alsa.c File Reference

ALSA input and output: common code. More...

#include <alsa/asoundlib.h>
#include "avdevice.h"
#include "libavutil/avassert.h"
#include "libavutil/channel_layout.h"
#include "alsa.h"

Macros
#define	MAKE_REORDER_FUNC(NAME, TYPE, CHANNELS, LAYOUT, MAP)
#define	MAKE_REORDER_FUNCS(CHANNELS, LAYOUT, MAP)
#define	FORMAT_I8   0
#define	FORMAT_I16   1
#define	FORMAT_I32   2
#define	FORMAT_F32   3
#define	PICK_REORDER(layout)

Functions
	MAKE_REORDER_FUNCS (5, out_50, out [0]=in[0];out[1]=in[1];out[2]=in[3];out[3]=in[4];out[4]=in[2];)
av_cold int	ff_alsa_open (AVFormatContext *ctx, snd_pcm_stream_t mode, unsigned int *sample_rate, int channels, enum AVCodecID *codec_id)
	Open an ALSA PCM. More...
av_cold int	ff_alsa_close (AVFormatContext *s1)
	Close the ALSA PCM. More...
int	ff_alsa_xrun_recover (AVFormatContext *s1, int err)
	Try to recover from ALSA buffer underrun. More...
int	ff_alsa_extend_reorder_buf (AlsaData *s, int min_size)
int	ff_alsa_get_device_list (AVDeviceInfoList *device_list, snd_pcm_stream_t stream_type)

Detailed Description

ALSA input and output: common code.

Author

Luca Abeni ( lucabe72 email it )

Benoit Fouet ( benoit fouet free fr )

Nicolas George ( nicolas george normalesup org )

Macro Definition Documentation

MAKE_REORDER_FUNC

#define MAKE_REORDER_FUNC	(		NAME,
			TYPE,
			CHANNELS,
			LAYOUT,
			MAP
	)

Value:

static void alsa_reorder_ ## NAME ## _ ## LAYOUT(const void *in_v,          \
                                                 void *out_v,               \
                                                 int n)                     \
{                                                                           \
    const TYPE *in = in_v;                                                  \
    TYPE      *out = out_v;                                                 \
                                                                            \
    while (n-- > 0) {                                                       \
        MAP                                                                 \
        in  += CHANNELS;                                                    \
        out += CHANNELS;                                                    \
    }                                                                       \
}

MAKE_REORDER_FUNCS

#define MAKE_REORDER_FUNCS	(		CHANNELS,
			LAYOUT,
			MAP
	)

Value:

MAKE_REORDER_FUNC(int8,  int8_t,  CHANNELS, LAYOUT, MAP) \
    MAKE_REORDER_FUNC(int16, int16_t, CHANNELS, LAYOUT, MAP) \
    MAKE_REORDER_FUNC(int32, int32_t, CHANNELS, LAYOUT, MAP) \
    MAKE_REORDER_FUNC(f32,   float,   CHANNELS, LAYOUT, MAP)

PICK_REORDER

#define PICK_REORDER

(

layout

)

Value:

switch(format) {\
    case FORMAT_I8:  s->reorder_func = alsa_reorder_int8_out_ ##layout;  break;\
    case FORMAT_I16: s->reorder_func = alsa_reorder_int16_out_ ##layout; break;\
    case FORMAT_I32: s->reorder_func = alsa_reorder_int32_out_ ##layout; break;\
    case FORMAT_F32: s->reorder_func = alsa_reorder_f32_out_ ##layout;   break;\
}

Function Documentation

ff_alsa_close()

av_cold int ff_alsa_close

(

AVFormatContext *

s1

)

Close the ALSA PCM.

Parameters

s1	media file handle

Returns

0

ff_alsa_open()

av_cold int ff_alsa_open	(	AVFormatContext *	s,
		snd_pcm_stream_t	mode,
		unsigned int *	sample_rate,
		int	channels,
		enum AVCodecID *	codec_id
	)

Open an ALSA PCM.

Parameters

s	media file handle
mode	either SND_PCM_STREAM_CAPTURE or SND_PCM_STREAM_PLAYBACK
sample_rate	in: requested sample rate; out: actually selected sample rate
channels	number of channels
codec_id	in: requested AVCodecID or AV_CODEC_ID_NONE; out: actually selected AVCodecID, changed only if AV_CODEC_ID_NONE was requested

Returns

0 if OK, AVERROR_xxx on error

ff_alsa_xrun_recover()

int ff_alsa_xrun_recover	(	AVFormatContext *	s1,
		int	err
	)

Try to recover from ALSA buffer underrun.

Parameters

s1	media file handle
err	error code reported by the previous ALSA call

Returns

0 if OK, AVERROR_xxx on error