This repository has been archived by the owner on Feb 11, 2021. It is now read-only.
SDL_alsa_audio.c
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/*
SDL - Simple DirectMedia Layer
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Copyright (C) 1997-2004 Sam Lantinga
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This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with this library; if not, write to the Free
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
Sam Lantinga
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slouken@libsdl.org
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*/
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#include "SDL_config.h"
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/* Allow access to a raw mixing buffer */
#include <sys/types.h>
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#include <signal.h> /* For kill() */
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#include "SDL_timer.h"
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#include "SDL_audio.h"
#include "../SDL_audiomem.h"
#include "../SDL_audio_c.h"
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#include "SDL_alsa_audio.h"
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#ifdef SDL_AUDIO_DRIVER_ALSA_DYNAMIC
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#include <dlfcn.h>
#include "SDL_name.h"
#include "SDL_loadso.h"
#else
#define SDL_NAME(X) X
#endif
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/* The tag name used by ALSA audio */
#define DRIVER_NAME "alsa"
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/* The default ALSA audio driver */
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#define DEFAULT_DEVICE "default"
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/* Audio driver functions */
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static int ALSA_OpenAudio(_THIS, SDL_AudioSpec * spec);
static void ALSA_WaitAudio(_THIS);
static void ALSA_PlayAudio(_THIS);
static Uint8 *ALSA_GetAudioBuf(_THIS);
static void ALSA_CloseAudio(_THIS);
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#ifdef SDL_AUDIO_DRIVER_ALSA_DYNAMIC
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static const char *alsa_library = SDL_AUDIO_DRIVER_ALSA_DYNAMIC;
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static void *alsa_handle = NULL;
static int alsa_loaded = 0;
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static int (*SDL_snd_pcm_open) (snd_pcm_t ** pcm, const char *name,
snd_pcm_stream_t stream, int mode);
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static int (*SDL_NAME(snd_pcm_open)) (snd_pcm_t ** pcm, const char *name,
snd_pcm_stream_t stream, int mode);
static int (*SDL_NAME(snd_pcm_close)) (snd_pcm_t * pcm);
static snd_pcm_sframes_t(*SDL_NAME(snd_pcm_writei)) (snd_pcm_t * pcm,
const void *buffer,
snd_pcm_uframes_t size);
static int (*SDL_NAME(snd_pcm_resume)) (snd_pcm_t * pcm);
static int (*SDL_NAME(snd_pcm_prepare)) (snd_pcm_t * pcm);
static int (*SDL_NAME(snd_pcm_drain)) (snd_pcm_t * pcm);
static const char *(*SDL_NAME(snd_strerror)) (int errnum);
static size_t(*SDL_NAME(snd_pcm_hw_params_sizeof)) (void);
static size_t(*SDL_NAME(snd_pcm_sw_params_sizeof)) (void);
static int (*SDL_NAME(snd_pcm_hw_params_any)) (snd_pcm_t * pcm,
snd_pcm_hw_params_t * params);
static int (*SDL_NAME(snd_pcm_hw_params_set_access)) (snd_pcm_t * pcm,
snd_pcm_hw_params_t *
params,
snd_pcm_access_t
access);
static int (*SDL_NAME(snd_pcm_hw_params_set_format)) (snd_pcm_t * pcm,
snd_pcm_hw_params_t *
params,
snd_pcm_format_t val);
static int (*SDL_NAME(snd_pcm_hw_params_set_channels)) (snd_pcm_t * pcm,
snd_pcm_hw_params_t *
params,
unsigned int val);
static int (*SDL_NAME(snd_pcm_hw_params_get_channels)) (const
snd_pcm_hw_params_t *
params);
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static unsigned int
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(*SDL_NAME(snd_pcm_hw_params_set_rate_near)) (snd_pcm_t *
pcm,
snd_pcm_hw_params_t
* params,
unsigned int val, int *dir);
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static snd_pcm_uframes_t
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(*SDL_NAME(snd_pcm_hw_params_set_period_size_near)) (snd_pcm_t * pcm,
snd_pcm_hw_params_t
* params,
snd_pcm_uframes_t
val, int *dir);
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static snd_pcm_sframes_t
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(*SDL_NAME(snd_pcm_hw_params_get_period_size)) (const
snd_pcm_hw_params_t
* params);
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static unsigned int
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(*SDL_NAME(snd_pcm_hw_params_set_periods_near)) (snd_pcm_t * pcm,
snd_pcm_hw_params_t
* params,
unsigned int val,
int *dir);
static int (*SDL_NAME(snd_pcm_hw_params_get_periods)) (snd_pcm_hw_params_t *
params);
static int (*SDL_NAME(snd_pcm_hw_params)) (snd_pcm_t * pcm,
snd_pcm_hw_params_t * params);
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/*
*/
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static int (*SDL_NAME(snd_pcm_sw_params_current)) (snd_pcm_t * pcm,
snd_pcm_sw_params_t *
swparams);
static int (*SDL_NAME(snd_pcm_sw_params_set_start_threshold)) (snd_pcm_t *
pcm,
snd_pcm_sw_params_t
* params,
snd_pcm_uframes_t
val);
static int (*SDL_NAME(snd_pcm_sw_params_set_avail_min)) (snd_pcm_t * pcm,
snd_pcm_sw_params_t
* params,
snd_pcm_uframes_t
val);
static int (*SDL_NAME(snd_pcm_sw_params)) (snd_pcm_t * pcm,
snd_pcm_sw_params_t * params);
static int (*SDL_NAME(snd_pcm_nonblock)) (snd_pcm_t * pcm, int nonblock);
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#define snd_pcm_hw_params_sizeof SDL_NAME(snd_pcm_hw_params_sizeof)
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#define snd_pcm_sw_params_sizeof SDL_NAME(snd_pcm_sw_params_sizeof)
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/* cast funcs to char* first, to please GCC's strict aliasing rules. */
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static struct
{
const char *name;
void **func;
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} alsa_functions[] = {
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"snd_pcm_open", (void **) (char *) &SDL_NAME(snd_pcm_open)}, {
"snd_pcm_close", (void **) (char *) &SDL_NAME(snd_pcm_close)}, {
"snd_pcm_writei", (void **) (char *) &SDL_NAME(snd_pcm_writei)}, {
"snd_pcm_resume", (void **) (char *) &SDL_NAME(snd_pcm_resume)}, {
"snd_pcm_prepare", (void **) (char *) &SDL_NAME(snd_pcm_prepare)}, {
"snd_pcm_drain", (void **) (char *) &SDL_NAME(snd_pcm_drain)}, {
"snd_strerror", (void **) (char *) &SDL_NAME(snd_strerror)}, {
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"snd_pcm_hw_params_sizeof",
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(void **) (char *) &SDL_NAME(snd_pcm_hw_params_sizeof)}, {
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"snd_pcm_sw_params_sizeof",
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(void **) (char *) &SDL_NAME(snd_pcm_sw_params_sizeof)}, {
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"snd_pcm_hw_params_any",
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(void **) (char *) &SDL_NAME(snd_pcm_hw_params_any)}, {
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"snd_pcm_hw_params_set_access",
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(void **) (char *) &SDL_NAME(snd_pcm_hw_params_set_access)}, {
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"snd_pcm_hw_params_set_format",
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(void **) (char *) &SDL_NAME(snd_pcm_hw_params_set_format)}, {
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"snd_pcm_hw_params_set_channels",
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(void **) (char *) &SDL_NAME(snd_pcm_hw_params_set_channels)}, {
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"snd_pcm_hw_params_get_channels",
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(void **) (char *) &SDL_NAME(snd_pcm_hw_params_get_channels)}, {
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"snd_pcm_hw_params_set_rate_near",
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(void **) (char *) &SDL_NAME(snd_pcm_hw_params_set_rate_near)}, {
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"snd_pcm_hw_params_set_period_size_near", (void **) (char *)
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&SDL_NAME(snd_pcm_hw_params_set_period_size_near)}, {
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"snd_pcm_hw_params_get_period_size",
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(void **) (char *) &SDL_NAME(snd_pcm_hw_params_get_period_size)},
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{
"snd_pcm_hw_params_set_periods_near", (void **) (char *)
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&SDL_NAME(snd_pcm_hw_params_set_periods_near)}, {
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"snd_pcm_hw_params_get_periods",
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(void **) (char *) &SDL_NAME(snd_pcm_hw_params_get_periods)}, {
"snd_pcm_hw_params", (void **) (char *) &SDL_NAME(snd_pcm_hw_params)}, {
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"snd_pcm_sw_params_current",
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(void **) (char *) &SDL_NAME(snd_pcm_sw_params_current)}, {
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"snd_pcm_sw_params_set_start_threshold", (void **) (char *)
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&SDL_NAME(snd_pcm_sw_params_set_start_threshold)}, {
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"snd_pcm_sw_params_set_avail_min",
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(void **) (char *) &SDL_NAME(snd_pcm_sw_params_set_avail_min)}, {
"snd_pcm_sw_params", (void **) (char *) &SDL_NAME(snd_pcm_sw_params)}, {
"snd_pcm_nonblock", (void **) (char *) &SDL_NAME(snd_pcm_nonblock)},};
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static void
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UnloadALSALibrary(void)
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{
if (alsa_loaded) {
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/* SDL_UnloadObject(alsa_handle);*/
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dlclose(alsa_handle);
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alsa_handle = NULL;
alsa_loaded = 0;
}
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LoadALSALibrary(void)
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{
int i, retval = -1;
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/* alsa_handle = SDL_LoadObject(alsa_library);*/
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alsa_handle = dlopen(alsa_library, RTLD_NOW);
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if (alsa_handle) {
alsa_loaded = 1;
retval = 0;
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for (i = 0; i < SDL_arraysize(alsa_functions); i++) {
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/* *alsa_functions[i].func = SDL_LoadFunction(alsa_handle,alsa_functions[i].name);*/
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#if HAVE_DLVSYM
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*alsa_functions[i].func =
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dlvsym(alsa_handle, alsa_functions[i].name, "ALSA_0.9");
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if (!*alsa_functions[i].func)
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*alsa_functions[i].func =
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dlsym(alsa_handle, alsa_functions[i].name);
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if (!*alsa_functions[i].func) {
retval = -1;
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UnloadALSALibrary();
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break;
}
}
}
return retval;
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}
#else
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UnloadALSALibrary(void)
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LoadALSALibrary(void)
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#endif /* SDL_AUDIO_DRIVER_ALSA_DYNAMIC */
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static const char *
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get_audio_device(int channels)
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{
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const char *device;
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device = SDL_getenv("AUDIODEV"); /* Is there a standard variable name? */
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if (device == NULL) {
if (channels == 6)
device = "surround51";
else if (channels == 4)
device = "surround40";
else
device = DEFAULT_DEVICE;
}
return device;
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}
/* Audio driver bootstrap functions */
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Audio_Available(void)
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{
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int available;
int status;
snd_pcm_t *handle;
available = 0;
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if (LoadALSALibrary() < 0) {
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return available;
}
status =
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SDL_NAME(snd_pcm_open) (&handle, get_audio_device(2),
SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
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if (status >= 0) {
available = 1;
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SDL_NAME(snd_pcm_close) (handle);
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UnloadALSALibrary();
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return (available);
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}
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Audio_DeleteDevice(SDL_AudioDevice * device)
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{
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SDL_free(device->hidden);
SDL_free(device);
UnloadALSALibrary();
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}
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static SDL_AudioDevice *
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Audio_CreateDevice(int devindex)
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{
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SDL_AudioDevice *this;
/* Initialize all variables that we clean on shutdown */
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LoadALSALibrary();
this = (SDL_AudioDevice *) SDL_malloc(sizeof(SDL_AudioDevice));
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SDL_memset(this, 0, (sizeof *this));
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this->hidden = (struct SDL_PrivateAudioData *)
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SDL_malloc((sizeof *this->hidden));
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}
if ((this == NULL) || (this->hidden == NULL)) {
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SDL_OutOfMemory();
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SDL_free(this);
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}
return (0);
}
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SDL_memset(this->hidden, 0, (sizeof *this->hidden));
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/* Set the function pointers */
this->OpenAudio = ALSA_OpenAudio;
this->WaitAudio = ALSA_WaitAudio;
this->PlayAudio = ALSA_PlayAudio;
this->GetAudioBuf = ALSA_GetAudioBuf;
this->CloseAudio = ALSA_CloseAudio;
this->free = Audio_DeleteDevice;
return this;
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}
AudioBootStrap ALSA_bootstrap = {
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DRIVER_NAME, "ALSA 0.9 PCM audio",
Audio_Available, Audio_CreateDevice
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};
/* This function waits until it is possible to write a full sound buffer */
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ALSA_WaitAudio(_THIS)
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{
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/* Check to see if the thread-parent process is still alive */
{
static int cnt = 0;
/* Note that this only works with thread implementations
that use a different process id for each thread.
*/
if (parent && (((++cnt) % 10) == 0)) { /* Check every 10 loops */
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if (kill(parent, 0) < 0) {
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this->enabled = 0;
}
}
}
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}
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ALSA_PlayAudio(_THIS)
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{
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int status;
int sample_len;
signed short *sample_buf;
sample_len = this->spec.samples;
sample_buf = (signed short *) mixbuf;
while (sample_len > 0) {
status =
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SDL_NAME(snd_pcm_writei) (pcm_handle, sample_buf, sample_len);
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if (status < 0) {
if (status == -EAGAIN) {
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SDL_Delay(1);
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continue;
}
if (status == -ESTRPIPE) {
do {
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SDL_Delay(1);
status = SDL_NAME(snd_pcm_resume) (pcm_handle);
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}
while (status == -EAGAIN);
}
if (status < 0) {
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status = SDL_NAME(snd_pcm_prepare) (pcm_handle);
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}
if (status < 0) {
/* Hmm, not much we can do - abort */
this->enabled = 0;
return;
}
continue;
}
sample_buf += status * this->spec.channels;
sample_len -= status;
}
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}
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ALSA_GetAudioBuf(_THIS)
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{
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return (mixbuf);
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}
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ALSA_CloseAudio(_THIS)
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{
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if (mixbuf != NULL) {
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SDL_FreeAudioMem(mixbuf);
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mixbuf = NULL;
}
if (pcm_handle) {
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SDL_NAME(snd_pcm_drain) (pcm_handle);
SDL_NAME(snd_pcm_close) (pcm_handle);
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pcm_handle = NULL;
}
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}
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ALSA_OpenAudio(_THIS, SDL_AudioSpec * spec)
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{
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int status;
snd_pcm_hw_params_t *hwparams;
snd_pcm_sw_params_t *swparams;
snd_pcm_format_t format;
snd_pcm_uframes_t frames;
Uint16 test_format;
/* Open the audio device */
/* Name of device should depend on # channels in spec */
status =
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SDL_NAME(snd_pcm_open) (&pcm_handle,
get_audio_device(spec->channels),
SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
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if (status < 0) {
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SDL_SetError("Couldn't open audio device: %s",
SDL_NAME(snd_strerror) (status));
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return (-1);
}
/* Figure out what the hardware is capable of */
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snd_pcm_hw_params_alloca(&hwparams);
status = SDL_NAME(snd_pcm_hw_params_any) (pcm_handle, hwparams);
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if (status < 0) {
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SDL_SetError("Couldn't get hardware config: %s",
SDL_NAME(snd_strerror) (status));
ALSA_CloseAudio(this);
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return (-1);
}
/* SDL only uses interleaved sample output */
status =
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SDL_NAME(snd_pcm_hw_params_set_access) (pcm_handle, hwparams,
SND_PCM_ACCESS_RW_INTERLEAVED);
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if (status < 0) {
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SDL_SetError("Couldn't set interleaved access: %s",
SDL_NAME(snd_strerror) (status));
ALSA_CloseAudio(this);
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return (-1);
}
/* Try for a closest match on audio format */
status = -1;
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for (test_format = SDL_FirstAudioFormat(spec->format);
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test_format && (status < 0);) {
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;
default:
format = 0;
break;
}
if (format != 0) {
status =
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SDL_NAME(snd_pcm_hw_params_set_format) (pcm_handle,
hwparams, format);
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}
if (status < 0) {
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test_format = SDL_NextAudioFormat();
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}
}
if (status < 0) {
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SDL_SetError("Couldn't find any hardware audio formats");
ALSA_CloseAudio(this);
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return (-1);
}
spec->format = test_format;
/* Set the number of channels */
status =
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SDL_NAME(snd_pcm_hw_params_set_channels) (pcm_handle, hwparams,
spec->channels);
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if (status < 0) {
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status = SDL_NAME(snd_pcm_hw_params_get_channels) (hwparams);
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if ((status <= 0) || (status > 2)) {
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SDL_SetError("Couldn't set audio channels");
ALSA_CloseAudio(this);
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return (-1);
}
spec->channels = status;
}
/* Set the audio rate */
status =
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SDL_NAME(snd_pcm_hw_params_set_rate_near) (pcm_handle, hwparams,
spec->freq, NULL);
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if (status < 0) {
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SDL_SetError("Couldn't set audio frequency: %s",
SDL_NAME(snd_strerror) (status));
ALSA_CloseAudio(this);
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return (-1);
}
spec->freq = status;
/* Set the buffer size, in samples */
frames = spec->samples;
frames =
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SDL_NAME(snd_pcm_hw_params_set_period_size_near) (pcm_handle,
hwparams, frames,
NULL);
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spec->samples = frames;
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SDL_NAME(snd_pcm_hw_params_set_periods_near) (pcm_handle, hwparams, 2,
NULL);
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/* "set" the hardware with the desired parameters */
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status = SDL_NAME(snd_pcm_hw_params) (pcm_handle, hwparams);
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if (status < 0) {
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SDL_SetError("Couldn't set hardware audio parameters: %s",
SDL_NAME(snd_strerror) (status));
ALSA_CloseAudio(this);
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return (-1);
}
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/* This is useful for debugging... */
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/*
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{ snd_pcm_sframes_t bufsize; int fragments;
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bufsize = SDL_NAME(snd_pcm_hw_params_get_period_size)(hwparams);
fragments = SDL_NAME(snd_pcm_hw_params_get_periods)(hwparams);
fprintf(stderr, "ALSA: bufsize = %ld, fragments = %d\n", bufsize, fragments);
}
*/
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/* Set the software parameters */
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snd_pcm_sw_params_alloca(&swparams);
status = SDL_NAME(snd_pcm_sw_params_current) (pcm_handle, swparams);
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if (status < 0) {
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SDL_SetError("Couldn't get software config: %s",
SDL_NAME(snd_strerror) (status));
ALSA_CloseAudio(this);
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return (-1);
}
status =
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SDL_NAME(snd_pcm_sw_params_set_start_threshold) (pcm_handle,
swparams, 0);
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if (status < 0) {
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SDL_SetError("Couldn't set start threshold: %s",
SDL_NAME(snd_strerror) (status));
ALSA_CloseAudio(this);
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return (-1);
}
status =
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SDL_NAME(snd_pcm_sw_params_set_avail_min) (pcm_handle, swparams,
frames);
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if (status < 0) {
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SDL_SetError("Couldn't set avail min: %s",
SDL_NAME(snd_strerror) (status));
ALSA_CloseAudio(this);
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return (-1);
}
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status = SDL_NAME(snd_pcm_sw_params) (pcm_handle, swparams);
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if (status < 0) {
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SDL_SetError("Couldn't set software audio parameters: %s",
SDL_NAME(snd_strerror) (status));
ALSA_CloseAudio(this);
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return (-1);
}
/* Calculate the final parameters for this audio specification */
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SDL_CalculateAudioSpec(spec);
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/* Allocate mixing buffer */
mixlen = spec->size;
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mixbuf = (Uint8 *) SDL_AllocAudioMem(mixlen);
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if (mixbuf == NULL) {
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ALSA_CloseAudio(this);
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return (-1);
}
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SDL_memset(mixbuf, spec->silence, spec->size);
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/* Get the parent process id (we're the parent of the audio thread) */
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parent = getpid();
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/* Switch to blocking mode for playback */
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SDL_NAME(snd_pcm_nonblock) (pcm_handle, 0);
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/* We're ready to rock and roll. :-) */
return (0);
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}
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/* vi: set ts=4 sw=4 expandtab: */