Simple DirectMedia Layer

Copyright (C) 1997-2011 Sam Lantinga <slouken@libsdl.org>

This software is provided 'as-is', without any express or implied

warranty. In no event will the authors be held liable for any damages

arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,

including commercial applications, and to alter it and redistribute it

freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not

claim that you wrote the original software. If you use this software

in a product, an acknowledgment in the product documentation would be

appreciated but is not required.

2. Altered source versions must be plainly marked as such, and must not be

misrepresented as being the original software.

3. This notice may not be removed or altered from any source distribution.

/* Allow access to a raw mixing buffer */

#include <sys/types.h>

#include <errno.h>

#include <string.h>

#include "SDL_timer.h"

#include "SDL_audio.h"

#include "../SDL_audiomem.h"

#include "../SDL_audio_c.h"

#include "SDL_alsa_audio.h"

#ifdef SDL_AUDIO_DRIVER_ALSA_DYNAMIC

#include "SDL_loadso.h"

#endif

/* The tag name used by ALSA audio */

#define DRIVER_NAME "alsa"

(snd_pcm_t **, const char *, snd_pcm_stream_t, int);

static int (*ALSA_snd_pcm_close) (snd_pcm_t * pcm);

static int (*ALSA_snd_pcm_prepare) (snd_pcm_t *);

static int (*ALSA_snd_pcm_drain) (snd_pcm_t *);

static const char *(*ALSA_snd_strerror) (int);

static size_t(*ALSA_snd_pcm_hw_params_sizeof) (void);

static size_t(*ALSA_snd_pcm_sw_params_sizeof) (void);

static void (*ALSA_snd_pcm_hw_params_copy)

(snd_pcm_hw_params_t *, const snd_pcm_hw_params_t *);

static int (*ALSA_snd_pcm_hw_params_get_channels)

(const snd_pcm_hw_params_t *, unsigned int *);

static int (*ALSA_snd_pcm_hw_params_set_rate_near)

(snd_pcm_t *, snd_pcm_hw_params_t *, unsigned int *, int *);

static int (*ALSA_snd_pcm_hw_params_set_period_size_near)

(snd_pcm_t *, snd_pcm_hw_params_t *, snd_pcm_uframes_t *, int *);

static int (*ALSA_snd_pcm_hw_params_get_period_size)

(const snd_pcm_hw_params_t *, snd_pcm_uframes_t *, int *);

static int (*ALSA_snd_pcm_hw_params_set_periods_near)

(snd_pcm_t *, snd_pcm_hw_params_t *, unsigned int *, int *);

static int (*ALSA_snd_pcm_hw_params_get_periods)

(const snd_pcm_hw_params_t *, unsigned int *, int *);

static int (*ALSA_snd_pcm_hw_params_set_buffer_size_near)

(snd_pcm_t *pcm, snd_pcm_hw_params_t *, snd_pcm_uframes_t *);

static int (*ALSA_snd_pcm_hw_params_get_buffer_size)

(const snd_pcm_hw_params_t *, snd_pcm_uframes_t *);

static int (*ALSA_snd_pcm_hw_params) (snd_pcm_t *, snd_pcm_hw_params_t *);

static int (*ALSA_snd_pcm_sw_params_current) (snd_pcm_t *,

snd_pcm_sw_params_t *);

(snd_pcm_t *, snd_pcm_sw_params_t *, snd_pcm_uframes_t);

static int (*ALSA_snd_pcm_sw_params) (snd_pcm_t *, snd_pcm_sw_params_t *);

static int (*ALSA_snd_pcm_nonblock) (snd_pcm_t *, int);

#define snd_pcm_hw_params_sizeof ALSA_snd_pcm_hw_params_sizeof

#define snd_pcm_sw_params_sizeof ALSA_snd_pcm_sw_params_sizeof

static void *alsa_handle = NULL;

static int

load_alsa_sym(const char *fn, void **addr)

*addr = SDL_LoadFunction(alsa_handle, fn);

if (*addr == NULL) {

/* Don't call SDL_SetError(): SDL_LoadFunction already did. */

return 0;

}

return 1;

}

/* cast funcs to char* first, to please GCC's strict aliasing rules. */

#define SDL_ALSA_SYM(x) \

if (!load_alsa_sym(#x, (void **) (char *) &ALSA_##x)) return -1

#else

#define SDL_ALSA_SYM(x) ALSA_##x = x

#endif

static int

load_alsa_syms(void)

{

SDL_ALSA_SYM(snd_pcm_open);

SDL_ALSA_SYM(snd_pcm_close);

SDL_ALSA_SYM(snd_pcm_writei);

SDL_ALSA_SYM(snd_pcm_prepare);

SDL_ALSA_SYM(snd_pcm_drain);

SDL_ALSA_SYM(snd_strerror);

SDL_ALSA_SYM(snd_pcm_hw_params_sizeof);

SDL_ALSA_SYM(snd_pcm_sw_params_sizeof);

SDL_ALSA_SYM(snd_pcm_hw_params_any);

SDL_ALSA_SYM(snd_pcm_hw_params_set_access);

SDL_ALSA_SYM(snd_pcm_hw_params_set_format);

SDL_ALSA_SYM(snd_pcm_hw_params_set_channels);

SDL_ALSA_SYM(snd_pcm_hw_params_get_channels);

SDL_ALSA_SYM(snd_pcm_hw_params_set_rate_near);

SDL_ALSA_SYM(snd_pcm_hw_params_set_period_size_near);

SDL_ALSA_SYM(snd_pcm_hw_params_get_period_size);

SDL_ALSA_SYM(snd_pcm_hw_params_set_periods_near);

SDL_ALSA_SYM(snd_pcm_hw_params_get_periods);

SDL_ALSA_SYM(snd_pcm_hw_params_set_buffer_size_near);

SDL_ALSA_SYM(snd_pcm_hw_params_get_buffer_size);

SDL_ALSA_SYM(snd_pcm_hw_params);

SDL_ALSA_SYM(snd_pcm_sw_params_current);

SDL_ALSA_SYM(snd_pcm_sw_params_set_start_threshold);

SDL_ALSA_SYM(snd_pcm_sw_params);

SDL_ALSA_SYM(snd_pcm_nonblock);

return 0;

}

#undef SDL_ALSA_SYM

#ifdef SDL_AUDIO_DRIVER_ALSA_DYNAMIC

static void

UnloadALSALibrary(void)

{

alsa_handle = NULL;

}

}

static int

LoadALSALibrary(void)

{

int retval = 0;

if (alsa_handle == NULL) {

if (alsa_handle == NULL) {

retval = -1;

} else {

retval = load_alsa_syms();

if (retval < 0) {

UnloadALSALibrary();

}

}

}

return retval;

}

#else

static void

UnloadALSALibrary(void)

{

}

static int

LoadALSALibrary(void)

{

}

static const char *

get_audio_device(int channels)

const char *device;

device = SDL_getenv("AUDIODEV"); /* Is there a standard variable name? */

if (device == NULL) {

switch (channels) {

case 6:

device = "plug:surround51";

break;

case 4:

device = "plug:surround40";

break;

default:

device = "default";

break;

}

}

return device;

}

/* This function waits until it is possible to write a full sound buffer */

}

/*

* http://bugzilla.libsdl.org/show_bug.cgi?id=110

* "For Linux ALSA, this is FL-FR-RL-RR-C-LFE

* and for Windows DirectX [and CoreAudio], this is FL-FR-C-LFE-RL-RR"

*/

#define SWIZ6(T) \

T tmp; \

tmp = ptr[2]; ptr[2] = ptr[4]; ptr[4] = tmp; \

tmp = ptr[3]; ptr[3] = ptr[5]; ptr[5] = tmp; \

}

static __inline__ void

swizzle_alsa_channels_6_64bit(_THIS)

{

SWIZ6(Uint64);

}

static __inline__ void

swizzle_alsa_channels_6_32bit(_THIS)

{

SWIZ6(Uint32);

}

static __inline__ void

swizzle_alsa_channels_6_16bit(_THIS)

{

SWIZ6(Uint16);

}

static __inline__ void

swizzle_alsa_channels_6_8bit(_THIS)

{

SWIZ6(Uint8);

}

#undef SWIZ6

/*

* Called right before feeding this->hidden->mixbuf to the hardware. Swizzle

* channels from Windows/Mac order to the format alsalib will want.

static __inline__ void

swizzle_alsa_channels(_THIS)

{

if (this->spec.channels == 6) {

if (fmtsize == 16)

swizzle_alsa_channels_6_16bit(this);

else if (fmtsize == 8)

swizzle_alsa_channels_6_8bit(this);

else if (fmtsize == 32)

swizzle_alsa_channels_6_32bit(this);

else if (fmtsize == 64)

swizzle_alsa_channels_6_64bit(this);

}

/* !!! FIXME: update this for 7.1 if needed, later. */

}

const Uint8 *sample_buf = (const Uint8 *) this->hidden->mixbuf;

const int frame_size = (((int) (this->spec.format & 0xFF)) / 8) *

this->spec.channels;

snd_pcm_uframes_t frames_left = ((snd_pcm_uframes_t) this->spec.samples);

swizzle_alsa_channels(this);

while ( frames_left > 0 && this->enabled ) {

/* !!! FIXME: This works, but needs more testing before going live */

/*ALSA_snd_pcm_wait(this->hidden->pcm_handle, -1);*/

if (status < 0) {

if (status == -EAGAIN) {

/* Apparently snd_pcm_recover() doesn't handle this case -

does it assume snd_pcm_wait() above? */

SDL_Delay(1);

continue;

}

if (status < 0) {

/* Hmm, not much we can do - abort */

fprintf(stderr, "ALSA write failed (unrecoverable): %s\n",

ALSA_snd_strerror(status));

this->enabled = 0;

return;

}

continue;

}

sample_buf += status * frame_size;

frames_left -= status;

}

}

if (this->hidden != NULL) {

if (this->hidden->mixbuf != NULL) {

SDL_FreeAudioMem(this->hidden->mixbuf);

this->hidden->mixbuf = NULL;

}

if (this->hidden->pcm_handle) {

ALSA_snd_pcm_drain(this->hidden->pcm_handle);

ALSA_snd_pcm_close(this->hidden->pcm_handle);

this->hidden->pcm_handle = NULL;

}

SDL_free(this->hidden);

this->hidden = NULL;

}

static int

ALSA_finalize_hardware(_THIS, snd_pcm_hw_params_t *hwparams, int override)

{

int status;

snd_pcm_uframes_t bufsize;

/* "set" the hardware with the desired parameters */

status = ALSA_snd_pcm_hw_params(this->hidden->pcm_handle, hwparams);

if ( status < 0 ) {

return(-1);

}

/* Get samples for the actual buffer size */

status = ALSA_snd_pcm_hw_params_get_buffer_size(hwparams, &bufsize);

if ( status < 0 ) {

return(-1);

}

if ( !override && bufsize != this->spec.samples * 2 ) {

return(-1);

}

/* !!! FIXME: Is this safe to do? */

this->spec.samples = bufsize / 2;

/* This is useful for debugging */

if ( SDL_getenv("SDL_AUDIO_ALSA_DEBUG") ) {

snd_pcm_uframes_t persize = 0;

unsigned int periods = 0;

ALSA_snd_pcm_hw_params_get_period_size(hwparams, &persize, NULL);

ALSA_snd_pcm_hw_params_get_periods(hwparams, &periods, NULL);

fprintf(stderr,

"ALSA: period size = %ld, periods = %u, buffer size = %lu\n",

persize, periods, bufsize);

}

return(0);

}

static int

ALSA_set_period_size(_THIS, snd_pcm_hw_params_t *params, int override)

{

const char *env;

int status;

snd_pcm_hw_params_t *hwparams;

snd_pcm_uframes_t frames;

unsigned int periods;

/* Copy the hardware parameters for this setup */

snd_pcm_hw_params_alloca(&hwparams);

ALSA_snd_pcm_hw_params_copy(hwparams, params);

if ( !override ) {

env = SDL_getenv("SDL_AUDIO_ALSA_SET_PERIOD_SIZE");

if ( env ) {

override = SDL_atoi(env);

if ( override == 0 ) {

return(-1);

}

}

}

frames = this->spec.samples;

status = ALSA_snd_pcm_hw_params_set_period_size_near(

this->hidden->pcm_handle, hwparams, &frames, NULL);

if ( status < 0 ) {

return(-1);

}

periods = 2;

status = ALSA_snd_pcm_hw_params_set_periods_near(

this->hidden->pcm_handle, hwparams, &periods, NULL);

if ( status < 0 ) {

return(-1);

}

return ALSA_finalize_hardware(this, hwparams, override);

}

static int

ALSA_set_buffer_size(_THIS, snd_pcm_hw_params_t *params, int override)

{

const char *env;

int status;

snd_pcm_hw_params_t *hwparams;

snd_pcm_uframes_t frames;

/* Copy the hardware parameters for this setup */

snd_pcm_hw_params_alloca(&hwparams);

ALSA_snd_pcm_hw_params_copy(hwparams, params);

if ( !override ) {

env = SDL_getenv("SDL_AUDIO_ALSA_SET_BUFFER_SIZE");

if ( env ) {

override = SDL_atoi(env);

if ( override == 0 ) {

return(-1);

}

}

}

frames = this->spec.samples * 2;

status = ALSA_snd_pcm_hw_params_set_buffer_size_near(

this->hidden->pcm_handle, hwparams, &frames);

if ( status < 0 ) {

return(-1);

}

return ALSA_finalize_hardware(this, hwparams, override);

}

int status = 0;

snd_pcm_t *pcm_handle = NULL;

snd_pcm_hw_params_t *hwparams = NULL;

snd_pcm_sw_params_t *swparams = NULL;

snd_pcm_format_t format = 0;

SDL_AudioFormat test_format = 0;

unsigned int rate = 0;

unsigned int channels = 0;

/* Initialize all variables that we clean on shutdown */

this->hidden = (struct SDL_PrivateAudioData *)

if (this->hidden == NULL) {

SDL_OutOfMemory();

return 0;

}

SDL_memset(this->hidden, 0, (sizeof *this->hidden));

/* Open the audio device */

/* Name of device should depend on # channels in spec */

status = ALSA_snd_pcm_open(&pcm_handle,

get_audio_device(this->spec.channels),

SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);

if (status < 0) {

ALSA_CloseDevice(this);

SDL_SetError("ALSA: Couldn't open audio device: %s",

ALSA_snd_strerror(status));

return 0;

}

this->hidden->pcm_handle = pcm_handle;

/* Figure out what the hardware is capable of */

snd_pcm_hw_params_alloca(&hwparams);

ALSA_CloseDevice(this);

SDL_SetError("ALSA: Couldn't get hardware config: %s",

ALSA_snd_strerror(status));

return 0;

}

/* SDL only uses interleaved sample output */

status = ALSA_snd_pcm_hw_params_set_access(pcm_handle, hwparams,

SND_PCM_ACCESS_RW_INTERLEAVED);

ALSA_CloseDevice(this);

SDL_SetError("ALSA: Couldn't set interleaved access: %s",

ALSA_snd_strerror(status));

return 0;

}

/* Try for a closest match on audio format */

status = -1;

switch (test_format) {

case AUDIO_U8:

format = SND_PCM_FORMAT_U8;

break;

case AUDIO_S8:

format = SND_PCM_FORMAT_S8;

break;

case AUDIO_S16LSB:

format = SND_PCM_FORMAT_S16_LE;

break;

case AUDIO_S16MSB:

format = SND_PCM_FORMAT_S16_BE;

break;

case AUDIO_U16LSB:

format = SND_PCM_FORMAT_U16_LE;

break;

case AUDIO_U16MSB:

format = SND_PCM_FORMAT_U16_BE;

break;

break;

case AUDIO_S32MSB:

break;

case AUDIO_F32LSB:

format = SND_PCM_FORMAT_FLOAT_LE;

break;

case AUDIO_F32MSB:

format = SND_PCM_FORMAT_FLOAT_BE;

break;

break;

}

status = ALSA_snd_pcm_hw_params_set_format(pcm_handle,

hwparams, format);

}

if (status < 0) {

test_format = SDL_NextAudioFormat();

}

}

if (status < 0) {

ALSA_CloseDevice(this);

SDL_SetError("ALSA: Couldn't find any hardware audio formats");

return 0;

/* Set the number of channels */

status = ALSA_snd_pcm_hw_params_set_channels(pcm_handle, hwparams,

this->spec.channels);

status = ALSA_snd_pcm_hw_params_get_channels(hwparams, &channels);

if (status < 0) {

ALSA_CloseDevice(this);

SDL_SetError("ALSA: Couldn't set audio channels");

return 0;

}

/* Set the audio rate */

ALSA_CloseDevice(this);

SDL_SetError("ALSA: Couldn't set audio frequency: %s",

ALSA_snd_strerror(status));

return 0;

/* Set the buffer size, in samples */

if ( ALSA_set_period_size(this, hwparams, 0) < 0 &&

ALSA_set_buffer_size(this, hwparams, 0) < 0 ) {

/* Failed to set desired buffer size, do the best you can... */

if ( ALSA_set_period_size(this, hwparams, 1) < 0 ) {

ALSA_CloseDevice(this);

SDL_SetError("Couldn't set hardware audio parameters: %s", ALSA_snd_strerror(status));

return(-1);

}

/* Set the software parameters */

snd_pcm_sw_params_alloca(&swparams);

ALSA_CloseDevice(this);

SDL_SetError("ALSA: Couldn't get software config: %s",

ALSA_snd_strerror(status));

return 0;

ALSA_CloseDevice(this);

SDL_SetError("ALSA: Couldn't set start threshold: %s",

ALSA_snd_strerror(status));

return 0;

ALSA_snd_strerror(status));

return 0;