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af_amix.c File Reference

Audio Mix Filter. More...

#include "libavutil/attributes.h"
#include "libavutil/audio_fifo.h"
#include "libavutil/avassert.h"
#include "libavutil/avstring.h"
#include "libavutil/channel_layout.h"
#include "libavutil/common.h"
#include "libavutil/float_dsp.h"
#include "libavutil/mathematics.h"
#include "libavutil/opt.h"
#include "libavutil/samplefmt.h"
#include "audio.h"
#include "avfilter.h"
#include "formats.h"
#include "internal.h"

Go to the source code of this file.

Data Structures

struct  FrameInfo
 
struct  FrameList
 Linked list used to store timestamps and frame sizes of all frames in the FIFO for the first input. More...
 
struct  MixContext
 

Macros

#define INPUT_OFF   0
 input has reached EOF
 
#define INPUT_ON   1
 input is active
 
#define INPUT_INACTIVE   2
 input is on, but is currently inactive
 
#define DURATION_LONGEST   0
 
#define DURATION_SHORTEST   1
 
#define DURATION_FIRST   2
 
#define OFFSET(x)   offsetof(MixContext, x)
 
#define A   AV_OPT_FLAG_AUDIO_PARAM
 
#define F   AV_OPT_FLAG_FILTERING_PARAM
 

Functions

static void frame_list_clear (FrameList *frame_list)
 
static int frame_list_next_frame_size (FrameList *frame_list)
 
static int64_t frame_list_next_pts (FrameList *frame_list)
 
static void frame_list_remove_samples (FrameList *frame_list, int nb_samples)
 
static int frame_list_add_frame (FrameList *frame_list, int nb_samples, int64_t pts)
 
 AVFILTER_DEFINE_CLASS (amix)
 
static void calculate_scales (MixContext *s, int nb_samples)
 Update the scaling factors to apply to each input during mixing.
 
static int config_output (AVFilterLink *outlink)
 
static int output_frame (AVFilterLink *outlink, int nb_samples)
 Read samples from the input FIFOs, mix, and write to the output link.
 
static int get_available_samples (MixContext *s)
 Returns the smallest number of samples available in the input FIFOs other than that of the first input.
 
static int request_samples (AVFilterContext *ctx, int min_samples)
 Requests a frame, if needed, from each input link other than the first.
 
static int calc_active_inputs (MixContext *s)
 Calculates the number of active inputs and determines EOF based on the duration option.
 
static int request_frame (AVFilterLink *outlink)
 
static int filter_frame (AVFilterLink *inlink, AVFrame *buf)
 
static av_cold int init (AVFilterContext *ctx)
 
static av_cold void uninit (AVFilterContext *ctx)
 
static int query_formats (AVFilterContext *ctx)
 

Variables

static const AVOption amix_options []
 
static const AVFilterPad avfilter_af_amix_outputs []
 
AVFilter ff_af_amix
 

Detailed Description

Audio Mix Filter.

Mixes audio from multiple sources into a single output. The channel layout, sample rate, and sample format will be the same for all inputs and the output.

Definition in file af_amix.c.

Macro Definition Documentation

#define INPUT_OFF   0

input has reached EOF

Definition at line 47 of file af_amix.c.

Referenced by calc_active_inputs(), get_available_samples(), request_frame(), and request_samples().

#define INPUT_ON   1

input is active

Definition at line 48 of file af_amix.c.

Referenced by calculate_scales(), config_output(), and output_frame().

#define INPUT_INACTIVE   2

input is on, but is currently inactive

Definition at line 49 of file af_amix.c.

#define DURATION_LONGEST   0

Definition at line 51 of file af_amix.c.

#define DURATION_SHORTEST   1

Definition at line 52 of file af_amix.c.

Referenced by calc_active_inputs().

#define DURATION_FIRST   2

Definition at line 53 of file af_amix.c.

Referenced by calc_active_inputs().

#define OFFSET (   x)    offsetof(MixContext, x)

Definition at line 176 of file af_amix.c.

#define A   AV_OPT_FLAG_AUDIO_PARAM

Definition at line 177 of file af_amix.c.

Definition at line 178 of file af_amix.c.

Function Documentation

static void frame_list_clear ( FrameList frame_list)
static

Definition at line 77 of file af_amix.c.

Referenced by frame_list_remove_samples(), and uninit().

static int frame_list_next_frame_size ( FrameList frame_list)
static

Definition at line 91 of file af_amix.c.

Referenced by request_frame().

static int64_t frame_list_next_pts ( FrameList frame_list)
static

Definition at line 98 of file af_amix.c.

Referenced by request_frame().

static void frame_list_remove_samples ( FrameList frame_list,
int  nb_samples 
)
static

Definition at line 105 of file af_amix.c.

Referenced by request_frame().

static int frame_list_add_frame ( FrameList frame_list,
int  nb_samples,
int64_t  pts 
)
static

Definition at line 132 of file af_amix.c.

Referenced by filter_frame().

AVFILTER_DEFINE_CLASS ( amix  )
static void calculate_scales ( MixContext s,
int  nb_samples 
)
static

Update the scaling factors to apply to each input during mixing.

This balances the full volume range between active inputs and handles volume transitions when EOF is encountered on an input but mixing continues with the remaining inputs.

Definition at line 202 of file af_amix.c.

Referenced by config_output(), and output_frame().

static int config_output ( AVFilterLink outlink)
static

Definition at line 219 of file af_amix.c.

static int output_frame ( AVFilterLink outlink,
int  nb_samples 
)
static

Read samples from the input FIFOs, mix, and write to the output link.

Definition at line 270 of file af_amix.c.

Referenced by request_frame().

static int get_available_samples ( MixContext s)
static

Returns the smallest number of samples available in the input FIFOs other than that of the first input.

Definition at line 320 of file af_amix.c.

Referenced by request_frame().

static int request_samples ( AVFilterContext ctx,
int  min_samples 
)
static

Requests a frame, if needed, from each input link other than the first.

Definition at line 342 of file af_amix.c.

Referenced by request_frame().

static int calc_active_inputs ( MixContext s)
static

Calculates the number of active inputs and determines EOF based on the duration option.

Returns
0 if mixing should continue, or AVERROR_EOF if mixing should stop.

Definition at line 372 of file af_amix.c.

Referenced by request_frame().

static int request_frame ( AVFilterLink outlink)
static

Definition at line 387 of file af_amix.c.

static int filter_frame ( AVFilterLink inlink,
AVFrame buf 
)
static

Definition at line 454 of file af_amix.c.

Referenced by init().

static av_cold int init ( AVFilterContext ctx)
static

Definition at line 487 of file af_amix.c.

static av_cold void uninit ( AVFilterContext ctx)
static

Definition at line 509 of file af_amix.c.

static int query_formats ( AVFilterContext ctx)
static

Definition at line 528 of file af_amix.c.

Variable Documentation

const AVOption amix_options[]
static
Initial value:
= {
{ "inputs", "Number of inputs.",
OFFSET(nb_inputs), AV_OPT_TYPE_INT, { .i64 = 2 }, 1, 32, A|F },
{ "duration", "How to determine the end-of-stream.",
OFFSET(duration_mode), AV_OPT_TYPE_INT, { .i64 = DURATION_LONGEST }, 0, 2, A|F, "duration" },
{ "longest", "Duration of longest input.", 0, AV_OPT_TYPE_CONST, { .i64 = DURATION_LONGEST }, INT_MIN, INT_MAX, A|F, "duration" },
{ "shortest", "Duration of shortest input.", 0, AV_OPT_TYPE_CONST, { .i64 = DURATION_SHORTEST }, INT_MIN, INT_MAX, A|F, "duration" },
{ "first", "Duration of first input.", 0, AV_OPT_TYPE_CONST, { .i64 = DURATION_FIRST }, INT_MIN, INT_MAX, A|F, "duration" },
{ "dropout_transition", "Transition time, in seconds, for volume "
"renormalization when an input stream ends.",
OFFSET(dropout_transition), AV_OPT_TYPE_FLOAT, { .dbl = 2.0 }, 0, INT_MAX, A|F },
{ NULL }
}

Definition at line 179 of file af_amix.c.

const AVFilterPad avfilter_af_amix_outputs[]
static
Initial value:
= {
{
.name = "default",
.config_props = config_output,
.request_frame = request_frame
},
{ NULL }
}

Definition at line 546 of file af_amix.c.

AVFilter ff_af_amix
Initial value:
= {
.name = "amix",
.description = NULL_IF_CONFIG_SMALL("Audio mixing."),
.priv_size = sizeof(MixContext),
.priv_class = &amix_class,
.init = init,
.inputs = NULL,
}

Definition at line 556 of file af_amix.c.