FFmpeg Filtering Guide

FFmpeg has access to many filters and more are added on a regular basis. To see what filters are available with your build see ffmpeg -filters. Refer to the libavfilter documentation for more information and examples. This wiki page is for user contributed examples and tips. Contributions to this page are encouraged.

Examples

Scaling

Starting with something simple. Resize a 640x480 input to a 320x240 output.

ffmpeg -i input -vf scale=iw/2:-1 output

iw is input width. In this example the input width is 640. 640/2 = 320. The -1 tells the scale filter to preserve the aspect ratio of the output, so in this example the scale filter will choose a value of 240. See the libavfilter documentation for additional information.

Speed up your video

Increase the speed of a 20 minute video to fit 1 minute output. 1 minute / 20 minutes = 0.05.

ffmpeg -i input -vf setpts=0.05*PTS output

Note that this method will drop frames to achieve your desired speed.

Filtergraph,Chain,Filter relationship

What follows the -vf in an ffmpeg command line is a Filtergraph description. This filtergraph may contain a number of chains, each of which may contain a number of filters.

Whilst a full filtergraph description can be complicated, it is possible to simplify it for simpler graphs provided ambiguity is avoided.

Remembering that filters in a chain are separated by commas "," chains by a semicolon ";" and that if an input or output is not specified it is assumed to come from the preceding or sent to the following item in the chain.

The following are equivalent:-

ffmpeg -i input -vf [in]scale=iw/2:-1[out] output
ffmpeg -i input -vf scale=iw/2:-1 output                                      # the input and output are implied without ambiguity

As are:-

ffmpeg -i input -vf [in]yadif=0:0:0[middle];[middle]scale=iw/2:-1[out] output # 2 chains form, one filter per chain, chains linked by the [middle] pad
ffmpeg -i input -vf [in]yadif=0:0:0,scale=iw/2:-1[out] output                 # 1 chain form, with 2 filters in the chain, linking implied
ffmpeg -i input -vf yadif=0:0:0,scale=iw/2:-1  output                         # the input and output are implied without ambiguity

Escaping characters

As described in the documentation, it can be necessary to escape commas "," that need to appear in some arguments, for example the select filter:-

ffmpeg -i input -vf select='eq(pict_type\,I)' output                         #to select only I frames

However an alternative, which also allows for white space within the filtergraph, and which may assist in clarity of reading complex graphs, is to enclose the whole filtergraph within double quotes " " thus:-

ffmpeg -i input -vf "select=eq(pict_type,I)" output                          #to select only I frames
ffmpeg -i input -vf "yadif=0:-1:0, scale=iw/2:-1" output                     # deinterlace then resize

Note that the examples given in the documentation mix and match the use of "full quoting" and "\" escaping, and that use of unusual shells may upset escaping.

Burnt in Timecode

PAL 25fps non drop frame

ffmpeg -i in.mp4 -vf "drawtext=fontfile=/usr/share/fonts/truetype/DroidSans.ttf: timecode='09\:57\:00\:00': r=25: \
x=(w-tw)/2: y=h-(2*lh): fontcolor=white: box=1: boxcolor=0x00000000@1" -an -y out.mp4

NTSC 30fps drop frame

(change the : to a ; before the frame count)_________________________________________________________
                                                                                                     \
ffmpeg -i in.mp4 -vf "drawtext=fontfile=/usr/share/fonts/truetype/DroidSans.ttf: timecode='09\:57\:00\;00': r=30: \
x=(w-tw)/2: y=h-(2*lh): fontcolor=white: box=1: boxcolor=0x00000000@1" -an -y out.mp4

Scripting your command line parameters

If building complex filtergraphs the command line can get very messy so it can help to break things down into manageable pieces. However one needs to be careful when joining them all together to avoid issues due to your shell and escaped characters.

The following example shows a sample bash script containing a filtergraph of one chain with three filters; yadif, scale and drawtext.

#!/bin/bash
# ffmpeg test script

path="/path/to/file/"

in_file="in.mp4"
out_file="out.mp4"

cd $path

filter="-vf \"yadif=0:-1:0, scale=400:226, drawtext=fontfile=/usr/share/fonts/truetype/DroidSans.ttf: \
text='tod- %X':x=(w-text_w)/2:y=H-60 :fontcolor=white :box=1:boxcolor=0x00000000@1\""
codec="-vcodec libx264  -pix_fmt yuv420p -b:v 700k -r 25 -maxrate 700k -bufsize 5097k"

command_line="ffmpeg -i $in_file $filter $codec -an $out_file"

echo $command_line
eval $command_line
exit

Note that the double quotes " around the whole filtergraph have been escaped \" and the filtergraph spans more than one line, the echo command shows the full command as it is executed. Useful for debugging.

The eval invocation of the $command_line variable is required to avoid loss of the embedded escaped quotes which occurs if it is absent. Other shells may behave differently.

List of Filters

Filters bundled with libavfilter as of 2.50.0:

Filters:
aconvert         Convert the input audio to sample_fmt:channel_layout:packed_fmt.
aformat          Convert the input audio to one of the specified formats.
anull            Pass the source unchanged to the output.
aresample        Resample audio data.
ashowinfo        Show textual information for each audio frame.
earwax           Widen the stereo image.
pan              Remix channels with coefficients (panning)
volume           Change input volume.
abuffer          Buffer audio frames, and make them accessible to the filterchain.
aevalsrc         Generate an audio signal generated by an expression.
amovie           Read audio from a movie source.
anullsrc         Null audio source, return empty audio frames.
abuffersink      Buffer audio frames, and make them available to the end of the filter graph.
anullsink        Do absolutely nothing with the input audio.
blackframe       Detect frames that are (almost) black.
boxblur          Blur the input.
copy             Copy the input video unchanged to the output.
crop             Crop the input video to width:height:x:y.
cropdetect       Auto-detect crop size.
delogo           Remove logo from input video.
deshake          Stabilize shaky video.
drawbox          Draw a colored box on the input video.
fade             Fade in/out input video
fieldorder       Set the field order.
fifo             Buffer input images and send them when they are requested.
format           Convert the input video to one of the specified pixel formats.
gradfun          Debands video quickly using gradients.
hflip            Horizontally flip the input video.
hqdn3d           Apply a High Quality 3D Denoiser.
lut              Compute and apply a lookup table to the RGB/YUV input video.
lutrgb           Compute and apply a lookup table to the RGB input video.
lutyuv           Compute and apply a lookup table to the YUV input video.
mp               libmpcodecs wrapper.
negate           Negate input video.
noformat         Force libavfilter not to use any of the specified pixel formats for the input to the next filter.
null             Pass the source unchanged to the output.
overlay          Overlay a video source on top of the input.
pad              Pad input image to width:height[:x:y[:color]] (default x and y: 0, default color: black).
pixdesctest      Test pixel format definitions.
scale            Scale the input video to width:height size and/or convert the image format.
select           Select frames to pass in output.
setdar           Set the frame display aspect ratio.
setpts           Set PTS for the output video frame.
setsar           Set the pixel sample aspect ratio.
settb            Set timebase for the output link.
showinfo         Show textual information for each video frame.
slicify          Pass the images of input video on to next video filter as multiple slices.
split            Pass on the input to two outputs.
transpose        Transpose input video.
unsharp          Sharpen or blur the input video.
vflip            Flip the input video vertically.
yadif            Deinterlace the input image
buffer           Buffer video frames, and make them accessible to the filterchain.
color            Provide an uniformly colored input, syntax is: [color[:size[:rate]]]
mandelbrot       Mandelbrot fractal renderer
movie            Read from a movie source.
mptestsrc        Generate various test pattern.
nullsrc          Null video source, return unprocessed video frames.
rgbtestsrc       Generate RGB test pattern.
testsrc          Generate test pattern.
buffersink       Buffer video frames, and make them available to the end of the filter graph.
nullsink         Do absolutely nothing with the input video.

Other Filters

Other filters created by users:

•  https://github.com/indiefan/FFmpeg-Filters an updated vf_fade filter.