FFmpeg
Functions | Variables
alsa_dec.c File Reference
#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
 
const 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 141 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 146 of file alsa_dec.c.

◆ alsa_demuxer_class

const AVClass alsa_demuxer_class
static
Initial value:
= {
.class_name = "ALSA indev",
.item_name = av_default_item_name,
.option = options,
}

Definition at line 152 of file alsa_dec.c.

◆ ff_alsa_demuxer

const AVInputFormat ff_alsa_demuxer
Initial value:
= {
.name = "alsa",
.long_name = NULL_IF_CONFIG_SMALL("ALSA audio input"),
.priv_data_size = sizeof(AlsaData),
.get_device_list = audio_get_device_list,
.priv_class = &alsa_demuxer_class,
}

Definition at line 160 of file alsa_dec.c.

read_close
static av_cold int read_close(AVFormatContext *ctx)
Definition: libcdio.c:142
AV_CLASS_CATEGORY_DEVICE_AUDIO_INPUT
@ AV_CLASS_CATEGORY_DEVICE_AUDIO_INPUT
Definition: log.h:44
LIBAVUTIL_VERSION_INT
#define LIBAVUTIL_VERSION_INT
Definition: version.h:85
read_header
static int read_header(FFV1Context *f)
Definition: ffv1dec.c:527
NULL
#define NULL
Definition: coverity.c:32
alsa_demuxer_class
static const AVClass alsa_demuxer_class
Definition: alsa_dec.c:152
AlsaData
Definition: alsa.h:48
audio_read_header
static av_cold int audio_read_header(AVFormatContext *s1)
Definition: alsa_dec.c:60
av_default_item_name
const char * av_default_item_name(void *ptr)
Return the context name.
Definition: log.c:235
ff_alsa_close
av_cold int ff_alsa_close(AVFormatContext *s1)
Close the ALSA PCM.
Definition: alsa.c:303
NULL_IF_CONFIG_SMALL
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification.
Definition: internal.h:117
AVFMT_NOFILE
#define AVFMT_NOFILE
Demuxer will use avio_open, no opened file should be provided by the caller.
Definition: avformat.h:463
AV_OPT_FLAG_DECODING_PARAM
#define AV_OPT_FLAG_DECODING_PARAM
a generic parameter which can be set by the user for demuxing or decoding
Definition: opt.h:279
read_packet
static int read_packet(void *opaque, uint8_t *buf, int buf_size)
Definition: avio_reading.c:42
AV_OPT_TYPE_INT
@ AV_OPT_TYPE_INT
Definition: opt.h:225
audio_get_device_list
static int audio_get_device_list(AVFormatContext *h, AVDeviceInfoList *device_list)
Definition: alsa_dec.c:141
options
static const AVOption options[]
Definition: alsa_dec.c:146
flags
#define flags(name, subs,...)
Definition: cbs_av1.c:561
audio_read_packet
static int audio_read_packet(AVFormatContext *s1, AVPacket *pkt)
Definition: alsa_dec.c:101