and corresponding values of the previous input frame. Expressed in range of [0-255].

VDIF

Display the average of sample value difference between all values of the V plane in the current frame and corresponding values of the previous input frame. Expressed in range of [0-255].

The filter accepts the following options:

stat
out

stat specify an additional form of image analysis. out output video with the specified type of pixel highlighted.

Both options accept the following values:

tout

Identify temporal outliers pixels. A temporal outlier is a pixel unlike the neighboring pixels of the same field. Examples of temporal outliers include the results of video dropouts, head clogs, or tape tracking issues.

vrep

Identify vertical line repetition. Vertical line repetition includes similar rows of pixels within a frame. In born-digital video vertical line repetition is common, but this pattern is uncommon in video digitized from an analog source. When it occurs in video that results from the digitization of an analog source it can indicate concealment from a dropout compensator.

brng

Identify pixels that fall outside of legal broadcast range.

color, c

Set the highlight color for the out option. The default color is yellow.

9.127.1 Examples

  • Output data of various video metrics:
    ffprobe -f lavfi movie=example.mov,signalstats="stat=tout+vrep+brng" -show_frames
    
  • Output specific data about the minimum and maximum values of the Y plane per frame:
    ffprobe -f lavfi movie=example.mov,signalstats -show_entries frame_tags=lavfi.signalstats.YMAX,lavfi.signalstats.YMIN
    
  • Playback video while highlighting pixels that are outside of broadcast range in red.
    ffplay example.mov -vf signalstats="out=brng:color=red"
    
  • Playback video with signalstats metadata drawn over the frame.
    ffplay example.mov -vf signalstats=stat=brng+vrep+tout,drawtext=fontfile=FreeSerif.ttf:textfile=signalstat_drawtext.txt
    

    The contents of signalstat_drawtext.txt used in the command are:

    time %{pts:hms}
    Y (%{metadata:lavfi.signalstats.YMIN}-%{metadata:lavfi.signalstats.YMAX})
    U (%{metadata:lavfi.signalstats.UMIN}-%{metadata:lavfi.signalstats.UMAX})
    V (%{metadata:lavfi.signalstats.VMIN}-%{metadata:lavfi.signalstats.VMAX})
    saturation maximum: %{metadata:lavfi.signalstats.SATMAX}
    
    

9.128 smartblur

Blur the input video without impacting the outlines.

It accepts the following options:

luma_radius, lr

Set the luma radius. The option value must be a float number in the range [0.1,5.0] that specifies the variance of the gaussian filter used to blur the image (slower if larger). Default value is 1.0.

luma_strength, ls

Set the luma strength. The option value must be a float number in the range [-1.0,1.0] that configures the blurring. A value included in [0.0,1.0] will blur the image whereas a value included in [-1.0,0.0] will sharpen the image. Default value is 1.0.

luma_threshold, lt

Set the luma threshold used as a coefficient to determine whether a pixel should be blurred or not. The option value must be an integer in the range [-30,30]. A value of 0 will filter all the image, a value included in [0,30] will filter flat areas and a value included in [-30,0] will filter edges. Default value is 0.

chroma_radius, cr

Set the chroma radius. The option value must be a float number in the range [0.1,5.0] that specifies the variance of the gaussian filter used to blur the image (slower if larger). Default value is 1.0.

chroma_strength, cs

Set the chroma strength. The option value must be a float number in the range [-1.0,1.0] that configures the blurring. A value included in [0.0,1.0] will blur the image whereas a value included in [-1.0,0.0] will sharpen the image. Default value is 1.0.

chroma_threshold, ct

Set the chroma threshold used as a coefficient to determine whether a pixel should be blurred or not. The option value must be an integer in the range [-30,30]. A value of 0 will filter all the image, a value included in [0,30] will filter flat areas and a value included in [-30,0] will filter edges. Default value is 0.

If a chroma option is not explicitly set, the corresponding luma value is set.

9.129 ssim

Obtain the SSIM (Structural SImilarity Metric) between two input videos.

This filter takes in input two input videos, the first input is considered the "main" source and is passed unchanged to the output. The second input is used as a "reference" video for computing the SSIM.

Both video inputs must have the same resolution and pixel format for this filter to work correctly. Also it assumes that both inputs have the same number of frames, which are compared one by one.

The filter stores the calculated SSIM of each frame.

The description of the accepted parameters follows.

stats_file, f

If specified the filter will use the named file to save the SSIM of each individual frame. When filename equals "-" the data is sent to standard output.

The file printed if stats_file is selected, contains a sequence of key/value pairs of the form key:value for each compared couple of frames.

A description of each shown parameter follows:

n

sequential number of the input frame, starting from 1

Y, U, V, R, G, B

SSIM of the compared frames for the component specified by the suffix.

All

SSIM of the compared frames for the whole frame.

dB

Same as above but in dB representation.

For example:

movie=ref_movie.mpg, setpts=PTS-STARTPTS [main];
[main][ref] ssim="stats_file=stats.log" [out]

On this example the input file being processed is compared with the reference file ref_movie.mpg. The SSIM of each individual frame is stored in stats.log.

Another example with both psnr and ssim at same time:

ffmpeg -i main.mpg -i ref.mpg -lavfi  "ssim;[0:v][1:v]psnr" -f null -

9.130 stereo3d

Convert between different stereoscopic image formats.

The filters accept the following options:

in

Set stereoscopic image format of input.

Available values for input image formats are:

sbsl

side by side parallel (left eye left, right eye right)

sbsr

side by side crosseye (right eye left, left eye right)

sbs2l

side by side parallel with half width resolution (left eye left, right eye right)

sbs2r

side by side crosseye with half width resolution (right eye left, left eye right)

abl

above-below (left eye above, right eye below)

abr

above-below (right eye above, left eye below)

ab2l

above-below with half height resolution (left eye above, right eye below)

ab2r

above-below with half height resolution (right eye above, left eye below)

al

alternating frames (left eye first, right eye second)

ar

alternating frames (right eye first, left eye second)

irl

interleaved rows (left eye has top row, right eye starts on next row)

irr

interleaved rows (right eye has top row, left eye starts on next row)

icl

interleaved columns, left eye first

icr

interleaved columns, right eye first

Default value is ‘sbsl’.

out

Set stereoscopic image format of output.

sbsl

side by side parallel (left eye left, right eye right)

sbsr

side by side crosseye (right eye left, left eye right)

sbs2l

side by side parallel with half width resolution (left eye left, right eye right)

sbs2r

side by side crosseye with half width resolution (right eye left, left eye right)

abl

above-below (left eye above, right eye below)

abr

above-below (right eye above, left eye below)

ab2l

above-below with half height resolution (left eye above, right eye below)

ab2r

above-below with half height resolution (right eye above, left eye below)

al

alternating frames (left eye first, right eye second)

ar

alternating frames (right eye first, left eye second)

irl

interleaved rows (left eye has top row, right eye starts on next row)

irr

interleaved rows (right eye has top row, left eye starts on next row)

arbg

anaglyph red/blue gray (red filter on left eye, blue filter on right eye)

argg

anaglyph red/green gray (red filter on left eye, green filter on right eye)

arcg

anaglyph red/cyan gray (red filter on left eye, cyan filter on right eye)

arch

anaglyph red/cyan half colored (red filter on left eye, cyan filter on right eye)

arcc

anaglyph red/cyan color (red filter on left eye, cyan filter on right eye)

arcd

anaglyph red/cyan color optimized with the least squares projection of dubois (red filter on left eye, cyan filter on right eye)

agmg

anaglyph green/magenta gray (green filter on left eye, magenta filter on right eye)

agmh

anaglyph green/magenta half colored (green filter on left eye, magenta filter on right eye)

agmc

anaglyph green/magenta colored (green filter on left eye, magenta filter on right eye)

agmd

anaglyph green/magenta color optimized with the least squares projection of dubois (green filter on left eye, magenta filter on right eye)

aybg

anaglyph yellow/blue gray (yellow filter on left eye, blue filter on right eye)

aybh

anaglyph yellow/blue half colored (yellow filter on left eye, blue filter on right eye)

aybc

anaglyph yellow/blue colored (yellow filter on left eye, blue filter on right eye)

aybd

anaglyph yellow/blue color optimized with the least squares projection of dubois (yellow filter on left eye, blue filter on right eye)

ml

mono output (left eye only)

mr

mono output (right eye only)

chl

checkerboard, left eye first

chr

checkerboard, right eye first

icl

interleaved columns, left eye first

icr

interleaved columns, right eye first

Default value is ‘arcd’.

9.130.1 Examples

  • Convert input video from side by side parallel to anaglyph yellow/blue dubois:
    stereo3d=sbsl:aybd
    
  • Convert input video from above below (left eye above, right eye below) to side by side crosseye.
    stereo3d=abl:sbsr
    

9.131 streamselect, astreamselect

Select video or audio streams.

The filter accepts the following options:

inputs

Set number of inputs. Default is 2.

map

Set input indexes to remap to outputs.

9.131.1 Commands

The streamselect and astreamselect filter supports the following commands:

map

Set input indexes to remap to outputs.

9.131.2 Examples

  • Select first 5 seconds 1st stream and rest of time 2nd stream:
    sendcmd='5.0 streamselect map 1',streamselect=inputs=2:map=0
    
  • Same as above, but for audio:
    asendcmd='5.0 astreamselect map 1',astreamselect=inputs=2:map=0
    

9.132 spp

Apply a simple postprocessing filter that compresses and decompresses the image at several (or - in the case of quality level 6 - all) shifts and average the results.

The filter accepts the following options:

quality

Set quality. This option defines the number of levels for averaging. It accepts an integer in the range 0-6. If set to 0, the filter will have no effect. A value of 6 means the higher quality. For each increment of that value the speed drops by a factor of approximately 2. Default value is 3.

qp

Force a constant quantization parameter. If not set, the filter will use the QP from the video stream (if available).

mode

Set thresholding mode. Available modes are:

hard

Set hard thresholding (default).

soft

Set soft thresholding (better de-ringing effect, but likely blurrier).

use_bframe_qp

Enable the use of the QP from the B-Frames if set to 1. Using this option may cause flicker since the B-Frames have often larger QP. Default is 0 (not enabled).

9.133 subtitles

Draw subtitles on top of input video using the libass library.

To enable compilation of this filter you need to configure FFmpeg with --enable-libass. This filter also requires a build with libavcodec and libavformat to convert the passed subtitles file to ASS (Advanced Substation Alpha) subtitles format.

The filter accepts the following options:

filename, f

Set the filename of the subtitle file to read. It must be specified.

original_size

Specify the size of the original video, the video for which the ASS file was composed. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual. Due to a misdesign in ASS aspect ratio arithmetic, this is necessary to correctly scale the fonts if the aspect ratio has been changed.

fontsdir

Set a directory path containing fonts that can be used by the filter. These fonts will be used in addition to whatever the font provider uses.

charenc

Set subtitles input character encoding. subtitles filter only. Only useful if not UTF-8.

stream_index, si

Set subtitles stream index. subtitles filter only.

force_style

Override default style or script info parameters of the subtitles. It accepts a string containing ASS style format KEY=VALUE couples separated by ",".

If the first key is not specified, it is assumed that the first value specifies the filename.

For example, to render the file sub.srt on top of the input video, use the command:

subtitles=sub.srt

which is equivalent to:

subtitles=filename=sub.srt

To render the default subtitles stream from file video.mkv, use:

subtitles=video.mkv

To render the second subtitles stream from that file, use:

subtitles=video.mkv:si=1

To make the subtitles stream from sub.srt appear in transparent green DejaVu Serif, use:

subtitles=sub.srt:force_style='FontName=DejaVu Serif,PrimaryColour=&HAA00FF00'

9.134 super2xsai

Scale the input by 2x and smooth using the Super2xSaI (Scale and Interpolate) pixel art scaling algorithm.

Useful for enlarging pixel art images without reducing sharpness.

9.135 swaprect

Swap two rectangular objects in video.

This filter accepts the following options:

w

Set object width.

h

Set object height.

x1

Set 1st rect x coordinate.

y1

Set 1st rect y coordinate.

x2

Set 2nd rect x coordinate.

y2

Set 2nd rect y coordinate.

All expressions are evaluated once for each frame.

The all options are expressions containing the following constants:

w
h

The input width and height.

a

same as w / h

sar

input sample aspect ratio

dar

input display aspect ratio, it is the same as (w / h) * sar

n

The number of the input frame, starting from 0.

t

The timestamp expressed in seconds. It’s NAN if the input timestamp is unknown.

pos

the position in the file of the input frame, NAN if unknown

9.136 swapuv

Swap U & V plane.

9.137 telecine

Apply telecine process to the video.

This filter accepts the following options:

first_field
top, t

top field first

bottom, b

bottom field first The default value is top.

pattern

A string of numbers representing the pulldown pattern you wish to apply. The default value is 23.

Some typical patterns:

NTSC output (30i):
27.5p: 32222
24p: 23 (classic)
24p: 2332 (preferred)
20p: 33
18p: 334
16p: 3444

PAL output (25i):
27.5p: 12222
24p: 222222222223 ("Euro pulldown")
16.67p: 33
16p: 33333334

9.138 thumbnail

Select the most representative frame in a given sequence of consecutive frames.

The filter accepts the following options:

n

Set the frames batch size to analyze; in a set of n frames, the filter will pick one of them, and then handle the next batch of n frames until the end. Default is 100.

Since the filter keeps track of the whole frames sequence, a bigger n value will result in a higher memory usage, so a high value is not recommended.

9.138.1 Examples

  • Extract one picture each 50 frames:
    thumbnail=50
    
  • Complete example of a thumbnail creation with ffmpeg:
    ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png
    

9.139 tile

Tile several successive frames together.

The filter accepts the following options:

layout

Set the grid size (i.e. the number of lines and columns). For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual.

nb_frames

Set the maximum number of frames to render in the given area. It must be less than or equal to wxh. The default value is 0, meaning all the area will be used.

margin

Set the outer border margin in pixels.

padding

Set the inner border thickness (i.e. the number of pixels between frames). For more advanced padding options (such as having different values for the edges), refer to the pad video filter.

color

Specify the color of the unused area. For the syntax of this option, check the "Color" section in the ffmpeg-utils manual. The default value of color is "black".

9.139.1 Examples

  • Produce 8x8 PNG tiles of all keyframes (-skip_frame nokey) in a movie:
    ffmpeg -skip_frame nokey -i file.avi -vf 'scale=128:72,tile=8x8' -an -vsync 0 keyframes%03d.png
    

    The -vsync 0 is necessary to prevent ffmpeg from duplicating each output frame to accommodate the originally detected frame rate.

  • Display 5 pictures in an area of 3x2 frames, with 7 pixels between them, and 2 pixels of initial margin, using mixed flat and named options:
    tile=3x2:nb_frames=5:padding=7:margin=2
    

9.140 tinterlace

Perform various types of temporal field interlacing.

Frames are counted starting from 1, so the first input frame is considered odd.

The filter accepts the following options:

mode

Specify the mode of the interlacing. This option can also be specified as a value alone. See below for a list of values for this option.

Available values are:

merge, 0

Move odd frames into the upper field, even into the lower field, generating a double height frame at half frame rate.

 ------> time
Input:
Frame 1         Frame 2         Frame 3         Frame 4

11111           22222           33333           44444
11111           22222           33333           44444
11111           22222           33333           44444
11111           22222           33333           44444

Output:
11111                           33333
22222                           44444
11111                           33333
22222                           44444
11111                           33333
22222                           44444
11111                           33333
22222                           44444
drop_even, 1

Only output odd frames, even frames are dropped, generating a frame with unchanged height at half frame rate.

 ------> time
Input:
Frame 1         Frame 2         Frame 3         Frame 4

11111           22222           33333           44444
11111           22222           33333           44444
11111           22222           33333           44444
11111           22222           33333           44444

Output:
11111                           33333
11111                           33333
11111                           33333
11111                           33333
drop_odd, 2

Only output even frames, odd frames are dropped, generating a frame with unchanged height at half frame rate.

 ------> time
Input:
Frame 1         Frame 2         Frame 3         Frame 4

11111           22222           33333           44444
11111           22222           33333           44444
11111           22222           33333           44444
11111           22222           33333           44444

Output:
                22222                           44444
                22222                           44444
                22222                           44444
                22222                           44444
pad, 3

Expand each frame to full height, but pad alternate lines with black, generating a frame with double height at the same input frame rate.

 ------> time
Input:
Frame 1         Frame 2         Frame 3         Frame 4

11111           22222           33333           44444
11111           22222           33333           44444
11111           22222           33333           44444
11111           22222           33333           44444

Output:
11111           .....           33333           .....
.....           22222           .....           44444
11111           .....           33333           .....
.....           22222           .....           44444
11111           .....           33333           .....
.....           22222           .....           44444
11111           .....           33333           .....
.....           22222           .....           44444
interleave_top, 4

Interleave the upper field from odd frames with the lower field from even frames, generating a frame with unchanged height at half frame rate.

 ------> time
Input:
Frame 1         Frame 2         Frame 3         Frame 4

11111<-         22222           33333<-         44444
11111           22222<-         33333           44444<-
11111<-         22222           33333<-         44444
11111           22222<-         33333           44444<-

Output:
11111                           33333
22222                           44444
11111                           33333
22222                           44444
interleave_bottom, 5

Interleave the lower field from odd frames with the upper field from even frames, generating a frame with unchanged height at half frame rate.

 ------> time
Input:
Frame 1         Frame 2         Frame 3         Frame 4

11111           22222<-         33333           44444<-
11111<-         22222           33333<-         44444
11111           22222<-         33333           44444<-
11111<-         22222           33333<-         44444

Output:
22222                           44444
11111                           33333
22222                           44444
11111                           33333
interlacex2, 6

Double frame rate with unchanged height. Frames are inserted each containing the second temporal field from the previous input frame and the first temporal field from the next input frame. This mode relies on the top_field_first flag. Useful for interlaced video displays with no field synchronisation.

 ------> time
Input:
Frame 1         Frame 2         Frame 3         Frame 4

11111           22222           33333           44444
 11111           22222           33333           44444
11111           22222           33333           44444
 11111           22222           33333           44444

Output:
11111   22222   22222   33333   33333   44444   44444
 11111   11111   22222   22222   33333   33333   44444
11111   22222   22222   33333   33333   44444   44444
 11111   11111   22222   22222   33333   33333   44444
mergex2, 7

Move odd frames into the upper field, even into the lower field, generating a double height frame at same frame rate.

 ------> time
Input:
Frame 1         Frame 2         Frame 3         Frame 4

11111           22222           33333           44444
11111           22222           33333           44444
11111           22222           33333           44444
11111           22222           33333           44444

Output:
11111           33333           33333           55555
22222           22222           44444           44444
11111           33333           33333           55555
22222           22222           44444           44444
11111           33333           33333           55555
22222           22222           44444           44444
11111           33333           33333           55555
22222           22222           44444           44444

Numeric values are deprecated but are accepted for backward compatibility reasons.

Default mode is merge.

flags

Specify flags influencing the filter process.

Available value for flags is:

low_pass_filter, vlfp

Enable vertical low-pass filtering in the filter. Vertical low-pass filtering is required when creating an interlaced destination from a progressive source which contains high-frequency vertical detail. Filtering will reduce interlace ’twitter’ and Moire patterning.

Vertical low-pass filtering can only be enabled for mode interleave_top and interleave_bottom.

9.141 transpose

Transpose rows with columns in the input video and optionally flip it.

It accepts the following parameters:

dir

Specify the transposition direction.

Can assume the following values:

0, 4, cclock_flip

Rotate by 90 degrees counterclockwise and vertically flip (default), that is:

L.R     L.l
. . ->  . .
l.r     R.r
1, 5, clock

Rotate by 90 degrees clockwise, that is:

L.R     l.L
. . ->  . .
l.r     r.R
2, 6, cclock

Rotate by 90 degrees counterclockwise, that is:

L.R     R.r
. . ->  . .
l.r     L.l
3, 7, clock_flip

Rotate by 90 degrees clockwise and vertically flip, that is:

L.R     r.R
. . ->  . .
l.r     l.L

For values between 4-7, the transposition is only done if the input video geometry is portrait and not landscape. These values are deprecated, the passthrough option should be used instead.

Numerical values are deprecated, and should be dropped in favor of symbolic constants.

passthrough

Do not apply the transposition if the input geometry matches the one specified by the specified value. It accepts the following values:

none

Always apply transposition.

portrait

Preserve portrait geometry (when height >= width).

landscape

Preserve landscape geometry (when width >= height).

Default value is none.

For example to rotate by 90 degrees clockwise and preserve portrait layout:

transpose=dir=1:passthrough=portrait

The command above can also be specified as:

transpose=1:portrait

9.142 trim

Trim the input so that the output contains one continuous subpart of the input.

It accepts the following parameters:

start

Specify the time of the start of the kept section, i.e. the frame with the timestamp start will be the first frame in the output.

end

Specify the time of the first frame that will be dropped, i.e. the frame immediately preceding the one with the timestamp end will be the last frame in the output.

start_pts

This is the same as start, except this option sets the start timestamp in timebase units instead of seconds.

end_pts

This is the same as end, except this option sets the end timestamp in timebase units instead of seconds.

duration

The maximum duration of the output in seconds.

start_frame

The number of the first frame that should be passed to the output.

end_frame

The number of the first frame that should be dropped.

start, end, and duration are expressed as time duration specifications; see (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax.

Note that the first two sets of the start/end options and the duration option look at the frame timestamp, while the _frame variants simply count the frames that pass through the filter. Also note that this filter does not modify the timestamps. If you wish for the output timestamps to start at zero, insert a setpts filter after the trim filter.

If multiple start or end options are set, this filter tries to be greedy and keep all the frames that match at least one of the specified constraints. To keep only the part that matches all the constraints at once, chain multiple trim filters.

The defaults are such that all the input is kept. So it is possible to set e.g. just the end values to keep everything before the specified time.

Examples:

  • Drop everything except the second minute of input:
    ffmpeg -i INPUT -vf trim=60:120
    
  • Keep only the first second:
    ffmpeg -i INPUT -vf trim=duration=1
    

9.143 unsharp

Sharpen or blur the input video.

It accepts the following parameters:

luma_msize_x, lx

Set the luma matrix horizontal size. It must be an odd integer between 3 and 63. The default value is 5.

luma_msize_y, ly

Set the luma matrix vertical size. It must be an odd integer between 3 and 63. The default value is 5.

luma_amount, la

Set the luma effect strength. It must be a floating point number, reasonable values lay between -1.5 and 1.5.

Negative values will blur the input video, while positive values will sharpen it, a value of zero will disable the effect.

Default value is 1.0.

chroma_msize_x, cx

Set the chroma matrix horizontal size. It must be an odd integer between 3 and 63. The default value is 5.

chroma_msize_y, cy

Set the chroma matrix vertical size. It must be an odd integer between 3 and 63. The default value is 5.

chroma_amount, ca

Set the chroma effect strength. It must be a floating point number, reasonable values lay between -1.5 and 1.5.

Negative values will blur the input video, while positive values will sharpen it, a value of zero will disable the effect.

Default value is 0.0.

opencl

If set to 1, specify using OpenCL capabilities, only available if FFmpeg was configured with --enable-opencl. Default value is 0.

All parameters are optional and default to the equivalent of the string ’5:5:1.0:5:5:0.0’.

9.143.1 Examples

  • Apply strong luma sharpen effect:
    unsharp=luma_msize_x=7:luma_msize_y=7:luma_amount=2.5
    
  • Apply a strong blur of both luma and chroma parameters:
    unsharp=7:7:-2:7:7:-2
    

9.144 uspp

Apply ultra slow/simple postprocessing filter that compresses and decompresses the image at several (or - in the case of quality level 8 - all) shifts and average the results.

The way this differs from the behavior of spp is that uspp actually encodes & decodes each case with libavcodec Snow, whereas spp uses a simplified intra only 8x8 DCT similar to MJPEG.

The filter accepts the following options:

quality

Set quality. This option defines the number of levels for averaging. It accepts an integer in the range 0-8. If set to 0, the filter will have no effect. A value of 8 means the higher quality. For each increment of that value the speed drops by a factor of approximately 2. Default value is 3.

qp

Force a constant quantization parameter. If not set, the filter will use the QP from the video stream (if available).

9.145 vectorscope

Display 2 color component values in the two dimensional graph (which is called a vectorscope).

This filter accepts the following options:

mode, m

Set vectorscope mode.

It accepts the following values:

gray

Gray values are displayed on graph, higher brightness means more pixels have same component color value on location in graph. This is the default mode.

color

Gray values are displayed on graph. Surrounding pixels values which are not present in video frame are drawn in gradient of 2 color components which are set by option x and y. The 3rd color component is static.

color2

Actual color components values present in video frame are displayed on graph.

color3

Similar as color2 but higher frequency of same values x and y on graph increases value of another color component, which is luminance by default values of x and y.

color4

Actual colors present in video frame are displayed on graph. If two different colors map to same position on graph then color with higher value of component not present in graph is picked.

color5

Gray values are displayed on graph. Similar to color but with 3rd color component picked from radial gradient.

x

Set which color component will be represented on X-axis. Default is 1.

y

Set which color component will be represented on Y-axis. Default is 2.

intensity, i

Set intensity, used by modes: gray, color, color3 and color5 for increasing brightness of color component which represents frequency of (X, Y) location in graph.

envelope, e
none

No envelope, this is default.

instant

Instant envelope, even darkest single pixel will be clearly highlighted.

peak

Hold maximum and minimum values presented in graph over time. This way you can still spot out of range values without constantly looking at vectorscope.

peak+instant

Peak and instant envelope combined together.

graticule, g

Set what kind of graticule to draw.

none
green
color
opacity, o

Set graticule opacity.

flags, f

Set graticule flags.

white

Draw graticule for white point.

black

Draw graticule for black point.

name

Draw color points short names.

bgopacity, b

Set background opacity.

lthreshold, l

Set low threshold for color component not represented on X or Y axis. Values lower than this value will be ignored. Default is 0. Note this value is multiplied with actual max possible value one pixel component can have. So for 8-bit input and low threshold value of 0.1 actual threshold is 0.1 * 255 = 25.

hthreshold, h

Set high threshold for color component not represented on X or Y axis. Values higher than this value will be ignored. Default is 1. Note this value is multiplied with actual max possible value one pixel component can have. So for 8-bit input and high threshold value of 0.9 actual threshold is 0.9 * 255 = 230.

colorspace, c

Set what kind of colorspace to use when drawing graticule.

auto
601
709

Default is auto.

9.146 vidstabdetect

Analyze video stabilization/deshaking. Perform pass 1 of 2, see vidstabtransform for pass 2.

This filter generates a file with relative translation and rotation transform information about subsequent frames, which is then used by the vidstabtransform filter.

To enable compilation of this filter you need to configure FFmpeg with --enable-libvidstab.

This filter accepts the following options:

result

Set the path to the file used to write the transforms information. Default value is transforms.trf.

shakiness

Set how shaky the video is and how quick the camera is. It accepts an integer in the range 1-10, a value of 1 means little shakiness, a value of 10 means strong shakiness. Default value is 5.

accuracy

Set the accuracy of the detection process. It must be a value in the range 1-15. A value of 1 means low accuracy, a value of 15 means high accuracy. Default value is 15.

stepsize

Set stepsize of the search process. The region around minimum is scanned with 1 pixel resolution. Default value is 6.

mincontrast

Set minimum contrast. Below this value a local measurement field is discarded. Must be a floating point value in the range 0-1. Default value is 0.3.

tripod

Set reference frame number for tripod mode.

If enabled, the motion of the frames is compared to a reference frame in the filtered stream, identified by the specified number. The idea is to compensate all movements in a more-or-less static scene and keep the camera view absolutely still.

If set to 0, it is disabled. The frames are counted starting from 1.

show

Show fields and transforms in the resulting frames. It accepts an integer in the range 0-2. Default value is 0, which disables any visualization.

9.146.1 Examples

  • Use default values:
    vidstabdetect
    
  • Analyze strongly shaky movie and put the results in file mytransforms.trf:
    vidstabdetect=shakiness=10:accuracy=15:result="mytransforms.trf"
    
  • Visualize the result of internal transformations in the resulting video:
    vidstabdetect=show=1
    
  • Analyze a video with medium shakiness using ffmpeg:
    ffmpeg -i input -vf vidstabdetect=shakiness=5:show=1 dummy.avi
    

9.147 vidstabtransform

Video stabilization/deshaking: pass 2 of 2, see vidstabdetect for pass 1.

Read a file with transform information for each frame and apply/compensate them. Together with the vidstabdetect filter this can be used to deshake videos. See also http://public.hronopik.de/vid.stab. It is important to also use the unsharp filter, see below.

To enable compilation of this filter you need to configure FFmpeg with --enable-libvidstab.

9.147.1 Options

input

Set path to the file used to read the transforms. Default value is transforms.trf.

smoothing

Set the number of frames (value*2 + 1) used for lowpass filtering the camera movements. Default value is 10.

For example a number of 10 means that 21 frames are used (10 in the past and 10 in the future) to smoothen the motion in the video. A larger value leads to a smoother video, but limits the acceleration of the camera (pan/tilt movements). 0 is a special case where a static camera is simulated.

optalgo

Set the camera path optimization algorithm.

Accepted values are:

gauss

gaussian kernel low-pass filter on camera motion (default)

avg

averaging on transformations

maxshift

Set maximal number of pixels to translate frames. Default value is -1, meaning no limit.

maxangle

Set maximal angle in radians (degree*PI/180) to rotate frames. Default value is -1, meaning no limit.

crop

Specify how to deal with borders that may be visible due to movement compensation.

Available values are:

keep

keep image information from previous frame (default)

black

fill the border black

invert

Invert transforms if set to 1. Default value is 0.

relative

Consider transforms as relative to previous frame if set to 1, absolute if set to 0. Default value is 0.

zoom

Set percentage to zoom. A positive value will result in a zoom-in effect, a negative value in a zoom-out effect. Default value is 0 (no zoom).

optzoom

Set optimal zooming to avoid borders.

Accepted values are:

0

disabled

1

optimal static zoom value is determined (only very strong movements will lead to visible borders) (default)

2

optimal adaptive zoom value is determined (no borders will be visible), see zoomspeed

Note that the value given at zoom is added to the one calculated here.

zoomspeed

Set percent to zoom maximally each frame (enabled when optzoom is set to 2). Range is from 0 to 5, default value is 0.25.

interpol

Specify type of interpolation.

Available values are:

no

no interpolation

linear

linear only horizontal

bilinear

linear in both directions (default)

bicubic

cubic in both directions (slow)

tripod

Enable virtual tripod mode if set to 1, which is equivalent to relative=0:smoothing=0. Default value is 0.

Use also tripod option of vidstabdetect.

debug

Increase log verbosity if set to 1. Also the detected global motions are written to the temporary file global_motions.trf. Default value is 0.

9.147.2 Examples

  • Use ffmpeg for a typical stabilization with default values:
    ffmpeg -i inp.mpeg -vf vidstabtransform,unsharp=5:5:0.8:3:3:0.4 inp_stabilized.mpeg
    

    Note the use of the unsharp filter which is always recommended.

  • Zoom in a bit more and load transform data from a given file:
    vidstabtransform=zoom=5:input="mytransforms.trf"
    
  • Smoothen the video even more:
    vidstabtransform=smoothing=30
    

9.148 vflip

Flip the input video vertically.

For example, to vertically flip a video with ffmpeg:

ffmpeg -i in.avi -vf "vflip" out.avi

9.149 vignette

Make or reverse a natural vignetting effect.

The filter accepts the following options:

angle, a

Set lens angle expression as a number of radians.

The value is clipped in the [0,PI/2] range.

Default value: "PI/5"

x0
y0

Set center coordinates expressions. Respectively "w/2" and "h/2" by default.

mode

Set forward/backward mode.

Available modes are:

forward

The larger the distance from the central point, the darker the image becomes.

backward

The larger the distance from the central point, the brighter the image becomes. This can be used to reverse a vignette effect, though there is no automatic detection to extract the lens angle and other settings (yet). It can also be used to create a burning effect.

Default value is ‘forward’.

eval

Set evaluation mode for the expressions (angle, x0, y0).

It accepts the following values:

init

Evaluate expressions only once during the filter initialization.

frame

Evaluate expressions for each incoming frame. This is way slower than the ‘init’ mode since it requires all the scalers to be re-computed, but it allows advanced dynamic expressions.

Default value is ‘init’.

dither

Set dithering to reduce the circular banding effects. Default is 1 (enabled).

aspect

Set vignette aspect. This setting allows one to adjust the shape of the vignette. Setting this value to the SAR of the input will make a rectangular vignetting following the dimensions of the video.

Default is 1/1.

9.149.1 Expressions

The alpha, x0 and y0 expressions can contain the following parameters.

w
h

input width and height

n

the number of input frame, starting from 0

pts

the PTS (Presentation TimeStamp) time of the filtered video frame, expressed in TB units, NAN if undefined

r

frame rate of the input video, NAN if the input frame rate is unknown

t

the PTS (Presentation TimeStamp) of the filtered video frame, expressed in seconds, NAN if undefined

tb

time base of the input video

9.149.2 Examples

  • Apply simple strong vignetting effect:
    vignette=PI/4
    
  • Make a flickering vignetting:
    vignette='PI/4+random(1)*PI/50':eval=frame
    

9.150 vstack

Stack input videos vertically.

All streams must be of same pixel format and of same width.

Note that this filter is faster than using overlay and pad filter to create same output.

The filter accept the following option:

inputs

Set number of input streams. Default is 2.

shortest

If set to 1, force the output to terminate when the shortest input terminates. Default value is 0.

9.151 w3fdif

Deinterlace the input video ("w3fdif" stands for "Weston 3 Field Deinterlacing Filter").

Based on the process described by Martin Weston for BBC R&D, and implemented based on the de-interlace algorithm written by Jim Easterbrook for BBC R&D, the Weston 3 field deinterlacing filter uses filter coefficients calculated by BBC R&D.

There are two sets of filter coefficients, so called "simple": and "complex". Which set of filter coefficients is used can be set by passing an optional parameter:

filter

Set the interlacing filter coefficients. Accepts one of the following values:

simple

Simple filter coefficient set.

complex

More-complex filter coefficient set.

Default value is ‘complex’.

deint

Specify which frames to deinterlace. Accept one of the following values:

all

Deinterlace all frames,

interlaced

Only deinterlace frames marked as interlaced.

Default value is ‘all’.

9.152 waveform

Video waveform monitor.

The waveform monitor plots color component intensity. By default luminance only. Each column of the waveform corresponds to a column of pixels in the source video.

It accepts the following options:

mode, m

Can be either row, or column. Default is column. In row mode, the graph on the left side represents color component value 0 and the right side represents value = 255. In column mode, the top side represents color component value = 0 and bottom side represents value = 255.

intensity, i

Set intensity. Smaller values are useful to find out how many values of the same luminance are distributed across input rows/columns. Default value is 0.04. Allowed range is [0, 1].

mirror, r

Set mirroring mode. 0 means unmirrored, 1 means mirrored. In mirrored mode, higher values will be represented on the left side for row mode and at the top for column mode. Default is 1 (mirrored).

display, d

Set display mode. It accepts the following values:

overlay

Presents information identical to that in the parade, except that the graphs representing color components are superimposed directly over one another.

This display mode makes it easier to spot relative differences or similarities in overlapping areas of the color components that are supposed to be identical, such as neutral whites, grays, or blacks.

stack

Display separate graph for the color components side by side in row mode or one below the other in column mode.

parade

Display separate graph for the color components side by side in column mode or one below the other in row mode.

Using this display mode makes it easy to spot color casts in the highlights and shadows of an image, by comparing the contours of the top and the bottom graphs of each waveform. Since whites, grays, and blacks are characterized by exactly equal amounts of red, green, and blue, neutral areas of the picture should display three waveforms of roughly equal width/height. If not, the correction is easy to perform by making level adjustments the three waveforms.

Default is stack.

components, c

Set which color components to display. Default is 1, which means only luminance or red color component if input is in RGB colorspace. If is set for example to 7 it will display all 3 (if) available color components.

envelope, e
none

No envelope, this is default.

instant

Instant envelope, minimum and maximum values presented in graph will be easily visible even with small step value.

peak

Hold minimum and maximum values presented in graph across time. This way you can still spot out of range values without constantly looking at waveforms.

peak+instant

Peak and instant envelope combined together.

filter, f
lowpass

No filtering, this is default.

flat

Luma and chroma combined together.

aflat

Similar as above, but shows difference between blue and red chroma.

chroma

Displays only chroma.

color

Displays actual color value on waveform.

acolor

Similar as above, but with luma showing frequency of chroma values.

graticule, g

Set which graticule to display.

none

Do not display graticule.

green

Display green graticule showing legal broadcast ranges.

opacity, o

Set graticule opacity.

flags, fl

Set graticule flags.

numbers

Draw numbers above lines. By default enabled.

dots

Draw dots instead of lines.

scale, s

Set scale used for displaying graticule.

digital
millivolts
ire

Default is digital.

9.153 xbr

Apply the xBR high-quality magnification filter which is designed for pixel art. It follows a set of edge-detection rules, see http://www.libretro.com/forums/viewtopic.php?f=6&t=134.

It accepts the following option:

n

Set the scaling dimension: 2 for 2xBR, 3 for 3xBR and 4 for 4xBR. Default is 3.

9.154 yadif

Deinterlace the input video ("yadif" means "yet another deinterlacing filter").

It accepts the following parameters:

mode

The interlacing mode to adopt. It accepts one of the following values:

0, send_frame

Output one frame for each frame.

1, send_field

Output one frame for each field.

2, send_frame_nospatial

Like send_frame, but it skips the spatial interlacing check.

3, send_field_nospatial

Like send_field, but it skips the spatial interlacing check.

The default value is send_frame.

parity

The picture field parity assumed for the input interlaced video. It accepts one of the following values:

0, tff

Assume the top field is first.

1, bff

Assume the bottom field is first.

-1, auto

Enable automatic detection of field parity.

The default value is auto. If the interlacing is unknown or the decoder does not export this information, top field first will be assumed.

deint

Specify which frames to deinterlace. Accept one of the following values:

0, all

Deinterlace all frames.

1, interlaced

Only deinterlace frames marked as interlaced.

The default value is all.

9.155 zoompan

Apply Zoom & Pan effect.

This filter accepts the following options:

zoom, z

Set the zoom expression. Default is 1.

x
y

Set the x and y expression. Default is 0.

d

Set the duration expression in number of frames. This sets for how many number of frames effect will last for single input image.

s

Set the output image size, default is ’hd720’.

fps

Set the output frame rate, default is ’25’.

Each expression can contain the following constants:

in_w, iw

Input width.

in_h, ih

Input height.

out_w, ow

Output width.

out_h, oh

Output height.

in

Input frame count.

on

Output frame count.

x
y

Last calculated ’x’ and ’y’ position from ’x’ and ’y’ expression for current input frame.

px
py

’x’ and ’y’ of last output frame of previous input frame or 0 when there was not yet such frame (first input frame).

zoom

Last calculated zoom from ’z’ expression for current input frame.

pzoom

Last calculated zoom of last output frame of previous input frame.

duration

Number of output frames for current input frame. Calculated from ’d’ expression for each input frame.

pduration

number of output frames created for previous input frame

a

Rational number: input width / input height

sar

sample aspect ratio

dar

display aspect ratio

9.155.1 Examples

  • Zoom-in up to 1.5 and pan at same time to some spot near center of picture:
    zoompan=z='min(zoom+0.0015,1.5)':d=700:x='if(gte(zoom,1.5),x,x+1/a)':y='if(gte(zoom,1.5),y,y+1)':s=640x360
    
  • Zoom-in up to 1.5 and pan always at center of picture:
    zoompan=z='min(zoom+0.0015,1.5)':d=700:x='iw/2-(iw/zoom/2)':y='ih/2-(ih/zoom/2)'
    

9.156 zscale

Scale (resize) the input video, using the z.lib library: https://github.com/sekrit-twc/zimg.

The zscale filter forces the output display aspect ratio to be the same as the input, by changing the output sample aspect ratio.

If the input image format is different from the format requested by the next filter, the zscale filter will convert the input to the requested format.

9.156.1 Options

The filter accepts the following options.

width, w
height, h

Set the output video dimension expression. Default value is the input dimension.

If the width or w is 0, the input width is used for the output. If the height or h is 0, the input height is used for the output.

If one of the values is -1, the zscale filter will use a value that maintains the aspect ratio of the input image, calculated from the other specified dimension. If both of them are -1, the input size is used

If one of the values is -n with n > 1, the zscale filter will also use a value that maintains the aspect ratio of the input image, calculated from the other specified dimension. After that it will, however, make sure that the calculated dimension is divisible by n and adjust the value if necessary.

See below for the list of accepted constants for use in the dimension expression.

size, s

Set the video size. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual.

dither, d

Set the dither type.

Possible values are:

none
ordered
random
error_diffusion

Default is none.

filter, f

Set the resize filter type.

Possible values are:

point
bilinear
bicubic
spline16
spline36
lanczos

Default is bilinear.

range, r

Set the color range.

Possible values are:

input
limited
full

Default is same as input.

primaries, p

Set the color primaries.

Possible values are:

input
709
unspecified
170m
240m
2020

Default is same as input.

transfer, t

Set the transfer characteristics.

Possible values are:

input
709
unspecified
601
linear
2020_10
2020_12

Default is same as input.

matrix, m

Set the colorspace matrix.

Possible value are:

input
709
unspecified
470bg
170m
2020_ncl
2020_cl

Default is same as input.

rangein, rin

Set the input color range.

Possible values are:

input
limited
full

Default is same as input.

primariesin, pin

Set the input color primaries.

Possible values are:

input
709
unspecified
170m
240m
2020

Default is same as input.

transferin, tin

Set the input transfer characteristics.

Possible values are:

input
709
unspecified
601
linear
2020_10
2020_12

Default is same as input.

matrixin, min

Set the input colorspace matrix.

Possible value are:

input
709
unspecified
470bg
170m
2020_ncl
2020_cl

The values of the w and h options are expressions containing the following constants:

in_w
in_h

The input width and height

iw
ih

These are the same as in_w and in_h.

out_w
out_h

The output (scaled) width and height

ow
oh

These are the same as out_w and out_h

a

The same as iw / ih

sar

input sample aspect ratio

dar

The input display aspect ratio. Calculated from (iw / ih) * sar.

hsub
vsub

horizontal and vertical input chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

ohsub
ovsub

horizontal and vertical output chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.

10 Video Sources

Below is a description of the currently available video sources.

10.1 buffer

Buffer video frames, and make them available to the filter chain.

This source is mainly intended for a programmatic use, in particular through the interface defined in libavfilter/vsrc_buffer.h.

It accepts the following parameters:

video_size

Specify the size (width and height) of the buffered video frames. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual.

width

The input video width.

height

The input video height.

pix_fmt

A string representing the pixel format of the buffered video frames. It may be a number corresponding to a pixel format, or a pixel format name.

time_base

Specify the timebase assumed by the timestamps of the buffered frames.

frame_rate

Specify the frame rate expected for the video stream.

pixel_aspect, sar

The sample (pixel) aspect ratio of the input video.

sws_param

Specify the optional parameters to be used for the scale filter which is automatically inserted when an input change is detected in the input size or format.

hw_frames_ctx

When using a hardware pixel format, this should be a reference to an AVHWFramesContext describing input frames.

For example:

buffer=width=320:height=240:pix_fmt=yuv410p:time_base=1/24:sar=1

will instruct the source to accept video frames with size 320x240 and with format "yuv410p", assuming 1/24 as the timestamps timebase and square pixels (1:1 sample aspect ratio). Since the pixel format with name "yuv410p" corresponds to the number 6 (check the enum AVPixelFormat definition in libavutil/pixfmt.h), this example corresponds to:

buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1

Alternatively, the options can be specified as a flat string, but this syntax is deprecated:

width:height:pix_fmt:time_base.num:time_base.den:pixel_aspect.num:pixel_aspect.den[:sws_param]

10.2 cellauto

Create a pattern generated by an elementary cellular automaton.

The initial state of the cellular automaton can be defined through the filename, and pattern options. If such options are not specified an initial state is created randomly.

At each new frame a new row in the video is filled with the result of the cellular automaton next generation. The behavior when the whole frame is filled is defined by the scroll option.

This source accepts the following options:

filename, f

Read the initial cellular automaton state, i.e. the starting row, from the specified file. In the file, each non-whitespace character is considered an alive cell, a newline will terminate the row, and further characters in the file will be ignored.

pattern, p

Read the initial cellular automaton state, i.e. the starting row, from the specified string.

Each non-whitespace character in the string is considered an alive cell, a newline will terminate the row, and further characters in the string will be ignored.

rate, r

Set the video rate, that is the number of frames generated per second. Default is 25.

random_fill_ratio, ratio

Set the random fill ratio for the initial cellular automaton row. It is a floating point number value ranging from 0 to 1, defaults to 1/PHI.

This option is ignored when a file or a pattern is specified.

random_seed, seed

Set the seed for filling randomly the initial row, must be an integer included between 0 and UINT32_MAX. If not specified, or if explicitly set to -1, the filter will try to use a good random seed on a best effort basis.

rule

Set the cellular automaton rule, it is a number ranging from 0 to 255. Default value is 110.

size, s

Set the size of the output video. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual.

If filename or pattern is specified, the size is set by default to the width of the specified initial state row, and the height is set to width * PHI.

If size is set, it must contain the width of the specified pattern string, and the specified pattern will be centered in the larger row.

If a filename or a pattern string is not specified, the size value defaults to "320x518" (used for a randomly generated initial state).

scroll

If set to 1, scroll the output upward when all the rows in the output have been already filled. If set to 0, the new generated row will be written over the top row just after the bottom row is filled. Defaults to 1.

start_full, full

If set to 1, completely fill the output with generated rows before outputting the first frame. This is the default behavior, for disabling set the value to 0.

stitch

If set to 1, stitch the left and right row edges together. This is the default behavior, for disabling set the value to 0.

10.2.1 Examples

  • Read the initial state from pattern, and specify an output of size 200x400.
    cellauto=f=pattern:s=200x400
    
  • Generate a random initial row with a width of 200 cells, with a fill ratio of 2/3:
    cellauto=ratio=2/3:s=200x200
    
  • Create a pattern generated by rule 18 starting by a single alive cell centered on an initial row with width 100:
    cellauto=p=@:s=100x400:full=0:rule=18
    
  • Specify a more elaborated initial pattern:
    cellauto=p='@@ @ @@':s=100x400:full=0:rule=18
    

10.3 coreimagesrc

Video source generated on GPU using Apple’s CoreImage API on OSX.

This video source is a specialized version of the coreimage video filter. Use a core image generator at the beginning of the applied filterchain to generate the content.

The coreimagesrc video source accepts the following options:

list_generators

List all available generators along with all their respective options as well as possible minimum and maximum values along with the default values.

list_generators=true
size, s

Specify the size of the sourced video. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual. The default value is 320x240.

rate, r

Specify the frame rate of the sourced video, as the number of frames generated per second. It has to be a string in the format frame_rate_num/frame_rate_den, an integer number, a floating point number or a valid video frame rate abbreviation. The default value is "25".

sar

Set the sample aspect ratio of the sourced video.

duration, d

Set the duration of the sourced video. See (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax.

If not specified, or the expressed duration is negative, the video is supposed to be generated forever.

Additionally, all options of the coreimage video filter are accepted. A complete filterchain can be used for further processing of the generated input without CPU-HOST transfer. See coreimage documentation and examples for details.

10.3.1 Examples

  • Use CIQRCodeGenerator to create a QR code for the FFmpeg homepage, given as complete and escaped command-line for Apple’s standard bash shell:
    ffmpeg -f lavfi -i coreimagesrc=s=100x100:filter=CIQRCodeGenerator@inputMessage=https\\\\\://FFmpeg.org/@inputCorrectionLevel=H -frames:v 1 QRCode.png
    

    This example is equivalent to the QRCode example of coreimage without the need for a nullsrc video source.

10.4 mandelbrot

Generate a Mandelbrot set fractal, and progressively zoom towards the point specified with start_x and start_y.

This source accepts the following options:

end_pts

Set the terminal pts value. Default value is 400.

end_scale

Set the terminal scale value. Must be a floating point value. Default value is 0.3.

inner

Set the inner coloring mode, that is the algorithm used to draw the Mandelbrot fractal internal region.

It shall assume one of the following values:

black

Set black mode.

convergence

Show time until convergence.

mincol

Set color based on point closest to the origin of the iterations.

period

Set period mode.

Default value is mincol.

bailout

Set the bailout value. Default value is 10.0.

maxiter

Set the maximum of iterations performed by the rendering algorithm. Default value is 7189.

outer

Set outer coloring mode. It shall assume one of following values:

iteration_count

Set iteration cound mode.

normalized_iteration_count

set normalized iteration count mode.

Default value is normalized_iteration_count.

rate, r

Set frame rate, expressed as number of frames per second. Default value is "25".

size, s

Set frame size. For the syntax of this option, check the "Video size" section in the ffmpeg-utils manual. Default value is "640x480".

start_scale

Set the initial scale value. Default value is 3.0.

start_x

Set the initial x position. Must be a floating point value between -100 and 100. Default value is -0.743643887037158704752191506114774.

start_y

Set the initial y position. Must be a floating point value between -100 and 100. Default value is -0.131825904205311970493132056385139.

10.5 mptestsrc

Generate various test patterns, as generated by the MPlayer test filter.

The size of the generated video is fixed, and is 256x256. This source is useful in particular for testing encoding features.

This source accepts the following options:

rate, r

Specify the frame rate of the sourced video, as the number of frames generated per second. It has to be a string in the format frame_rate_num/frame_rate_den, an integer number, a floating point number or a valid video frame rate abbreviation. The default value is "25".

duration, d

Set the duration of the sourced video. See (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax.

If not specified, or the expressed duration is negative, the video is supposed to be generated forever.

test, t

Set the number or the name of the test to perform. Supported tests are:

dc_luma
dc_chroma
freq_luma
freq_chroma
amp_luma
amp_chroma
cbp
mv
ring1
ring2
all

Default value is "all", which will cycle through the list of all tests.

Some examples:

mptestsrc=t=dc_luma

will generate a "dc_luma" test pattern.

10.6 frei0r_src

Provide a frei0r source.

To enable compilation of this filter you need to install the frei0r header and configure FFmpeg with --enable-frei0r.

This source accepts the following parameters:

size

The size of the video to generate. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual.

framerate

The framerate of the generated video. It may be a string of the form num/den or a frame rate abbreviation.

filter_name

The name to the frei0r source to load. For more information regarding frei0r and how to set the parameters, read the frei0r section in the video filters documentation.

filter_params

A ’|’-separated list of parameters to pass to the frei0r source.

For example, to generate a frei0r partik0l source with size 200x200 and frame rate 10 which is overlaid on the overlay filter main input:

frei0r_src=size=200x200:framerate=10:filter_name=partik0l:filter_params=1234 [overlay]; [in][overlay] overlay

10.7 life

Generate a life pattern.

This source is based on a generalization of John Conway’s life game.

The sourced input represents a life grid, each pixel represents a cell which can be in one of two possible states, alive or dead. Every cell interacts with its eight neighbours, which are the cells that are horizontally, vertically, or diagonally adjacent.

At each interaction the grid evolves according to the adopted rule, which specifies the number of neighbor alive cells which will make a cell stay alive or born. The rule option allows one to specify the rule to adopt.

This source accepts the following options:

filename, f

Set the file from which to read the initial grid state. In the file, each non-whitespace character is considered an alive cell, and newline is used to delimit the end of each row.

If this option is not specified, the initial grid is generated randomly.

rate, r

Set the video rate, that is the number of frames generated per second. Default is 25.

random_fill_ratio, ratio

Set the random fill ratio for the initial random grid. It is a floating point number value ranging from 0 to 1, defaults to 1/PHI. It is ignored when a file is specified.

random_seed, seed

Set the seed for filling the initial random grid, must be an integer included between 0 and UINT32_MAX. If not specified, or if explicitly set to -1, the filter will try to use a good random seed on a best effort basis.

rule

Set the life rule.

A rule can be specified with a code of the kind "SNS/BNB", where NS and NB are sequences of numbers in the range 0-8, NS specifies the number of alive neighbor cells which make a live cell stay alive, and NB the number of alive neighbor cells which make a dead cell to become alive (i.e. to "born"). "s" and "b" can be used in place of "S" and "B", respectively.

Alternatively a rule can be specified by an 18-bits integer. The 9 high order bits are used to encode the next cell state if it is alive for each number of neighbor alive cells, the low order bits specify the rule for "borning" new cells. Higher order bits encode for an higher number of neighbor cells. For example the number 6153 = (12<<9)+9 specifies a stay alive rule of 12 and a born rule of 9, which corresponds to "S23/B03".

Default value is "S23/B3", which is the original Conway’s game of life rule, and will keep a cell alive if it has 2 or 3 neighbor alive cells, and will born a new cell if there are three alive cells around a dead cell.

size, s

Set the size of the output video. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual.

If filename is specified, the size is set by default to the same size of the input file. If size is set, it must contain the size specified in the input file, and the initial grid defined in that file is centered in the larger resulting area.

If a filename is not specified, the size value defaults to "320x240" (used for a randomly generated initial grid).

stitch

If set to 1, stitch the left and right grid edges together, and the top and bottom edges also. Defaults to 1.

mold

Set cell mold speed. If set, a dead cell will go from death_color to mold_color with a step of mold. mold can have a value from 0 to 255.

life_color

Set the color of living (or new born) cells.

death_color

Set the color of dead cells. If mold is set, this is the first color used to represent a dead cell.

mold_color

Set mold color, for definitely dead and moldy cells.

For the syntax of these 3 color options, check the "Color" section in the ffmpeg-utils manual.

10.7.1 Examples

  • Read a grid from pattern, and center it on a grid of size 300x300 pixels:
    life=f=pattern:s=300x300
    
  • Generate a random grid of size 200x200, with a fill ratio of 2/3:
    life=ratio=2/3:s=200x200
    
  • Specify a custom rule for evolving a randomly generated grid:
    life=rule=S14/B34
    
  • Full example with slow death effect (mold) using ffplay:
    ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_color=#00ff00,scale=1200:800:flags=16
    

10.8 allrgb, allyuv, color, haldclutsrc, nullsrc, rgbtestsrc, smptebars, smptehdbars, testsrc, testsrc2

The allrgb source returns frames of size 4096x4096 of all rgb colors.

The allyuv source returns frames of size 4096x4096 of all yuv colors.

The color source provides an uniformly colored input.

The haldclutsrc source provides an identity Hald CLUT. See also haldclut filter.

The nullsrc source returns unprocessed video frames. It is mainly useful to be employed in analysis / debugging tools, or as the source for filters which ignore the input data.

The rgbtestsrc source generates an RGB test pattern useful for detecting RGB vs BGR issues. You should see a red, green and blue stripe from top to bottom.

The smptebars source generates a color bars pattern, based on the SMPTE Engineering Guideline EG 1-1990.

The smptehdbars source generates a color bars pattern, based on the SMPTE RP 219-2002.

The testsrc source generates a test video pattern, showing a color pattern, a scrolling gradient and a timestamp. This is mainly intended for testing purposes.

The testsrc2 source is similar to testsrc, but supports more pixel formats instead of just rgb24. This allows using it as an input for other tests without requiring a format conversion.

The sources accept the following parameters:

color, c

Specify the color of the source, only available in the color source. For the syntax of this option, check the "Color" section in the ffmpeg-utils manual.

level

Specify the level of the Hald CLUT, only available in the haldclutsrc source. A level of N generates a picture of N*N*N by N*N*N pixels to be used as identity matrix for 3D lookup tables. Each component is coded on a 1/(N*N) scale.

size, s

Specify the size of the sourced video. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual. The default value is 320x240.

This option is not available with the haldclutsrc filter.

rate, r

Specify the frame rate of the sourced video, as the number of frames generated per second. It has to be a string in the format frame_rate_num/frame_rate_den, an integer number, a floating point number or a valid video frame rate abbreviation. The default value is "25".

sar

Set the sample aspect ratio of the sourced video.

duration, d

Set the duration of the sourced video. See (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax.

If not specified, or the expressed duration is negative, the video is supposed to be generated forever.

decimals, n

Set the number of decimals to show in the timestamp, only available in the testsrc source.

The displayed timestamp value will correspond to the original timestamp value multiplied by the power of 10 of the specified value. Default value is 0.

For example the following:

testsrc=duration=5.3:size=qcif:rate=10

will generate a video with a duration of 5.3 seconds, with size 176x144 and a frame rate of 10 frames per second.

The following graph description will generate a red source with an opacity of 0.2, with size "qcif" and a frame rate of 10 frames per second.

color=c=red@0.2:s=qcif:r=10

If the input content is to be ignored, nullsrc can be used. The following command generates noise in the luminance plane by employing the geq filter:

nullsrc=s=256x256, geq=random(1)*255:128:128

10.8.1 Commands

The color source supports the following commands:

c, color

Set the color of the created image. Accepts the same syntax of the corresponding color option.

11 Video Sinks

Below is a description of the currently available video sinks.

11.1 buffersink

Buffer video frames, and make them available to the end of the filter graph.

This sink is mainly intended for programmatic use, in particular through the interface defined in libavfilter/buffersink.h or the options system.

It accepts a pointer to an AVBufferSinkContext structure, which defines the incoming buffers’ formats, to be passed as the opaque parameter to avfilter_init_filter for initialization.

11.2 nullsink

Null video sink: do absolutely nothing with the input video. It is mainly useful as a template and for use in analysis / debugging tools.

12 Multimedia Filters

Below is a description of the currently available multimedia filters.

12.1 ahistogram

Convert input audio to a video output, displaying the volume histogram.

The filter accepts the following options:

dmode

Specify how histogram is calculated.

It accepts the following values:

single

Use single histogram for all channels.

separate

Use separate histogram for each channel.

Default is single.

rate, r

Set frame rate, expressed as number of frames per second. Default value is "25".

size, s

Specify the video size for the output. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual. Default value is hd720.

scale

Set display scale.

It accepts the following values:

log

logarithmic

sqrt

square root

cbrt

cubic root

lin

linear

rlog

reverse logarithmic

Default is log.

ascale

Set amplitude scale.

It accepts the following values:

log

logarithmic

lin

linear

Default is log.

acount

Set how much frames to accumulate in histogram. Defauls is 1. Setting this to -1 accumulates all frames.

rheight

Set histogram ratio of window height.

slide

Set sonogram sliding.

It accepts the following values:

replace

replace old rows with new ones.

scroll

scroll from top to bottom.

Default is replace.

12.2 aphasemeter

Convert input audio to a video output, displaying the audio phase.

The filter accepts the following options:

rate, r

Set the output frame rate. Default value is 25.

size, s

Set the video size for the output. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual. Default value is 800x400.

rc
gc
bc

Specify the red, green, blue contrast. Default values are 2, 7 and 1. Allowed range is [0, 255].

mpc

Set color which will be used for drawing median phase. If color is none which is default, no median phase value will be drawn.

The filter also exports the frame metadata lavfi.aphasemeter.phase which represents mean phase of current audio frame. Value is in range [-1, 1]. The -1 means left and right channels are completely out of phase and 1 means channels are in phase.

12.3 avectorscope

Convert input audio to a video output, representing the audio vector scope.

The filter is used to measure the difference between channels of stereo audio stream. A monoaural signal, consisting of identical left and right signal, results in straight vertical line. Any stereo separation is visible as a deviation from this line, creating a Lissajous figure. If the straight (or deviation from it) but horizontal line appears this indicates that the left and right channels are out of phase.

The filter accepts the following options:

mode, m

Set the vectorscope mode.

Available values are:

lissajous

Lissajous rotated by 45 degrees.

lissajous_xy

Same as above but not rotated.

polar

Shape resembling half of circle.

Default value is ‘lissajous’.

size, s

Set the video size for the output. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual. Default value is 400x400.

rate, r

Set the output frame rate. Default value is 25.

rc
gc
bc
ac

Specify the red, green, blue and alpha contrast. Default values are 40, 160, 80 and 255. Allowed range is [0, 255].

rf
gf
bf
af

Specify the red, green, blue and alpha fade. Default values are 15, 10, 5 and 5. Allowed range is [0, 255].

zoom

Set the zoom factor. Default value is 1. Allowed range is [1, 10].

draw

Set the vectorscope drawing mode.

Available values are:

dot

Draw dot for each sample.

line

Draw line between previous and current sample.

Default value is ‘dot’.

12.3.1 Examples

  • Complete example using ffplay:
    ffplay -f lavfi 'amovie=input.mp3, asplit [a][out1];
                 [a] avectorscope=zoom=1.3:rc=2:gc=200:bc=10:rf=1:gf=8:bf=7 [out0]'
    

12.4 bench, abench

Benchmark part of a filtergraph.

The filter accepts the following options:

action

Start or stop a timer.

Available values are:

start

Get the current time, set it as frame metadata (using the key lavfi.bench.start_time), and forward the frame to the next filter.

stop

Get the current time and fetch the lavfi.bench.start_time metadata from the input frame metadata to get the time difference. Time difference, average, maximum and minimum time (respectively t, avg, max and min) are then printed. The timestamps are expressed in seconds.

12.4.1 Examples

  • Benchmark selectivecolor filter:
    bench=start,selectivecolor=reds=-.2 .12 -.49,bench=stop
    

12.5 concat

Concatenate audio and video streams, joining them together one after the other.

The filter works on segments of synchronized video and audio streams. All segments must have the same number of streams of each type, and that will also be the number of streams at output.

The filter accepts the following options:

n

Set the number of segments. Default is 2.

v

Set the number of output video streams, that is also the number of video streams in each segment. Default is 1.

a

Set the number of output audio streams, that is also the number of audio streams in each segment. Default is 0.

unsafe

Activate unsafe mode: do not fail if segments have a different format.

The filter has v+a outputs: first v video outputs, then a audio outputs.

There are nx(v+a) inputs: first the inputs for the first segment, in the same order as the outputs, then the inputs for the second segment, etc.

Related streams do not always have exactly the same duration, for various reasons including codec frame size or sloppy authoring. For that reason, related synchronized streams (e.g. a video and its audio track) should be concatenated at once. The concat filter will use the duration of the longest stream in each segment (except the last one), and if necessary pad shorter audio streams with silence.

For this filter to work correctly, all segments must start at timestamp 0.

All corresponding streams must have the same parameters in all segments; the filtering system will automatically select a common pixel format for video streams, and a common sample format, sample rate and channel layout for audio streams, but other settings, such as resolution, must be converted explicitly by the user.

Different frame rates are acceptable but will result in variable frame rate at output; be sure to configure the output file to handle it.

12.5.1 Examples

  • Concatenate an opening, an episode and an ending, all in bilingual version (video in stream 0, audio in streams 1 and 2):
    ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv -filter_complex \
      '[0:0] [0:1] [0:2] [1:0] [1:1] [1:2] [2:0] [2:1] [2:2]
       concat=n=3:v=1:a=2 [v] [a1] [a2]' \
      -map '[v]' -map '[a1]' -map '[a2]' output.mkv
    
  • Concatenate two parts, handling audio and video separately, using the (a)movie sources, and adjusting the resolution:
    movie=part1.mp4, scale=512:288 [v1] ; amovie=part1.mp4 [a1] ;
    movie=part2.mp4, scale=512:288 [v2] ; amovie=part2.mp4 [a2] ;
    [v1] [v2] concat [outv] ; [a1] [a2] concat=v=0:a=1 [outa]
    

    Note that a desync will happen at the stitch if the audio and video streams do not have exactly the same duration in the first file.

12.6 ebur128

EBU R128 scanner filter. This filter takes an audio stream as input and outputs it unchanged. By default, it logs a message at a frequency of 10Hz with the Momentary loudness (identified by M), Short-term loudness (S), Integrated loudness (I) and Loudness Range (LRA).

The filter also has a video output (see the video option) with a real time graph to observe the loudness evolution. The graphic contains the logged message mentioned above, so it is not printed anymore when this option is set, unless the verbose logging is set. The main graphing area contains the short-term loudness (3 seconds of analysis), and the gauge on the right is for the momentary loudness (400 milliseconds).

More information about the Loudness Recommendation EBU R128 on http://tech.ebu.ch/loudness.

The filter accepts the following options:

video

Activate the video output. The audio stream is passed unchanged whether this option is set or no. The video stream will be the first output stream if activated. Default is 0.

size

Set the video size. This option is for video only. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual. Default and minimum resolution is 640x480.

meter

Set the EBU scale meter. Default is 9. Common values are 9 and 18, respectively for EBU scale meter +9 and EBU scale meter +18. Any other integer value between this range is allowed.

metadata

Set metadata injection. If set to 1, the audio input will be segmented into 100ms output frames, each of them containing various loudness information in metadata. All the metadata keys are prefixed with lavfi.r128..

Default is 0.

framelog

Force the frame logging level.

Available values are:

info

information logging level

verbose

verbose logging level

By default, the logging level is set to info. If the video or the metadata options are set, it switches to verbose.

peak

Set peak mode(s).

Available modes can be cumulated (the option is a flag type). Possible values are:

none

Disable any peak mode (default).

sample

Enable sample-peak mode.

Simple peak mode looking for the higher sample value. It logs a message for sample-peak (identified by SPK).

true

Enable true-peak mode.

If enabled, the peak lookup is done on an over-sampled version of the input stream for better peak accuracy. It logs a message for true-peak. (identified by TPK) and true-peak per frame (identified by FTPK). This mode requires a build with libswresample.

dualmono

Treat mono input files as "dual mono". If a mono file is intended for playback on a stereo system, its EBU R128 measurement will be perceptually incorrect. If set to true, this option will compensate for this effect. Multi-channel input files are not affected by this option.

panlaw

Set a specific pan law to be used for the measurement of dual mono files. This parameter is optional, and has a default value of -3.01dB.

12.6.1 Examples

  • Real-time graph using ffplay, with a EBU scale meter +18:
    ffplay -f lavfi -i "amovie=input.mp3,ebur128=video=1:meter=18 [out0][out1]"
    
  • Run an analysis with ffmpeg:
    ffmpeg -nostats -i input.mp3 -filter_complex ebur128 -f null -
    

12.7 interleave, ainterleave

Temporally interleave frames from several inputs.

interleave works with video inputs, ainterleave with audio.

These filters read frames from several inputs and send the oldest queued frame to the output.

Input streams must have a well defined, monotonically increasing frame timestamp values.

In order to submit one frame to output, these filters need to enqueue at least one frame for each input, so they cannot work in case one input is not yet terminated and will not receive incoming frames.

For example consider the case when one input is a select filter which always drop input frames. The interleave filter will keep reading from that input, but it will never be able to send new frames to output until the input will send an end-of-stream signal.

Also, depending on inputs synchronization, the filters will drop frames in case one input receives more frames than the other ones, and the queue is already filled.

These filters accept the following options:

nb_inputs, n

Set the number of different inputs, it is 2 by default.

12.7.1 Examples

  • Interleave frames belonging to different streams using ffmpeg:
    ffmpeg -i bambi.avi -i pr0n.mkv -filter_complex "[0:v][1:v] interleave" out.avi
    
  • Add flickering blur effect:
    select='if(gt(random(0), 0.2), 1, 2)':n=2 [tmp], boxblur=2:2, [tmp] interleave
    

12.8 perms, aperms

Set read/write permissions for the output frames.

These filters are mainly aimed at developers to test direct path in the following filter in the filtergraph.

The filters accept the following options:

mode

Select the permissions mode.

It accepts the following values:

none

Do nothing. This is the default.

ro

Set all the output frames read-only.

rw

Set all the output frames directly writable.

toggle

Make the frame read-only if writable, and writable if read-only.

random

Set each output frame read-only or writable randomly.

seed

Set the seed for the random mode, must be an integer included between 0 and UINT32_MAX. If not specified, or if explicitly set to -1, the filter will try to use a good random seed on a best effort basis.

Note: in case of auto-inserted filter between the permission filter and the following one, the permission might not be received as expected in that following filter. Inserting a format or aformat filter before the perms/aperms filter can avoid this problem.

12.9 realtime, arealtime

Slow down filtering to match real time approximatively.

These filters will pause the filtering for a variable amount of time to match the output rate with the input timestamps. They are similar to the re option to ffmpeg.

They accept the following options:

limit

Time limit for the pauses. Any pause longer than that will be considered a timestamp discontinuity and reset the timer. Default is 2 seconds.

12.10 select, aselect

Select frames to pass in output.

This filter accepts the following options:

expr, e

Set expression, which is evaluated for each input frame.

If the expression is evaluated to zero, the frame is discarded.

If the evaluation result is negative or NaN, the frame is sent to the first output; otherwise it is sent to the output with index ceil(val)-1, assuming that the input index starts from 0.

For example a value of 1.2 corresponds to the output with index ceil(1.2)-1 = 2-1 = 1, that is the second output.

outputs, n

Set the number of outputs. The output to which to send the selected frame is based on the result of the evaluation. Default value is 1.

The expression can contain the following constants:

n

The (sequential) number of the filtered frame, starting from 0.

selected_n

The (sequential) number of the selected frame, starting from 0.

prev_selected_n

The sequential number of the last selected frame. It’s NAN if undefined.

TB

The timebase of the input timestamps.

pts

The PTS (Presentation TimeStamp) of the filtered video frame, expressed in TB units. It’s NAN if undefined.

t

The PTS of the filtered video frame, expressed in seconds. It’s NAN if undefined.

prev_pts

The PTS of the previously filtered video frame. It’s NAN if undefined.

prev_selected_pts

The PTS of the last previously filtered video frame. It’s NAN if undefined.

prev_selected_t

The PTS of the last previously selected video frame. It’s NAN if undefined.

start_pts

The PTS of the first video frame in the video. It’s NAN if undefined.

start_t

The time of the first video frame in the video. It’s NAN if undefined.

pict_type (video only)

The type of the filtered frame. It can assume one of the following values:

I
P
B
S
SI
SP
BI
interlace_type (video only)

The frame interlace type. It can assume one of the following values:

PROGRESSIVE

The frame is progressive (not interlaced).

TOPFIRST

The frame is top-field-first.

BOTTOMFIRST

The frame is bottom-field-first.

consumed_sample_n (audio only)

the number of selected samples before the current frame

samples_n (audio only)

the number of samples in the current frame

sample_rate (audio only)

the input sample rate

key

This is 1 if the filtered frame is a key-frame, 0 otherwise.

pos

the position in the file of the filtered frame, -1 if the information is not available (e.g. for synthetic video)

scene (video only)

value between 0 and 1 to indicate a new scene; a low value reflects a low probability for the current frame to introduce a new scene, while a higher value means the current frame is more likely to be one (see the example below)

concatdec_select

The concat demuxer can select only part of a concat input file by setting an inpoint and an outpoint, but the output packets may not be entirely contained in the selected interval. By using this variable, it is possible to skip frames generated by the concat demuxer which are not exactly contained in the selected interval.

This works by comparing the frame pts against the lavf.concat.start_time and the lavf.concat.duration packet metadata values which are also present in the decoded frames.

The concatdec_select variable is -1 if the frame pts is at least start_time and either the duration metadata is missing or the frame pts is less than start_time + duration, 0 otherwise, and NaN if the start_time metadata is missing.

That basically means that an input frame is selected if its pts is within the interval set by the concat demuxer.

The default value of the select expression is "1".

12.10.1 Examples

  • Select all frames in input:
    select
    

    The example above is the same as:

    select=1
    
  • Skip all frames:
    select=0
    
  • Select only I-frames:
    select='eq(pict_type\,I)'
    
  • Select one frame every 100:
    select='not(mod(n\,100))'
    
  • Select only frames contained in the 10-20 time interval:
    select=between(t\,10\,20)
    
  • Select only I-frames contained in the 10-20 time interval:
    select=between(t\,10\,20)*eq(pict_type\,I)
    
  • Select frames with a minimum distance of 10 seconds:
    select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
    
  • Use aselect to select only audio frames with samples number > 100:
    aselect='gt(samples_n\,100)'
    
  • Create a mosaic of the first scenes:
    ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png
    

    Comparing scene against a value between 0.3 and 0.5 is generally a sane choice.

  • Send even and odd frames to separate outputs, and compose them:
    select=n=2:e='mod(n, 2)+1' [odd][even]; [odd] pad=h=2*ih [tmp]; [tmp][even] overlay=y=h
    
  • Select useful frames from an ffconcat file which is using inpoints and outpoints but where the source files are not intra frame only.
    ffmpeg -copyts -vsync 0 -segment_time_metadata 1 -i input.ffconcat -vf select=concatdec_select -af aselect=concatdec_select output.avi
    

12.11 sendcmd, asendcmd

Send commands to filters in the filtergraph.

These filters read commands to be sent to other filters in the filtergraph.

sendcmd must be inserted between two video filters, asendcmd must be inserted between two audio filters, but apart from that they act the same way.

The specification of commands can be provided in the filter arguments with the commands option, or in a file specified by the filename option.

These filters accept the following options:

commands, c

Set the commands to be read and sent to the other filters.

filename, f

Set the filename of the commands to be read and sent to the other filters.

12.11.1 Commands syntax

A commands description consists of a sequence of interval specifications, comprising a list of commands to be executed when a particular event related to that interval occurs. The occurring event is typically the current frame time entering or leaving a given time interval.

An interval is specified by the following syntax:

START[-END] COMMANDS;

The time interval is specified by the START and END times. END is optional and defaults to the maximum time.

The current frame time is considered within the specified interval if it is included in the interval [START, END), that is when the time is greater or equal to START and is lesser than END.

COMMANDS consists of a sequence of one or more command specifications, separated by ",", relating to that interval. The syntax of a command specification is given by:

[FLAGS] TARGET COMMAND ARG

FLAGS is optional and specifies the type of events relating to the time interval which enable sending the specified command, and must be a non-null sequence of identifier flags separated by "+" or "|" and enclosed between "[" and "]".

The following flags are recognized:

enter

The command is sent when the current frame timestamp enters the specified interval. In other words, the command is sent when the previous frame timestamp was not in the given interval, and the current is.

leave

The command is sent when the current frame timestamp leaves the specified interval. In other words, the command is sent when the previous frame timestamp was in the given interval, and the current is not.

If FLAGS is not specified, a default value of [enter] is assumed.

TARGET specifies the target of the command, usually the name of the filter class or a specific filter instance name.

COMMAND specifies the name of the command for the target filter.

ARG is optional and specifies the optional list of argument for the given COMMAND.

Between one interval specification and another, whitespaces, or sequences of characters starting with # until the end of line, are ignored and can be used to annotate comments.

A simplified BNF description of the commands specification syntax follows:

COMMAND_FLAG  ::= "enter" | "leave"
COMMAND_FLAGS ::= COMMAND_FLAG [(+|"|")COMMAND_FLAG]
COMMAND       ::= ["[" COMMAND_FLAGS "]"] TARGET COMMAND [ARG]
COMMANDS      ::= COMMAND [,COMMANDS]
INTERVAL      ::= START[-END] COMMANDS
INTERVALS     ::= INTERVAL[;INTERVALS]

12.11.2 Examples

  • Specify audio tempo change at second 4:
    asendcmd=c='4.0 atempo tempo 1.5',atempo
    
  • Specify a list of drawtext and hue commands in a file.
    # show text in the interval 5-10
    5.0-10.0 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=hello world',
             [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=';
    
    # desaturate the image in the interval 15-20
    15.0-20.0 [enter] hue s 0,
              [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=nocolor',
              [leave] hue s 1,
              [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=color';
    
    # apply an exponential saturation fade-out effect, starting from time 25
    25 [enter] hue s exp(25-t)
    

    A filtergraph allowing to read and process the above command list stored in a file test.cmd, can be specified with:

    sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='',hue
    

12.12 setpts, asetpts

Change the PTS (presentation timestamp) of the input frames.

setpts works on video frames, asetpts on audio frames.

This filter accepts the following options:

expr

The expression which is evaluated for each frame to construct its timestamp.

The expression is evaluated through the eval API and can contain the following constants:

FRAME_RATE

frame rate, only defined for constant frame-rate video

PTS

The presentation timestamp in input

N

The count of the input frame for video or the number of consumed samples, not including the current frame for audio, starting from 0.

NB_CONSUMED_SAMPLES

The number of consumed samples, not including the current frame (only audio)

NB_SAMPLES, S

The number of samples in the current frame (only audio)

SAMPLE_RATE, SR

The audio sample rate.

STARTPTS

The PTS of the first frame.

STARTT

the time in seconds of the first frame

INTERLACED

State whether the current frame is interlaced.

T

the time in seconds of the current frame

POS

original position in the file of the frame, or undefined if undefined for the current frame

PREV_INPTS

The previous input PTS.

PREV_INT

previous input time in seconds

PREV_OUTPTS

The previous output PTS.

PREV_OUTT

previous output time in seconds

RTCTIME

The wallclock (RTC) time in microseconds. This is deprecated, use time(0) instead.

RTCSTART

The wallclock (RTC) time at the start of the movie in microseconds.

TB

The timebase of the input timestamps.

12.12.1 Examples

  • Start counting PTS from zero
    setpts=PTS-STARTPTS
    
  • Apply fast motion effect:
    setpts=0.5*PTS
    
  • Apply slow motion effect:
    setpts=2.0*PTS
    
  • Set fixed rate of 25 frames per second:
    setpts=N/(25*TB)
    
  • Set fixed rate 25 fps with some jitter:
    setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
    
  • Apply an offset of 10 seconds to the input PTS:
    setpts=PTS+10/TB
    
  • Generate timestamps from a "live source" and rebase onto the current timebase:
    setpts='(RTCTIME - RTCSTART) / (TB * 1000000)'
    
  • Generate timestamps by counting samples:
    asetpts=N/SR/TB
    

12.13 settb, asettb

Set the timebase to use for the output frames timestamps. It is mainly useful for testing timebase configuration.

It accepts the following parameters:

expr, tb

The expression which is evaluated into the output timebase.

The value for tb is an arithmetic expression representing a rational. The expression can contain the constants "AVTB" (the default timebase), "intb" (the input timebase) and "sr" (the sample rate, audio only). Default value is "intb".

12.13.1 Examples

  • Set the timebase to 1/25:
    settb=expr=1/25
    
  • Set the timebase to 1/10:
    settb=expr=0.1
    
  • Set the timebase to 1001/1000:
    settb=1+0.001
    
  • Set the timebase to 2*intb:
    settb=2*intb
    
  • Set the default timebase value:
    settb=AVTB
    

12.14 showcqt

Convert input audio to a video output representing frequency spectrum logarithmically using Brown-Puckette constant Q transform algorithm with direct frequency domain coefficient calculation (but the transform itself is not really constant Q, instead the Q factor is actually variable/clamped), with musical tone scale, from E0 to D#10.

The filter accepts the following options:

size, s

Specify the video size for the output. It must be even. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual. Default value is 1920x1080.

fps, rate, r

Set the output frame rate. Default value is 25.

bar_h

Set the bargraph height. It must be even. Default value is -1 which computes the bargraph height automatically.

axis_h

Set the axis height. It must be even. Default value is -1 which computes the axis height automatically.

sono_h

Set the sonogram height. It must be even. Default value is -1 which computes the sonogram height automatically.

fullhd

Set the fullhd resolution. This option is deprecated, use size, s instead. Default value is 1.

sono_v, volume

Specify the sonogram volume expression. It can contain variables:

bar_v

the bar_v evaluated expression

frequency, freq, f

the frequency where it is evaluated

timeclamp, tc

the value of timeclamp option

and functions:

a_weighting(f)

A-weighting of equal loudness

b_weighting(f)

B-weighting of equal loudness

c_weighting(f)

C-weighting of equal loudness.

Default value is 16.

bar_v, volume2

Specify the bargraph volume expression. It can contain variables:

sono_v

the sono_v evaluated expression

frequency, freq, f

the frequency where it is evaluated

timeclamp, tc

the value of timeclamp option

and functions:

a_weighting(f)

A-weighting of equal loudness

b_weighting(f)

B-weighting of equal loudness

c_weighting(f)

C-weighting of equal loudness.

Default value is sono_v.

sono_g, gamma

Specify the sonogram gamma. Lower gamma makes the spectrum more contrast, higher gamma makes the spectrum having more range. Default value is 3. Acceptable range is [1, 7].

bar_g, gamma2

Specify the bargraph gamma. Default value is 1. Acceptable range is [1, 7].

timeclamp, tc

Specify the transform timeclamp. At low frequency, there is trade-off between accuracy in time domain and frequency domain. If timeclamp is lower, event in time domain is represented more accurately (such as fast bass drum), otherwise event in frequency domain is represented more accurately (such as bass guitar). Acceptable range is [0.1, 1]. Default value is 0.17.

basefreq

Specify the transform base frequency. Default value is 20.01523126408007475, which is frequency 50 cents below E0. Acceptable range is [10, 100000].

endfreq

Specify the transform end frequency. Default value is 20495.59681441799654, which is frequency 50 cents above D#10. Acceptable range is [10, 100000].

coeffclamp

This option is deprecated and ignored.

tlength

Specify the transform length in time domain. Use this option to control accuracy trade-off between time domain and frequency domain at every frequency sample. It can contain variables:

frequency, freq, f

the frequency where it is evaluated

timeclamp, tc

the value of timeclamp option.

Default value is 384*tc/(384+tc*f).

count

Specify the transform count for every video frame. Default value is 6. Acceptable range is [1, 30].

fcount

Specify the transform count for every single pixel. Default value is 0, which makes it computed automatically. Acceptable range is [0, 10].

fontfile

Specify font file for use with freetype to draw the axis. If not specified, use embedded font. Note that drawing with font file or embedded font is not implemented with custom basefreq and endfreq, use axisfile option instead.

fontcolor

Specify font color expression. This is arithmetic expression that should return integer value 0xRRGGBB. It can contain variables:

frequency, freq, f

the frequency where it is evaluated

timeclamp, tc

the value of timeclamp option

and functions:

midi(f)

midi number of frequency f, some midi numbers: E0(16), C1(24), C2(36), A4(69)

r(x), g(x), b(x)

red, green, and blue value of intensity x.

Default value is st(0, (midi(f)-59.5)/12); st(1, if(between(ld(0),0,1), 0.5-0.5*cos(2*PI*ld(0)), 0)); r(1-ld(1)) + b(ld(1)).

axisfile

Specify image file to draw the axis. This option override fontfile and fontcolor option.

axis, text

Enable/disable drawing text to the axis. If it is set to 0, drawing to the axis is disabled, ignoring fontfile and axisfile option. Default value is 1.

12.14.1 Examples

  • Playing audio while showing the spectrum:
    ffplay -f lavfi 'amovie=a.mp3, asplit [a][out1]; [a] showcqt [out0]'
    
  • Same as above, but with frame rate 30 fps:
    ffplay -f lavfi 'amovie=a.mp3, asplit [a][out1]; [a] showcqt=fps=30:count=5 [out0]'
    
  • Playing at 1280x720:
    ffplay -f lavfi 'amovie=a.mp3, asplit [a][out1]; [a] showcqt=s=1280x720:count=4 [out0]'
    
  • Disable sonogram display:
    sono_h=0
    
  • A1 and its harmonics: A1, A2, (near)E3, A3:
    ffplay -f lavfi 'aevalsrc=0.1*sin(2*PI*55*t)+0.1*sin(4*PI*55*t)+0.1*sin(6*PI*55*t)+0.1*sin(8*PI*55*t),
                     asplit[a][out1]; [a] showcqt [out0]'
    
  • Same as above, but with more accuracy in frequency domain:
    ffplay -f lavfi 'aevalsrc=0.1*sin(2*PI*55*t)+0.1*sin(4*PI*55*t)+0.1*sin(6*PI*55*t)+0.1*sin(8*PI*55*t),
                     asplit[a][out1]; [a] showcqt=timeclamp=0.5 [out0]'
    
  • Custom volume:
    bar_v=10:sono_v=bar_v*a_weighting(f)
    
  • Custom gamma, now spectrum is linear to the amplitude.
    bar_g=2:sono_g=2
    
  • Custom tlength equation:
    tc=0.33:tlength='st(0,0.17); 384*tc / (384 / ld(0) + tc*f /(1-ld(0))) + 384*tc / (tc*f / ld(0) + 384 /(1-ld(0)))'
    
  • Custom fontcolor and fontfile, C-note is colored green, others are colored blue:
    fontcolor='if(mod(floor(midi(f)+0.5),12), 0x0000FF, g(1))':fontfile=myfont.ttf
    
  • Custom frequency range with custom axis using image file:
    axisfile=myaxis.png:basefreq=40:endfreq=10000
    

12.15 showfreqs

Convert input audio to video output representing the audio power spectrum. Audio amplitude is on Y-axis while frequency is on X-axis.

The filter accepts the following options:

size, s

Specify size of video. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual. Default is 1024x512.

mode

Set display mode. This set how each frequency bin will be represented.

It accepts the following values:

line
bar
dot

Default is bar.

ascale

Set amplitude scale.

It accepts the following values:

lin

Linear scale.

sqrt

Square root scale.

cbrt

Cubic root scale.

log

Logarithmic scale.

Default is log.

fscale

Set frequency scale.

It accepts the following values:

lin

Linear scale.

log

Logarithmic scale.

rlog

Reverse logarithmic scale.

Default is lin.

win_size

Set window size.

It accepts the following values:

w16
w32
w64
w128
w256
w512
w1024
w2048
w4096
w8192
w16384
w32768
w65536

Default is w2048

win_func

Set windowing function.

It accepts the following values:

rect
bartlett
hanning
hamming
blackman
welch
flattop
bharris
bnuttall
bhann
sine
nuttall
lanczos
gauss
tukey

Default is hanning.

overlap

Set window overlap. In range [0, 1]. Default is 1, which means optimal overlap for selected window function will be picked.

averaging

Set time averaging. Setting this to 0 will display current maximal peaks. Default is 1, which means time averaging is disabled.

colors

Specify list of colors separated by space or by ’|’ which will be used to draw channel frequencies. Unrecognized or missing colors will be replaced by white color.

cmode

Set channel display mode.

It accepts the following values:

combined
separate

Default is combined.

12.16 showspectrum

Convert input audio to a video output, representing the audio frequency spectrum.

The filter accepts the following options:

size, s

Specify the video size for the output. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual. Default value is 640x512.

slide

Specify how the spectrum should slide along the window.

It accepts the following values:

replace

the samples start again on the left when they reach the right

scroll

the samples scroll from right to left

rscroll

the samples scroll from left to right

fullframe

frames are only produced when the samples reach the right

Default value is replace.

mode

Specify display mode.

It accepts the following values:

combined

all channels are displayed in the same row

separate

all channels are displayed in separate rows

Default value is ‘combined’.

color

Specify display color mode.

It accepts the following values:

channel

each channel is displayed in a separate color

intensity

each channel is displayed using the same color scheme

rainbow

each channel is displayed using the rainbow color scheme

moreland

each channel is displayed using the moreland color scheme

nebulae

each channel is displayed using the nebulae color scheme

fire

each channel is displayed using the fire color scheme

fiery

each channel is displayed using the fiery color scheme

fruit

each channel is displayed using the fruit color scheme

cool

each channel is displayed using the cool color scheme

Default value is ‘channel’.

scale

Specify scale used for calculating intensity color values.

It accepts the following values:

lin

linear

sqrt

square root, default

cbrt

cubic root

4thrt

4th root

5thrt

5th root

log

logarithmic

Default value is ‘sqrt’.

saturation

Set saturation modifier for displayed colors. Negative values provide alternative color scheme. 0 is no saturation at all. Saturation must be in [-10.0, 10.0] range. Default value is 1.

win_func

Set window function.

It accepts the following values:

rect
bartlett
hann
hanning
hamming
blackman
welch
flattop
bharris
bnuttall
bhann
sine
nuttall
lanczos
gauss
tukey

Default value is hann.

orientation

Set orientation of time vs frequency axis. Can be vertical or horizontal. Default is vertical.

overlap

Set ratio of overlap window. Default value is 0. When value is 1 overlap is set to recommended size for specific window function currently used.

gain

Set scale gain for calculating intensity color values. Default value is 1.

data

Set which data to display. Can be magnitude, default or phase.

The usage is very similar to the showwaves filter; see the examples in that section.

12.16.1 Examples

  • Large window with logarithmic color scaling:
    showspectrum=s=1280x480:scale=log
    
  • Complete example for a colored and sliding spectrum per channel using ffplay:
    ffplay -f lavfi 'amovie=input.mp3, asplit [a][out1];
                 [a] showspectrum=mode=separate:color=intensity:slide=1:scale=cbrt [out0]'
    

12.17 showspectrumpic

Convert input audio to a single video frame, representing the audio frequency spectrum.

The filter accepts the following options:

size, s

Specify the video size for the output. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual. Default value is 4096x2048.

mode

Specify display mode.

It accepts the following values:

combined

all channels are displayed in the same row

separate

all channels are displayed in separate rows

Default value is ‘combined’.

color

Specify display color mode.

It accepts the following values:

channel

each channel is displayed in a separate color

intensity

each channel is displayed using the same color scheme

rainbow

each channel is displayed using the rainbow color scheme

moreland

each channel is displayed using the moreland color scheme

nebulae

each channel is displayed using the nebulae color scheme

fire

each channel is displayed using the fire color scheme

fiery

each channel is displayed using the fiery color scheme

fruit

each channel is displayed using the fruit color scheme

cool

each channel is displayed using the cool color scheme

Default value is ‘intensity’.

scale

Specify scale used for calculating intensity color values.

It accepts the following values:

lin

linear

sqrt

square root, default

cbrt

cubic root

4thrt

4th root

5thrt

5th root

log

logarithmic

Default value is ‘log’.

saturation

Set saturation modifier for displayed colors. Negative values provide alternative color scheme. 0 is no saturation at all. Saturation must be in [-10.0, 10.0] range. Default value is 1.

win_func

Set window function.

It accepts the following values:

rect
bartlett
hann
hanning
hamming
blackman
welch
flattop
bharris
bnuttall
bhann
sine
nuttall
lanczos
gauss
tukey

Default value is hann.

orientation

Set orientation of time vs frequency axis. Can be vertical or horizontal. Default is vertical.

gain

Set scale gain for calculating intensity color values. Default value is 1.

legend

Draw time and frequency axes and legends. Default is enabled.

12.17.1 Examples

  • Extract an audio spectrogram of a whole audio track in a 1024x1024 picture using ffmpeg:
    ffmpeg -i audio.flac -lavfi showspectrumpic=s=1024x1024 spectrogram.png
    

12.18 showvolume

Convert input audio volume to a video output.

The filter accepts the following options:

rate, r

Set video rate.

b

Set border width, allowed range is [0, 5]. Default is 1.

w

Set channel width, allowed range is [80, 8192]. Default is 400.

h

Set channel height, allowed range is [1, 900]. Default is 20.

f

Set fade, allowed range is [0.001, 1]. Default is 0.95.

c

Set volume color expression.

The expression can use the following variables:

VOLUME

Current max volume of channel in dB.

CHANNEL

Current channel number, starting from 0.

t

If set, displays channel names. Default is enabled.

v

If set, displays volume values. Default is enabled.

o

Set orientation, can be horizontal or vertical, default is horizontal.

s

Set step size, allowed range s [0, 5]. Default is 0, which means step is disabled.

12.19 showwaves

Convert input audio to a video output, representing the samples waves.

The filter accepts the following options:

size, s

Specify the video size for the output. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual. Default value is 600x240.

mode

Set display mode.

Available values are:

point

Draw a point for each sample.

line

Draw a vertical line for each sample.

p2p

Draw a point for each sample and a line between them.

cline

Draw a centered vertical line for each sample.

Default value is point.

n

Set the number of samples which are printed on the same column. A larger value will decrease the frame rate. Must be a positive integer. This option can be set only if the value for rate is not explicitly specified.

rate, r

Set the (approximate) output frame rate. This is done by setting the option n. Default value is "25".

split_channels

Set if channels should be drawn separately or overlap. Default value is 0.

colors

Set colors separated by ’|’ which are going to be used for drawing of each channel.

scale

Set amplitude scale. Can be linear lin or logarithmic log. Default is linear.

12.19.1 Examples

  • Output the input file audio and the corresponding video representation at the same time:
    amovie=a.mp3,asplit[out0],showwaves[out1]
    
  • Create a synthetic signal and show it with showwaves, forcing a frame rate of 30 frames per second:
    aevalsrc=sin(1*2*PI*t)*sin(880*2*PI*t):cos(2*PI*200*t),asplit[out0],showwaves=r=30[out1]
    

12.20 showwavespic

Convert input audio to a single video frame, representing the samples waves.

The filter accepts the following options:

size, s

Specify the video size for the output. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual. Default value is 600x240.

split_channels

Set if channels should be drawn separately or overlap. Default value is 0.

colors

Set colors separated by ’|’ which are going to be used for drawing of each channel.

scale

Set amplitude scale. Can be linear lin or logarithmic log. Default is linear.

12.20.1 Examples

  • Extract a channel split representation of the wave form of a whole audio track in a 1024x800 picture using ffmpeg:
    ffmpeg -i audio.flac -lavfi showwavespic=split_channels=1:s=1024x800 waveform.png
    

12.21 spectrumsynth

Sythesize audio from 2 input video spectrums, first input stream represents magnitude across time and second represents phase across time. The filter will transform from frequency domain as displayed in videos back to time domain as presented in audio output.

This filter is primarly created for reversing processed showspectrum filter outputs, but can synthesize sound from other spectrograms too. But in such case results are going to be poor if the phase data is not available, because in such cases phase data need to be recreated, usually its just recreated from random noise. For best results use gray only output (channel color mode in showspectrum filter) and log scale for magnitude video and lin scale for phase video. To produce phase, for 2nd video, use data option. Inputs videos should generally use fullframe slide mode as that saves resources needed for decoding video.

The filter accepts the following options:

sample_rate

Specify sample rate of output audio, the sample rate of audio from which spectrum was generated may differ.

channels

Set number of channels represented in input video spectrums.

scale

Set scale which was used when generating magnitude input spectrum. Can be lin or log. Default is log.

slide

Set slide which was used when generating inputs spectrums. Can be replace, scroll, fullframe or rscroll. Default is fullframe.

win_func

Set window function used for resynthesis.

overlap

Set window overlap. In range [0, 1]. Default is 1, which means optimal overlap for selected window function will be picked.

orientation

Set orientation of input videos. Can be vertical or horizontal. Default is vertical.

12.21.1 Examples

  • First create magnitude and phase videos from audio, assuming audio is stereo with 44100 sample rate, then resynthesize videos back to audio with spectrumsynth:
    ffmpeg -i input.flac -lavfi showspectrum=mode=separate:scale=log:overlap=0.875:color=channel:slide=fullframe:data=magnitude -an -c:v rawvideo magnitude.nut
    ffmpeg -i input.flac -lavfi showspectrum=mode=separate:scale=lin:overlap=0.875:color=channel:slide=fullframe:data=phase -an -c:v rawvideo phase.nut
    ffmpeg -i magnitude.nut -i phase.nut -lavfi spectrumsynth=channels=2:sample_rate=44100:win_func=hann:overlap=0.875:slide=fullframe output.flac
    

12.22 split, asplit

Split input into several identical outputs.

asplit works with audio input, split with video.

The filter accepts a single parameter which specifies the number of outputs. If unspecified, it defaults to 2.

12.22.1 Examples

  • Create two separate outputs from the same input:
    [in] split [out0][out1]
    
  • To create 3 or more outputs, you need to specify the number of outputs, like in:
    [in] asplit=3 [out0][out1][out2]
    
  • Create two separate outputs from the same input, one cropped and one padded:
    [in] split [splitout1][splitout2];
    [splitout1] crop=100:100:0:0    [cropout];
    [splitout2] pad=200:200:100:100 [padout];
    
  • Create 5 copies of the input audio with ffmpeg:
    ffmpeg -i INPUT -filter_complex asplit=5 OUTPUT
    

12.23 zmq, azmq

Receive commands sent through a libzmq client, and forward them to filters in the filtergraph.

zmq and azmq work as a pass-through filters. zmq must be inserted between two video filters, azmq between two audio filters.

To enable these filters you need to install the libzmq library and headers and configure FFmpeg with --enable-libzmq.

For more information about libzmq see: http://www.zeromq.org/

The zmq and azmq filters work as a libzmq server, which receives messages sent through a network interface defined by the bind_address option.

The received message must be in the form:

TARGET COMMAND [ARG]

TARGET specifies the target of the command, usually the name of the filter class or a specific filter instance name.

COMMAND specifies the name of the command for the target filter.

ARG is optional and specifies the optional argument list for the given COMMAND.

Upon reception, the message is processed and the corresponding command is injected into the filtergraph. Depending on the result, the filter will send a reply to the client, adopting the format:

ERROR_CODE ERROR_REASON
MESSAGE

MESSAGE is optional.

12.23.1 Examples

Look at tools/zmqsend for an example of a zmq client which can be used to send commands processed by these filters.

Consider the following filtergraph generated by ffplay

ffplay -dumpgraph 1 -f lavfi "
color=s=100x100:c=red  [l];
color=s=100x100:c=blue [r];
nullsrc=s=200x100, zmq [bg];
[bg][l]   overlay      [bg+l];
[bg+l][r] overlay=x=100 "

To change the color of the left side of the video, the following command can be used:

echo Parsed_color_0 c yellow | tools/zmqsend

To change the right side:

echo Parsed_color_1 c pink | tools/zmqsend

13 Multimedia Sources

Below is a description of the currently available multimedia sources.

13.1 amovie

This is the same as movie source, except it selects an audio stream by default.

13.2 movie

Read audio and/or video stream(s) from a movie container.

It accepts the following parameters:

filename

The name of the resource to read (not necessarily a file; it can also be a device or a stream accessed through some protocol).

format_name, f

Specifies the format assumed for the movie to read, and can be either the name of a container or an input device. If not specified, the format is guessed from movie_name or by probing.

seek_point, sp

Specifies the seek point in seconds. The frames will be output starting from this seek point. The parameter is evaluated with av_strtod, so the numerical value may be suffixed by an IS postfix. The default value is "0".

streams, s

Specifies the streams to read. Several streams can be specified, separated by "+". The source will then have as many outputs, in the same order. The syntax is explained in the “Stream specifiers” section in the ffmpeg manual. Two special names, "dv" and "da" specify respectively the default (best suited) video and audio stream. Default is "dv", or "da" if the filter is called as "amovie".

stream_index, si

Specifies the index of the video stream to read. If the value is -1, the most suitable video stream will be automatically selected. The default value is "-1". Deprecated. If the filter is called "amovie", it will select audio instead of video.

loop

Specifies how many times to read the stream in sequence. If the value is less than 1, the stream will be read again and again. Default value is "1".

Note that when the movie is looped the source timestamps are not changed, so it will generate non monotonically increasing timestamps.

discontinuity

Specifies the time difference between frames above which the point is considered a timestamp discontinuity which is removed by adjusting the later timestamps.

It allows overlaying a second video on top of the main input of a filtergraph, as shown in this graph:

input -----------> deltapts0 --> overlay --> output
                                    ^
                                    |
movie --> scale--> deltapts1 -------+

13.2.1 Examples

  • Skip 3.2 seconds from the start of the AVI file in.avi, and overlay it on top of the input labelled "in":
    movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [over];
    [in] setpts=PTS-STARTPTS [main];
    [main][over] overlay=16:16 [out]
    
  • Read from a video4linux2 device, and overlay it on top of the input labelled "in":
    movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [over];
    [in] setpts=PTS-STARTPTS [main];
    [main][over] overlay=16:16 [out]
    
  • Read the first video stream and the audio stream with id 0x81 from dvd.vob; the video is connected to the pad named "video" and the audio is connected to the pad named "audio":
    movie=dvd.vob:s=v:0+#0x81 [video] [audio]
    

13.2.2 Commands

Both movie and amovie support the following commands:

seek

Perform seek using "av_seek_frame". The syntax is: seek stream_index|timestamp|flags

  • stream_index: If stream_index is -1, a default stream is selected, and timestamp is automatically converted from AV_TIME_BASE units to the stream specific time_base.
  • timestamp: Timestamp in AVStream.time_base units or, if no stream is specified, in AV_TIME_BASE units.
  • flags: Flags which select direction and seeking mode.
get_duration

Get movie duration in AV_TIME_BASE units.

14 See Also

ffmpeg, ffplay, ffprobe, ffserver, libavfilter

15 Authors

The FFmpeg developers.

For details about the authorship, see the Git history of the project (git://source.ffmpeg.org/ffmpeg), e.g. by typing the command git log in the FFmpeg source directory, or browsing the online repository at http://source.ffmpeg.org.

Maintainers for the specific components are listed in the file MAINTAINERS in the source code tree.

This document was generated on June 30, 2016 using makeinfo.