SDL_alsa_audio.c
1
2
/*
SDL - Simple DirectMedia Layer
3
Copyright (C) 1997-2004 Sam Lantinga
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
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
20
slouken@libsdl.org
21
22
23
24
25
26
27
*/
/* Allow access to a raw mixing buffer */
#include <sys/types.h>
28
#include <signal.h> /* For kill() */
29
30
#include "SDL_timer.h"
31
32
33
#include "SDL_audio.h"
#include "../SDL_audiomem.h"
#include "../SDL_audio_c.h"
34
35
#include "SDL_alsa_audio.h"
36
#ifdef SDL_AUDIO_DRIVER_ALSA_DYNAMIC
37
38
39
40
41
42
43
44
#include <dlfcn.h>
#include "SDL_name.h"
#include "SDL_loadso.h"
#else
#define SDL_NAME(X) X
#endif
45
46
47
/* The tag name used by ALSA audio */
#define DRIVER_NAME "alsa"
48
/* The default ALSA audio driver */
49
#define DEFAULT_DEVICE "default"
50
51
/* Audio driver functions */
52
53
54
55
56
57
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);
58
#ifdef SDL_AUDIO_DRIVER_ALSA_DYNAMIC
60
static const char *alsa_library = SDL_AUDIO_DRIVER_ALSA_DYNAMIC;
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
static void *alsa_handle = NULL;
static int alsa_loaded = 0;
static int (*SDL_snd_pcm_open)(snd_pcm_t **pcm, const char *name, snd_pcm_stream_t stream, int mode);
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 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);
static unsigned int (*SDL_NAME(snd_pcm_hw_params_set_rate_near))(snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val, int *dir);
static snd_pcm_uframes_t (*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);
static unsigned int (*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))(snd_pcm_t *pcm, snd_pcm_hw_params_t *params);
static int (*SDL_NAME(snd_pcm_nonblock))(snd_pcm_t *pcm, int nonblock);
#define snd_pcm_hw_params_sizeof SDL_NAME(snd_pcm_hw_params_sizeof)
85
/* cast funcs to char* first, to please GCC's strict aliasing rules. */
86
87
88
89
static struct {
const char *name;
void **func;
} alsa_functions[] = {
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
{ "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) },
{ "snd_pcm_hw_params_sizeof", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_sizeof) },
{ "snd_pcm_hw_params_any", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_any) },
{ "snd_pcm_hw_params_set_access", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_access) },
{ "snd_pcm_hw_params_set_format", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_format) },
{ "snd_pcm_hw_params_set_channels", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_channels) },
{ "snd_pcm_hw_params_get_channels", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_get_channels) },
{ "snd_pcm_hw_params_set_rate_near", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_rate_near) },
{ "snd_pcm_hw_params_set_period_size_near", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_period_size_near) },
{ "snd_pcm_hw_params_set_periods_near", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_periods_near) },
{ "snd_pcm_hw_params", (void**)(char*)&SDL_NAME(snd_pcm_hw_params) },
{ "snd_pcm_nonblock", (void**)(char*)&SDL_NAME(snd_pcm_nonblock) },
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
};
static void UnloadALSALibrary(void) {
if (alsa_loaded) {
/* SDL_UnloadObject(alsa_handle);*/
dlclose(alsa_handle);
alsa_handle = NULL;
alsa_loaded = 0;
}
}
static int LoadALSALibrary(void) {
int i, retval = -1;
/* alsa_handle = SDL_LoadObject(alsa_library);*/
alsa_handle = dlopen(alsa_library,RTLD_NOW);
if (alsa_handle) {
alsa_loaded = 1;
retval = 0;
127
for (i = 0; i < SDL_arraysize(alsa_functions); i++) {
128
/* *alsa_functions[i].func = SDL_LoadFunction(alsa_handle,alsa_functions[i].name);*/
129
#if HAVE_DLVSYM
130
*alsa_functions[i].func = dlvsym(alsa_handle,alsa_functions[i].name,"ALSA_0.9");
131
132
133
if (!*alsa_functions[i].func)
#endif
*alsa_functions[i].func = dlsym(alsa_handle,alsa_functions[i].name);
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
if (!*alsa_functions[i].func) {
retval = -1;
UnloadALSALibrary();
break;
}
}
}
return retval;
}
#else
static void UnloadALSALibrary(void) {
return;
}
static int LoadALSALibrary(void) {
return 0;
}
154
#endif /* SDL_AUDIO_DRIVER_ALSA_DYNAMIC */
156
static const char *get_audio_device(int channels)
157
{
158
159
const char *device;
160
device = SDL_getenv("AUDIODEV"); /* Is there a standard variable name? */
161
if ( device == NULL ) {
162
163
164
if (channels == 6) device = "surround51";
else if (channels == 4) device = "surround40";
else device = DEFAULT_DEVICE;
165
166
}
return device;
167
168
169
170
171
172
173
}
/* Audio driver bootstrap functions */
static int Audio_Available(void)
{
int available;
174
int status;
175
176
177
snd_pcm_t *handle;
available = 0;
178
179
180
if (LoadALSALibrary() < 0) {
return available;
}
181
status = SDL_NAME(snd_pcm_open)(&handle, get_audio_device(2), SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
182
183
if ( status >= 0 ) {
available = 1;
184
SDL_NAME(snd_pcm_close)(handle);
185
}
186
UnloadALSALibrary();
187
188
189
190
191
return(available);
}
static void Audio_DeleteDevice(SDL_AudioDevice *device)
{
192
193
SDL_free(device->hidden);
SDL_free(device);
194
UnloadALSALibrary();
195
196
197
198
199
200
201
}
static SDL_AudioDevice *Audio_CreateDevice(int devindex)
{
SDL_AudioDevice *this;
/* Initialize all variables that we clean on shutdown */
202
LoadALSALibrary();
203
this = (SDL_AudioDevice *)SDL_malloc(sizeof(SDL_AudioDevice));
204
if ( this ) {
205
SDL_memset(this, 0, (sizeof *this));
206
this->hidden = (struct SDL_PrivateAudioData *)
207
SDL_malloc((sizeof *this->hidden));
208
209
210
211
}
if ( (this == NULL) || (this->hidden == NULL) ) {
SDL_OutOfMemory();
if ( this ) {
212
SDL_free(this);
213
214
215
}
return(0);
}
216
SDL_memset(this->hidden, 0, (sizeof *this->hidden));
217
218
/* Set the function pointers */
219
220
221
222
223
this->OpenAudio = ALSA_OpenAudio;
this->WaitAudio = ALSA_WaitAudio;
this->PlayAudio = ALSA_PlayAudio;
this->GetAudioBuf = ALSA_GetAudioBuf;
this->CloseAudio = ALSA_CloseAudio;
224
225
226
227
228
229
230
this->free = Audio_DeleteDevice;
return this;
}
AudioBootStrap ALSA_bootstrap = {
231
DRIVER_NAME, "ALSA 0.9 PCM audio",
232
233
234
235
Audio_Available, Audio_CreateDevice
};
/* This function waits until it is possible to write a full sound buffer */
236
static void ALSA_WaitAudio(_THIS)
237
238
239
240
241
242
243
244
245
246
247
248
249
250
{
/* 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 */
if ( kill(parent, 0) < 0 ) {
this->enabled = 0;
}
}
}
}
251
static void ALSA_PlayAudio(_THIS)
252
{
253
254
255
int status;
int sample_len;
signed short *sample_buf;
257
258
259
sample_len = this->spec.samples;
sample_buf = (signed short *)mixbuf;
while ( sample_len > 0 ) {
260
status = SDL_NAME(snd_pcm_writei)(pcm_handle, sample_buf, sample_len);
261
262
if ( status < 0 ) {
if ( status == -EAGAIN ) {
264
265
266
267
continue;
}
if ( status == -ESTRPIPE ) {
do {
269
status = SDL_NAME(snd_pcm_resume)(pcm_handle);
270
271
272
} while ( status == -EAGAIN );
}
if ( status < 0 ) {
273
status = SDL_NAME(snd_pcm_prepare)(pcm_handle);
274
275
276
277
278
}
if ( status < 0 ) {
/* Hmm, not much we can do - abort */
this->enabled = 0;
return;
279
}
280
continue;
281
}
282
283
sample_buf += status * this->spec.channels;
sample_len -= status;
284
285
286
}
}
287
static Uint8 *ALSA_GetAudioBuf(_THIS)
288
{
289
return(mixbuf);
290
291
}
292
static void ALSA_CloseAudio(_THIS)
293
{
294
295
296
if ( mixbuf != NULL ) {
SDL_FreeAudioMem(mixbuf);
mixbuf = NULL;
297
}
298
if ( pcm_handle ) {
299
300
SDL_NAME(snd_pcm_drain)(pcm_handle);
SDL_NAME(snd_pcm_close)(pcm_handle);
301
pcm_handle = NULL;
302
303
304
}
}
305
static int ALSA_OpenAudio(_THIS, SDL_AudioSpec *spec)
306
{
307
308
309
310
311
int status;
snd_pcm_hw_params_t *params;
snd_pcm_format_t format;
snd_pcm_uframes_t frames;
Uint16 test_format;
312
313
/* Open the audio device */
314
315
316
/* Name of device should depend on # channels in spec */
status = SDL_NAME(snd_pcm_open)(&pcm_handle, get_audio_device(spec->channels), SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
317
if ( status < 0 ) {
318
SDL_SetError("Couldn't open audio device: %s", SDL_NAME(snd_strerror)(status));
319
320
321
return(-1);
}
322
323
/* Figure out what the hardware is capable of */
snd_pcm_hw_params_alloca(¶ms);
324
status = SDL_NAME(snd_pcm_hw_params_any)(pcm_handle, params);
325
if ( status < 0 ) {
326
SDL_SetError("Couldn't get hardware config: %s", SDL_NAME(snd_strerror)(status));
327
328
329
ALSA_CloseAudio(this);
return(-1);
}
331
/* SDL only uses interleaved sample output */
332
status = SDL_NAME(snd_pcm_hw_params_set_access)(pcm_handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
333
if ( status < 0 ) {
334
SDL_SetError("Couldn't set interleaved access: %s", SDL_NAME(snd_strerror)(status));
335
336
337
ALSA_CloseAudio(this);
return(-1);
}
338
339
/* Try for a closest match on audio format */
340
status = -1;
341
for ( test_format = SDL_FirstAudioFormat(spec->format);
342
343
test_format && (status < 0); ) {
switch ( test_format ) {
344
case AUDIO_U8:
345
format = SND_PCM_FORMAT_U8;
346
347
break;
case AUDIO_S8:
348
format = SND_PCM_FORMAT_S8;
349
350
break;
case AUDIO_S16LSB:
351
format = SND_PCM_FORMAT_S16_LE;
352
353
break;
case AUDIO_S16MSB:
354
format = SND_PCM_FORMAT_S16_BE;
355
356
break;
case AUDIO_U16LSB:
357
format = SND_PCM_FORMAT_U16_LE;
358
359
break;
case AUDIO_U16MSB:
360
format = SND_PCM_FORMAT_U16_BE;
361
362
break;
default:
363
format = 0;
364
365
break;
}
366
if ( format != 0 ) {
367
status = SDL_NAME(snd_pcm_hw_params_set_format)(pcm_handle, params, format);
368
369
}
if ( status < 0 ) {
370
371
372
test_format = SDL_NextAudioFormat();
}
}
373
if ( status < 0 ) {
374
SDL_SetError("Couldn't find any hardware audio formats");
375
ALSA_CloseAudio(this);
376
377
378
379
return(-1);
}
spec->format = test_format;
380
/* Set the number of channels */
381
status = SDL_NAME(snd_pcm_hw_params_set_channels)(pcm_handle, params, spec->channels);
382
if ( status < 0 ) {
383
status = SDL_NAME(snd_pcm_hw_params_get_channels)(params);
384
385
386
387
388
389
390
if ( (status <= 0) || (status > 2) ) {
SDL_SetError("Couldn't set audio channels");
ALSA_CloseAudio(this);
return(-1);
}
spec->channels = status;
}
392
/* Set the audio rate */
393
status = SDL_NAME(snd_pcm_hw_params_set_rate_near)(pcm_handle, params, spec->freq, NULL);
394
if ( status < 0 ) {
395
SDL_SetError("Couldn't set audio frequency: %s", SDL_NAME(snd_strerror)(status));
396
397
398
399
400
401
402
ALSA_CloseAudio(this);
return(-1);
}
spec->freq = status;
/* Set the buffer size, in samples */
frames = spec->samples;
403
frames = SDL_NAME(snd_pcm_hw_params_set_period_size_near)(pcm_handle, params, frames, NULL);
404
spec->samples = frames;
405
SDL_NAME(snd_pcm_hw_params_set_periods_near)(pcm_handle, params, 2, NULL);
406
407
/* "set" the hardware with the desired parameters */
408
status = SDL_NAME(snd_pcm_hw_params)(pcm_handle, params);
409
if ( status < 0 ) {
410
SDL_SetError("Couldn't set audio parameters: %s", SDL_NAME(snd_strerror)(status));
411
ALSA_CloseAudio(this);
412
413
414
return(-1);
}
415
416
417
418
419
420
421
422
423
/* Calculate the final parameters for this audio specification */
SDL_CalculateAudioSpec(spec);
/* Allocate mixing buffer */
mixlen = spec->size;
mixbuf = (Uint8 *)SDL_AllocAudioMem(mixlen);
if ( mixbuf == NULL ) {
ALSA_CloseAudio(this);
return(-1);
424
}
425
SDL_memset(mixbuf, spec->silence, spec->size);
426
427
428
429
/* Get the parent process id (we're the parent of the audio thread) */
parent = getpid();
430
/* Switch to blocking mode for playback */
431
SDL_NAME(snd_pcm_nonblock)(pcm_handle, 0);
433
434
435
/* We're ready to rock and roll. :-) */
return(0);
}