/
SDL_alsa_audio.c
538 lines (470 loc) · 17.3 KB
1
2
/*
SDL - Simple DirectMedia Layer
3
Copyright (C) 1997-2009 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
#include "SDL_config.h"
23
24
25
26
/* Allow access to a raw mixing buffer */
#include <sys/types.h>
27
#include <signal.h> /* For kill() */
28
29
#include "SDL_timer.h"
30
31
32
#include "SDL_audio.h"
#include "../SDL_audiomem.h"
#include "../SDL_audio_c.h"
33
34
#include "SDL_alsa_audio.h"
35
#ifdef SDL_AUDIO_DRIVER_ALSA_DYNAMIC
36
37
38
39
40
41
42
43
#include <dlfcn.h>
#include "SDL_name.h"
#include "SDL_loadso.h"
#else
#define SDL_NAME(X) X
#endif
44
45
46
/* The tag name used by ALSA audio */
#define DRIVER_NAME "alsa"
47
/* The default ALSA audio driver */
48
#define DEFAULT_DEVICE "default"
49
50
/* Audio driver functions */
51
52
53
54
55
56
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);
57
#ifdef SDL_AUDIO_DRIVER_ALSA_DYNAMIC
58
59
static const char *alsa_library = SDL_AUDIO_DRIVER_ALSA_DYNAMIC;
60
61
62
63
64
65
66
67
68
69
70
71
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);
72
static size_t (*SDL_NAME(snd_pcm_sw_params_sizeof))(void);
73
74
75
76
77
78
79
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);
80
static snd_pcm_sframes_t (*SDL_NAME(snd_pcm_hw_params_get_period_size))(const snd_pcm_hw_params_t *params);
81
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);
82
static int (*SDL_NAME(snd_pcm_hw_params_get_periods))(snd_pcm_hw_params_t *params);
83
static int (*SDL_NAME(snd_pcm_hw_params))(snd_pcm_t *pcm, snd_pcm_hw_params_t *params);
84
85
86
87
88
89
/*
*/
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);
90
static int (*SDL_NAME(snd_pcm_nonblock))(snd_pcm_t *pcm, int nonblock);
91
#define snd_pcm_hw_params_sizeof SDL_NAME(snd_pcm_hw_params_sizeof)
92
#define snd_pcm_sw_params_sizeof SDL_NAME(snd_pcm_sw_params_sizeof)
93
94
/* cast funcs to char* first, to please GCC's strict aliasing rules. */
95
96
97
98
static struct {
const char *name;
void **func;
} alsa_functions[] = {
99
100
101
102
103
104
105
106
{ "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) },
107
{ "snd_pcm_sw_params_sizeof", (void**)(char*)&SDL_NAME(snd_pcm_sw_params_sizeof) },
108
109
110
111
112
113
114
{ "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) },
115
{ "snd_pcm_hw_params_get_period_size", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_get_period_size) },
116
{ "snd_pcm_hw_params_set_periods_near", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_periods_near) },
117
{ "snd_pcm_hw_params_get_periods", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_get_periods) },
118
{ "snd_pcm_hw_params", (void**)(char*)&SDL_NAME(snd_pcm_hw_params) },
119
120
121
122
{ "snd_pcm_sw_params_current", (void**)(char*)&SDL_NAME(snd_pcm_sw_params_current) },
{ "snd_pcm_sw_params_set_start_threshold", (void**)(char*)&SDL_NAME(snd_pcm_sw_params_set_start_threshold) },
{ "snd_pcm_sw_params_set_avail_min", (void**)(char*)&SDL_NAME(snd_pcm_sw_params_set_avail_min) },
{ "snd_pcm_sw_params", (void**)(char*)&SDL_NAME(snd_pcm_sw_params) },
123
{ "snd_pcm_nonblock", (void**)(char*)&SDL_NAME(snd_pcm_nonblock) },
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
};
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;
143
for (i = 0; i < SDL_arraysize(alsa_functions); i++) {
144
/* *alsa_functions[i].func = SDL_LoadFunction(alsa_handle,alsa_functions[i].name);*/
145
#if HAVE_DLVSYM
146
*alsa_functions[i].func = dlvsym(alsa_handle,alsa_functions[i].name,"ALSA_0.9");
147
148
149
if (!*alsa_functions[i].func)
#endif
*alsa_functions[i].func = dlsym(alsa_handle,alsa_functions[i].name);
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
if (!*alsa_functions[i].func) {
retval = -1;
UnloadALSALibrary();
break;
}
}
}
return retval;
}
#else
static void UnloadALSALibrary(void) {
return;
}
static int LoadALSALibrary(void) {
return 0;
}
170
#endif /* SDL_AUDIO_DRIVER_ALSA_DYNAMIC */
171
172
static const char *get_audio_device(int channels)
173
{
174
175
const char *device;
176
device = SDL_getenv("AUDIODEV"); /* Is there a standard variable name? */
177
if ( device == NULL ) {
178
179
180
if (channels == 6) device = "surround51";
else if (channels == 4) device = "surround40";
else device = DEFAULT_DEVICE;
181
182
}
return device;
183
184
185
186
187
188
189
}
/* Audio driver bootstrap functions */
static int Audio_Available(void)
{
int available;
190
int status;
191
192
193
snd_pcm_t *handle;
available = 0;
194
195
196
if (LoadALSALibrary() < 0) {
return available;
}
197
status = SDL_NAME(snd_pcm_open)(&handle, get_audio_device(2), SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
198
199
if ( status >= 0 ) {
available = 1;
200
SDL_NAME(snd_pcm_close)(handle);
201
}
202
UnloadALSALibrary();
203
204
205
206
207
return(available);
}
static void Audio_DeleteDevice(SDL_AudioDevice *device)
{
208
209
SDL_free(device->hidden);
SDL_free(device);
210
UnloadALSALibrary();
211
212
213
214
215
216
217
}
static SDL_AudioDevice *Audio_CreateDevice(int devindex)
{
SDL_AudioDevice *this;
/* Initialize all variables that we clean on shutdown */
218
LoadALSALibrary();
219
this = (SDL_AudioDevice *)SDL_malloc(sizeof(SDL_AudioDevice));
220
if ( this ) {
221
SDL_memset(this, 0, (sizeof *this));
222
this->hidden = (struct SDL_PrivateAudioData *)
223
SDL_malloc((sizeof *this->hidden));
224
225
226
227
}
if ( (this == NULL) || (this->hidden == NULL) ) {
SDL_OutOfMemory();
if ( this ) {
228
SDL_free(this);
229
230
231
}
return(0);
}
232
SDL_memset(this->hidden, 0, (sizeof *this->hidden));
233
234
/* Set the function pointers */
235
236
237
238
239
this->OpenAudio = ALSA_OpenAudio;
this->WaitAudio = ALSA_WaitAudio;
this->PlayAudio = ALSA_PlayAudio;
this->GetAudioBuf = ALSA_GetAudioBuf;
this->CloseAudio = ALSA_CloseAudio;
240
241
242
243
244
245
246
this->free = Audio_DeleteDevice;
return this;
}
AudioBootStrap ALSA_bootstrap = {
247
DRIVER_NAME, "ALSA 0.9 PCM audio",
248
249
250
251
Audio_Available, Audio_CreateDevice
};
/* This function waits until it is possible to write a full sound buffer */
252
static void ALSA_WaitAudio(_THIS)
253
254
255
256
257
258
259
260
261
262
263
264
265
266
{
/* 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;
}
}
}
}
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
/*
* 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 *ptr = (T *) mixbuf; \
const Uint32 count = (this->spec.samples / 6); \
Uint32 i; \
for (i = 0; i < count; i++, ptr += 6) { \
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->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) {
const Uint16 fmtsize = (this->spec.format & 0xFF); /* bits/channel. */
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. */
}
313
static void ALSA_PlayAudio(_THIS)
314
{
315
316
317
int status;
int sample_len;
signed short *sample_buf;
318
319
320
swizzle_alsa_channels(this);
321
322
sample_len = this->spec.samples;
sample_buf = (signed short *)mixbuf;
323
324
while ( sample_len > 0 ) {
325
status = SDL_NAME(snd_pcm_writei)(pcm_handle, sample_buf, sample_len);
326
327
if ( status < 0 ) {
if ( status == -EAGAIN ) {
328
SDL_Delay(1);
329
330
331
332
continue;
}
if ( status == -ESTRPIPE ) {
do {
333
SDL_Delay(1);
334
status = SDL_NAME(snd_pcm_resume)(pcm_handle);
335
336
337
} while ( status == -EAGAIN );
}
if ( status < 0 ) {
338
status = SDL_NAME(snd_pcm_prepare)(pcm_handle);
339
340
341
342
343
}
if ( status < 0 ) {
/* Hmm, not much we can do - abort */
this->enabled = 0;
return;
344
}
345
continue;
346
}
347
348
sample_buf += status * this->spec.channels;
sample_len -= status;
349
350
351
}
}
352
static Uint8 *ALSA_GetAudioBuf(_THIS)
353
{
354
return(mixbuf);
355
356
}
357
static void ALSA_CloseAudio(_THIS)
358
{
359
360
361
if ( mixbuf != NULL ) {
SDL_FreeAudioMem(mixbuf);
mixbuf = NULL;
362
}
363
if ( pcm_handle ) {
364
365
SDL_NAME(snd_pcm_drain)(pcm_handle);
SDL_NAME(snd_pcm_close)(pcm_handle);
366
pcm_handle = NULL;
367
368
369
}
}
370
static int ALSA_OpenAudio(_THIS, SDL_AudioSpec *spec)
371
{
372
int status;
373
374
snd_pcm_hw_params_t *hwparams;
snd_pcm_sw_params_t *swparams;
375
376
377
snd_pcm_format_t format;
snd_pcm_uframes_t frames;
Uint16 test_format;
378
379
/* Open the audio device */
380
381
382
/* 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);
383
if ( status < 0 ) {
384
SDL_SetError("Couldn't open audio device: %s", SDL_NAME(snd_strerror)(status));
385
386
387
return(-1);
}
388
/* Figure out what the hardware is capable of */
389
390
snd_pcm_hw_params_alloca(&hwparams);
status = SDL_NAME(snd_pcm_hw_params_any)(pcm_handle, hwparams);
391
if ( status < 0 ) {
392
SDL_SetError("Couldn't get hardware config: %s", SDL_NAME(snd_strerror)(status));
393
394
395
ALSA_CloseAudio(this);
return(-1);
}
396
397
/* SDL only uses interleaved sample output */
398
status = SDL_NAME(snd_pcm_hw_params_set_access)(pcm_handle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED);
399
if ( status < 0 ) {
400
SDL_SetError("Couldn't set interleaved access: %s", SDL_NAME(snd_strerror)(status));
401
402
403
ALSA_CloseAudio(this);
return(-1);
}
404
405
/* Try for a closest match on audio format */
406
status = -1;
407
for ( test_format = SDL_FirstAudioFormat(spec->format);
408
409
test_format && (status < 0); ) {
switch ( test_format ) {
410
case AUDIO_U8:
411
format = SND_PCM_FORMAT_U8;
412
413
break;
case AUDIO_S8:
414
format = SND_PCM_FORMAT_S8;
415
416
break;
case AUDIO_S16LSB:
417
format = SND_PCM_FORMAT_S16_LE;
418
419
break;
case AUDIO_S16MSB:
420
format = SND_PCM_FORMAT_S16_BE;
421
422
break;
case AUDIO_U16LSB:
423
format = SND_PCM_FORMAT_U16_LE;
424
425
break;
case AUDIO_U16MSB:
426
format = SND_PCM_FORMAT_U16_BE;
427
428
break;
default:
429
format = 0;
430
431
break;
}
432
if ( format != 0 ) {
433
status = SDL_NAME(snd_pcm_hw_params_set_format)(pcm_handle, hwparams, format);
434
435
}
if ( status < 0 ) {
436
437
438
test_format = SDL_NextAudioFormat();
}
}
439
if ( status < 0 ) {
440
SDL_SetError("Couldn't find any hardware audio formats");
441
ALSA_CloseAudio(this);
442
443
444
445
return(-1);
}
spec->format = test_format;
446
/* Set the number of channels */
447
status = SDL_NAME(snd_pcm_hw_params_set_channels)(pcm_handle, hwparams, spec->channels);
448
if ( status < 0 ) {
449
status = SDL_NAME(snd_pcm_hw_params_get_channels)(hwparams);
450
451
452
453
454
455
456
if ( (status <= 0) || (status > 2) ) {
SDL_SetError("Couldn't set audio channels");
ALSA_CloseAudio(this);
return(-1);
}
spec->channels = status;
}
457
458
/* Set the audio rate */
459
status = SDL_NAME(snd_pcm_hw_params_set_rate_near)(pcm_handle, hwparams, spec->freq, NULL);
460
if ( status < 0 ) {
461
SDL_SetError("Couldn't set audio frequency: %s", SDL_NAME(snd_strerror)(status));
462
463
464
465
466
467
468
ALSA_CloseAudio(this);
return(-1);
}
spec->freq = status;
/* Set the buffer size, in samples */
frames = spec->samples;
469
frames = SDL_NAME(snd_pcm_hw_params_set_period_size_near)(pcm_handle, hwparams, frames, NULL);
470
spec->samples = frames;
471
SDL_NAME(snd_pcm_hw_params_set_periods_near)(pcm_handle, hwparams, 2, NULL);
472
473
/* "set" the hardware with the desired parameters */
474
475
476
477
478
479
480
status = SDL_NAME(snd_pcm_hw_params)(pcm_handle, hwparams);
if ( status < 0 ) {
SDL_SetError("Couldn't set hardware audio parameters: %s", SDL_NAME(snd_strerror)(status));
ALSA_CloseAudio(this);
return(-1);
}
481
/* This is useful for debugging... */
483
{ snd_pcm_sframes_t bufsize; int fragments;
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
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);
}
*/
/* Set the software parameters */
snd_pcm_sw_params_alloca(&swparams);
status = SDL_NAME(snd_pcm_sw_params_current)(pcm_handle, swparams);
if ( status < 0 ) {
SDL_SetError("Couldn't get software config: %s", SDL_NAME(snd_strerror)(status));
ALSA_CloseAudio(this);
return(-1);
}
status = SDL_NAME(snd_pcm_sw_params_set_start_threshold)(pcm_handle, swparams, 0);
if ( status < 0 ) {
SDL_SetError("Couldn't set start threshold: %s", SDL_NAME(snd_strerror)(status));
ALSA_CloseAudio(this);
return(-1);
}
status = SDL_NAME(snd_pcm_sw_params_set_avail_min)(pcm_handle, swparams, frames);
if ( status < 0 ) {
SDL_SetError("Couldn't set avail min: %s", SDL_NAME(snd_strerror)(status));
ALSA_CloseAudio(this);
return(-1);
}
status = SDL_NAME(snd_pcm_sw_params)(pcm_handle, swparams);
512
if ( status < 0 ) {
513
SDL_SetError("Couldn't set software audio parameters: %s", SDL_NAME(snd_strerror)(status));
514
ALSA_CloseAudio(this);
515
516
517
return(-1);
}
518
519
520
521
522
523
524
525
526
/* 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);
527
}
528
SDL_memset(mixbuf, spec->silence, spec->size);
529
530
531
532
/* Get the parent process id (we're the parent of the audio thread) */
parent = getpid();
533
/* Switch to blocking mode for playback */
534
SDL_NAME(snd_pcm_nonblock)(pcm_handle, 0);
535
536
537
538
/* We're ready to rock and roll. :-) */
return(0);
}