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 "filters.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_ON   1
	input is active More...
#define	INPUT_EOF   2
	input has reached EOF (may still be active) More...
#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. More...
static int	config_output (AVFilterLink *outlink)
static int	output_frame (AVFilterLink *outlink)
	Read samples from the input FIFOs, mix, and write to the output link. More...
static int	request_samples (AVFilterContext *ctx, int min_samples)
	Requests a frame, if needed, from each input link other than the first. More...
static int	calc_active_inputs (MixContext *s)
	Calculates the number of active inputs and determines EOF based on the duration option. More...
static int	activate (AVFilterContext *ctx)
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

INPUT_ON

#define INPUT_ON   1

input is active

Definition at line 48 of file af_amix.c.

Referenced by activate(), calc_active_inputs(), calculate_scales(), config_output(), output_frame(), and request_samples().

INPUT_EOF

#define INPUT_EOF   2

input has reached EOF (may still be active)

Definition at line 49 of file af_amix.c.

Referenced by activate(), output_frame(), and request_samples().

DURATION_LONGEST

#define DURATION_LONGEST   0

Definition at line 51 of file af_amix.c.

DURATION_SHORTEST

#define DURATION_SHORTEST   1

Definition at line 52 of file af_amix.c.

Referenced by calc_active_inputs().

DURATION_FIRST

#define DURATION_FIRST   2

Definition at line 53 of file af_amix.c.

Referenced by calc_active_inputs().

OFFSET

#define OFFSET

(

x

)

offsetof(MixContext, x)

Definition at line 180 of file af_amix.c.

A

#define A   AV_OPT_FLAG_AUDIO_PARAM

Definition at line 181 of file af_amix.c.

F

#define F   AV_OPT_FLAG_FILTERING_PARAM

Definition at line 182 of file af_amix.c.

Function Documentation

frame_list_clear()

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().

frame_list_next_frame_size()

static int frame_list_next_frame_size ( FrameList *  frame_list )

static

Definition at line 91 of file af_amix.c.

Referenced by activate(), and output_frame().

frame_list_next_pts()

static int64_t frame_list_next_pts ( FrameList *  frame_list )

static

Definition at line 98 of file af_amix.c.

Referenced by output_frame().

frame_list_remove_samples()

static void frame_list_remove_samples ( FrameList *  frame_list, int  nb_samples  )

static

Definition at line 105 of file af_amix.c.

Referenced by output_frame().

frame_list_add_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 activate().

AVFILTER_DEFINE_CLASS()

AVFILTER_DEFINE_CLASS

(

amix

)

calculate_scales()

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 208 of file af_amix.c.

Referenced by config_output(), and output_frame().

config_output()

static int config_output ( AVFilterLink *  outlink )

static

Definition at line 235 of file af_amix.c.

output_frame()

static int output_frame ( AVFilterLink *  outlink )

static

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

Definition at line 288 of file af_amix.c.

Referenced by activate(), and request_samples().

request_samples()

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 382 of file af_amix.c.

Referenced by activate().

calc_active_inputs()

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 406 of file af_amix.c.

Referenced by activate().

activate()

static int activate ( AVFilterContext *  ctx )

static

Definition at line 421 of file af_amix.c.

Referenced by compressor(), config_output(), filter_frame(), and gate().

init()

static av_cold int init ( AVFilterContext *  ctx )

static

Definition at line 504 of file af_amix.c.

uninit()

static av_cold void uninit ( AVFilterContext *  ctx )

static

Definition at line 552 of file af_amix.c.

query_formats()

static int query_formats ( AVFilterContext *  ctx )

static

Definition at line 574 of file af_amix.c.

Variable Documentation

amix_options

const AVOption amix_options[]

static

Initial value:

= {
    { "inputs", "Number of inputs.",
            OFFSET(nb_inputs), AV_OPT_TYPE_INT, { .i64 = 2 }, 1, 1024, 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  }, 0, 0, A|F, "duration" },
        { "shortest", "Duration of shortest input.", 0, AV_OPT_TYPE_CONST, { .i64 = DURATION_SHORTEST }, 0, 0, A|F, "duration" },
        { "first",    "Duration of first input.",    0, AV_OPT_TYPE_CONST, { .i64 = DURATION_FIRST    }, 0, 0, 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 },
    { "weights", "Set weight for each input.",
            OFFSET(weights_str), AV_OPT_TYPE_STRING, {.str="1 1"}, 0, 0, A|F },
    { NULL }
}

Definition at line 183 of file af_amix.c.

avfilter_af_amix_outputs

const AVFilterPad avfilter_af_amix_outputs[]

static

Initial value:

= {
    {
        .name          = "default",
        .type          = AVMEDIA_TYPE_AUDIO,
        .config_props  = config_output,
    },
    { NULL }
}

Definition at line 602 of file af_amix.c.

ff_af_amix

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,
    .uninit         = uninit,
    .activate       = activate,
    .query_formats  = query_formats,
    .inputs         = NULL,
    .outputs        = avfilter_af_amix_outputs,
    .flags          = AVFILTER_FLAG_DYNAMIC_INPUTS,
}

Definition at line 611 of file af_amix.c.