alsa_dec.c File Reference

ALSA input and output: input. More...

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

Go to the source code of this file.

Functions
static av_cold int	audio_read_header (AVFormatContext *s1)
static int	audio_read_packet (AVFormatContext *s1, AVPacket *pkt)
static int	audio_get_device_list (AVFormatContext *h, AVDeviceInfoList *device_list)

Variables
static const AVOption	options []
static const AVClass	alsa_demuxer_class
AVInputFormat	ff_alsa_demuxer

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 can 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_dec.c.

Function Documentation

audio_read_header()

static av_cold int audio_read_header ( AVFormatContext *  s1 )

static

Definition at line 60 of file alsa_dec.c.

audio_read_packet()

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

static

Definition at line 101 of file alsa_dec.c.

audio_get_device_list()

static int audio_get_device_list ( AVFormatContext *  h, AVDeviceInfoList *  device_list  )

static

Definition at line 139 of file alsa_dec.c.

Variable Documentation

options

const AVOption options[]

static

Initial value:

= {
    { "sample_rate", "", 0x42, AV_OPT_TYPE_INT, {.i64 = 48000}, 1, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
    { "channels",    "", 0x42,    AV_OPT_TYPE_INT, {.i64 = 2},     1, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
    { NULL },
}

Definition at line 144 of file alsa_dec.c.

alsa_demuxer_class

const AVClass alsa_demuxer_class

static

Initial value:

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

Definition at line 150 of file alsa_dec.c.

ff_alsa_demuxer

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,
    .get_device_list = audio_get_device_list,
    .flags          = AVFMT_NOFILE,
    .priv_class     = &alsa_demuxer_class,
}

Definition at line 158 of file alsa_dec.c.