libavdevice/alsa-audio-dec.c File Reference

ALSA input and output: input. More...

#include <alsa/asoundlib.h>
#include "libavformat/internal.h"
#include "libavutil/opt.h"
#include "libavutil/mathematics.h"
#include "avdevice.h"
#include "alsa-audio.h"

Go to the source code of this file.

Functions
static av_cold int	audio_read_header (AVFormatContext *s1, AVFormatParameters *ap)
static int	audio_read_packet (AVFormatContext *s1, AVPacket *pkt)
Variables
static const AVOption	options []
static const AVClass	alsa_demuxer_class
AVInputFormat	ff_alsa_demuxer

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Detailed Description

ALSA input and output: input.

Author:

Luca Abeni ( lucabe72 email it )

Benoit Fouet ( benoit fouet free fr )

Nicolas George ( nicolas george normalesup org )

This avdevice decoder allows to capture audio from an ALSA (Advanced Linux Sound Architecture) device.

The filename parameter is the name of an ALSA PCM device capable of capture, for example "default" or "plughw:1"; see the ALSA documentation for naming conventions. The empty string is equivalent to "default".

The capture period is set to the lower value available for the device, which gives a low latency suitable for real-time capture.

The PTS are an Unix time in microsecond.

Due to a bug in the ALSA library (https://bugtrack.alsa-project.org/alsa-bug/view.php?id=4308), this decoder does not work with certain ALSA plugins, especially the dsnoop plugin.

Definition in file alsa-audio-dec.c.

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Function Documentation

static av_cold int audio_read_header	(	AVFormatContext *	s1,
		AVFormatParameters *	ap
	)			[static]

Definition at line 56 of file alsa-audio-dec.c.

static int audio_read_packet	(	AVFormatContext *	s1,
		AVPacket *	pkt
	)			[static]

Definition at line 98 of file alsa-audio-dec.c.

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Variable Documentation

const AVClass alsa_demuxer_class [static]

Initial value:

 {
    .class_name     = "ALSA demuxer",
    .item_name      = av_default_item_name,
    .option         = options,
    .version        = LIBAVUTIL_VERSION_INT,
}

Definition at line 141 of file alsa-audio-dec.c.

AVInputFormat ff_alsa_demuxer

Initial value:

 {
    .name           = "alsa",
    .long_name      = NULL_IF_CONFIG_SMALL("ALSA audio input"),
    .priv_data_size = sizeof(AlsaData),
    .read_header    = audio_read_header,
    .read_packet    = audio_read_packet,
    .read_close     = ff_alsa_close,
    .flags          = AVFMT_NOFILE,
    .priv_class     = &alsa_demuxer_class,
}

Definition at line 148 of file alsa-audio-dec.c.

const AVOption options[] [static]

Initial value:

 {
    { "sample_rate", "", 0x42, AV_OPT_TYPE_INT, {.dbl = 48000}, 1, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
    { "channels",    "", 0x42,    AV_OPT_TYPE_INT, {.dbl = 2},     1, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
    { NULL },
}

Definition at line 135 of file alsa-audio-dec.c.