1 /*
2 SDL - Simple DirectMedia Layer
3 Copyright (C) 1997-2004 Sam Lantinga
4
5 This library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Library General Public
7 License as published by the Free Software Foundation; either
8 version 2 of the License, or (at your option) any later version.
9
10 This library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Library General Public License for more details.
14
15 You should have received a copy of the GNU Library General Public
16 License along with this library; if not, write to the Free
17 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18
19 Sam Lantinga
20 slouken@libsdl.org
21 */
22 #include "SDL_config.h"
23
24 /* Allow access to a raw mixing buffer */
25
26 #include <sys/types.h>
27 #include <signal.h> /* For kill() */
28
29 #include "SDL_timer.h"
30 #include "SDL_audio.h"
31 #include "../SDL_audiomem.h"
32 #include "../SDL_audio_c.h"
33 #include "SDL_alsa_audio.h"
34
35 #ifdef SDL_AUDIO_DRIVER_ALSA_DYNAMIC
36 #include <dlfcn.h>
37 #include "SDL_name.h"
38 #include "SDL_loadso.h"
39 #else
40 #define SDL_NAME(X) X
41 #endif
42
43
44 /* The tag name used by ALSA audio */
45 #define DRIVER_NAME "alsa"
46
47 /* The default ALSA audio driver */
48 #define DEFAULT_DEVICE "default"
49
50 /* Audio driver functions */
51 static int ALSA_OpenAudio(_THIS, SDL_AudioSpec *spec);
52 static void ALSA_WaitAudio(_THIS);
53 static void ALSA_PlayAudio(_THIS);
54 static Uint8 *ALSA_GetAudioBuf(_THIS);
55 static void ALSA_CloseAudio(_THIS);
56
57 #ifdef SDL_AUDIO_DRIVER_ALSA_DYNAMIC
58
59 static const char *alsa_library = SDL_AUDIO_DRIVER_ALSA_DYNAMIC;
60 static void *alsa_handle = NULL;
61 static int alsa_loaded = 0;
62
63 static int (*SDL_snd_pcm_open)(snd_pcm_t **pcm, const char *name, snd_pcm_stream_t stream, int mode);
64 static int (*SDL_NAME(snd_pcm_open))(snd_pcm_t **pcm, const char *name, snd_pcm_stream_t stream, int mode);
65 static int (*SDL_NAME(snd_pcm_close))(snd_pcm_t *pcm);
66 static snd_pcm_sframes_t (*SDL_NAME(snd_pcm_writei))(snd_pcm_t *pcm, const void *buffer, snd_pcm_uframes_t size);
67 static int (*SDL_NAME(snd_pcm_resume))(snd_pcm_t *pcm);
68 static int (*SDL_NAME(snd_pcm_prepare))(snd_pcm_t *pcm);
69 static int (*SDL_NAME(snd_pcm_drain))(snd_pcm_t *pcm);
70 static const char *(*SDL_NAME(snd_strerror))(int errnum);
71 static size_t (*SDL_NAME(snd_pcm_hw_params_sizeof))(void);
72 static size_t (*SDL_NAME(snd_pcm_sw_params_sizeof))(void);
73 static int (*SDL_NAME(snd_pcm_hw_params_any))(snd_pcm_t *pcm, snd_pcm_hw_params_t *params);
74 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);
75 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);
76 static int (*SDL_NAME(snd_pcm_hw_params_set_channels))(snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val);
77 static int (*SDL_NAME(snd_pcm_hw_params_get_channels))(const snd_pcm_hw_params_t *params);
78 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);
79 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 static int (*SDL_NAME(snd_pcm_sw_params_current))(snd_pcm_t *pcm, snd_pcm_sw_params_t *swparams);
87 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);
88 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);
89 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 static struct {
96 const char *name;
97 void **func;
98 } alsa_functions[] = {
99 { "snd_pcm_open", (void**)(char*)&SDL_NAME(snd_pcm_open) },
100 { "snd_pcm_close", (void**)(char*)&SDL_NAME(snd_pcm_close) },
101 { "snd_pcm_writei", (void**)(char*)&SDL_NAME(snd_pcm_writei) },
102 { "snd_pcm_resume", (void**)(char*)&SDL_NAME(snd_pcm_resume) },
103 { "snd_pcm_prepare", (void**)(char*)&SDL_NAME(snd_pcm_prepare) },
104 { "snd_pcm_drain", (void**)(char*)&SDL_NAME(snd_pcm_drain) },
105 { "snd_strerror", (void**)(char*)&SDL_NAME(snd_strerror) },
106 { "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 { "snd_pcm_hw_params_any", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_any) },
109 { "snd_pcm_hw_params_set_access", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_access) },
110 { "snd_pcm_hw_params_set_format", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_format) },
111 { "snd_pcm_hw_params_set_channels", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_channels) },
112 { "snd_pcm_hw_params_get_channels", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_get_channels) },
113 { "snd_pcm_hw_params_set_rate_near", (void**)(char*)&SDL_NAME(snd_pcm_hw_params_set_rate_near) },
114 { "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 { "snd_pcm_sw_params_current", (void**)(char*)&SDL_NAME(snd_pcm_sw_params_current) },
120 { "snd_pcm_sw_params_set_start_threshold", (void**)(char*)&SDL_NAME(snd_pcm_sw_params_set_start_threshold) },
121 { "snd_pcm_sw_params_set_avail_min", (void**)(char*)&SDL_NAME(snd_pcm_sw_params_set_avail_min) },
122 { "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
UnloadALSALibrary(void)126 static void UnloadALSALibrary(void) {
127 if (alsa_loaded) {
128 /* SDL_UnloadObject(alsa_handle);*/
129 dlclose(alsa_handle);
130 alsa_handle = NULL;
131 alsa_loaded = 0;
132 }
133 }
134
LoadALSALibrary(void)135 static int LoadALSALibrary(void) {
136 int i, retval = -1;
137
138 /* alsa_handle = SDL_LoadObject(alsa_library);*/
139 alsa_handle = dlopen(alsa_library,RTLD_NOW);
140 if (alsa_handle) {
141 alsa_loaded = 1;
142 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 if (!*alsa_functions[i].func)
148 #endif
149 *alsa_functions[i].func = dlsym(alsa_handle,alsa_functions[i].name);
150 if (!*alsa_functions[i].func) {
151 retval = -1;
152 UnloadALSALibrary();
153 break;
154 }
155 }
156 }
157 return retval;
158 }
159
160 #else
161
UnloadALSALibrary(void)162 static void UnloadALSALibrary(void) {
163 return;
164 }
165
LoadALSALibrary(void)166 static int LoadALSALibrary(void) {
167 return 0;
168 }
169
170 #endif /* SDL_AUDIO_DRIVER_ALSA_DYNAMIC */
171
get_audio_device(int channels)172 static const char *get_audio_device(int channels)
173 {
174 const char *device;
175
176 device = SDL_getenv("AUDIODEV"); /* Is there a standard variable name? */
177 if ( device == NULL ) {
178 if (channels == 6) device = "surround51";
179 else if (channels == 4) device = "surround40";
180 else device = DEFAULT_DEVICE;
181 }
182 return device;
183 }
184
185 /* Audio driver bootstrap functions */
186
Audio_Available(void)187 static int Audio_Available(void)
188 {
189 int available;
190 int status;
191 snd_pcm_t *handle;
192
193 available = 0;
194 if (LoadALSALibrary() < 0) {
195 return available;
196 }
197 status = SDL_NAME(snd_pcm_open)(&handle, get_audio_device(2), SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
198 if ( status >= 0 ) {
199 available = 1;
200 SDL_NAME(snd_pcm_close)(handle);
201 }
202 UnloadALSALibrary();
203 return(available);
204 }
205
Audio_DeleteDevice(SDL_AudioDevice * device)206 static void Audio_DeleteDevice(SDL_AudioDevice *device)
207 {
208 SDL_free(device->hidden);
209 SDL_free(device);
210 UnloadALSALibrary();
211 }
212
Audio_CreateDevice(int devindex)213 static SDL_AudioDevice *Audio_CreateDevice(int devindex)
214 {
215 SDL_AudioDevice *this;
216
217 /* 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 if ( (this == NULL) || (this->hidden == NULL) ) {
226 SDL_OutOfMemory();
227 if ( this ) {
228 SDL_free(this);
229 }
230 return(0);
231 }
232 SDL_memset(this->hidden, 0, (sizeof *this->hidden));
233
234 /* Set the function pointers */
235 this->OpenAudio = ALSA_OpenAudio;
236 this->WaitAudio = ALSA_WaitAudio;
237 this->PlayAudio = ALSA_PlayAudio;
238 this->GetAudioBuf = ALSA_GetAudioBuf;
239 this->CloseAudio = ALSA_CloseAudio;
240
241 this->free = Audio_DeleteDevice;
242
243 return this;
244 }
245
246 AudioBootStrap ALSA_bootstrap = {
247 DRIVER_NAME, "ALSA 0.9 PCM audio",
248 Audio_Available, Audio_CreateDevice
249 };
250
251 /* This function waits until it is possible to write a full sound buffer */
ALSA_WaitAudio(_THIS)252 static void ALSA_WaitAudio(_THIS)
253 {
254 /* Check to see if the thread-parent process is still alive */
255 { static int cnt = 0;
256 /* Note that this only works with thread implementations
257 that use a different process id for each thread.
258 */
259 if (parent && (((++cnt)%10) == 0)) { /* Check every 10 loops */
260 if ( kill(parent, 0) < 0 ) {
261 this->enabled = 0;
262 }
263 }
264 }
265 }
266
267
268 /*
269 * http://bugzilla.libsdl.org/show_bug.cgi?id=110
270 * "For Linux ALSA, this is FL-FR-RL-RR-C-LFE
271 * and for Windows DirectX [and CoreAudio], this is FL-FR-C-LFE-RL-RR"
272 */
273 #define SWIZ6(T) \
274 T *ptr = (T *) mixbuf; \
275 const Uint32 count = (this->spec.samples / 6); \
276 Uint32 i; \
277 for (i = 0; i < count; i++, ptr += 6) { \
278 T tmp; \
279 tmp = ptr[2]; ptr[2] = ptr[4]; ptr[4] = tmp; \
280 tmp = ptr[3]; ptr[3] = ptr[5]; ptr[5] = tmp; \
281 }
282
swizzle_alsa_channels_6_64bit(_THIS)283 static __inline__ void swizzle_alsa_channels_6_64bit(_THIS) { SWIZ6(Uint64); }
swizzle_alsa_channels_6_32bit(_THIS)284 static __inline__ void swizzle_alsa_channels_6_32bit(_THIS) { SWIZ6(Uint32); }
swizzle_alsa_channels_6_16bit(_THIS)285 static __inline__ void swizzle_alsa_channels_6_16bit(_THIS) { SWIZ6(Uint16); }
swizzle_alsa_channels_6_8bit(_THIS)286 static __inline__ void swizzle_alsa_channels_6_8bit(_THIS) { SWIZ6(Uint8); }
287
288 #undef SWIZ6
289
290
291 /*
292 * Called right before feeding this->mixbuf to the hardware. Swizzle channels
293 * from Windows/Mac order to the format alsalib will want.
294 */
swizzle_alsa_channels(_THIS)295 static __inline__ void swizzle_alsa_channels(_THIS)
296 {
297 if (this->spec.channels == 6) {
298 const Uint16 fmtsize = (this->spec.format & 0xFF); /* bits/channel. */
299 if (fmtsize == 16)
300 swizzle_alsa_channels_6_16bit(this);
301 else if (fmtsize == 8)
302 swizzle_alsa_channels_6_8bit(this);
303 else if (fmtsize == 32)
304 swizzle_alsa_channels_6_32bit(this);
305 else if (fmtsize == 64)
306 swizzle_alsa_channels_6_64bit(this);
307 }
308
309 /* !!! FIXME: update this for 7.1 if needed, later. */
310 }
311
312
ALSA_PlayAudio(_THIS)313 static void ALSA_PlayAudio(_THIS)
314 {
315 int status;
316 int sample_len;
317 signed short *sample_buf;
318
319 swizzle_alsa_channels(this);
320
321 sample_len = this->spec.samples;
322 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 if ( status < 0 ) {
327 if ( status == -EAGAIN ) {
328 SDL_Delay(1);
329 continue;
330 }
331 if ( status == -ESTRPIPE ) {
332 do {
333 SDL_Delay(1);
334 status = SDL_NAME(snd_pcm_resume)(pcm_handle);
335 } while ( status == -EAGAIN );
336 }
337 if ( status < 0 ) {
338 status = SDL_NAME(snd_pcm_prepare)(pcm_handle);
339 }
340 if ( status < 0 ) {
341 /* Hmm, not much we can do - abort */
342 this->enabled = 0;
343 return;
344 }
345 continue;
346 }
347 sample_buf += status * this->spec.channels;
348 sample_len -= status;
349 }
350 }
351
ALSA_GetAudioBuf(_THIS)352 static Uint8 *ALSA_GetAudioBuf(_THIS)
353 {
354 return(mixbuf);
355 }
356
ALSA_CloseAudio(_THIS)357 static void ALSA_CloseAudio(_THIS)
358 {
359 if ( mixbuf != NULL ) {
360 SDL_FreeAudioMem(mixbuf);
361 mixbuf = NULL;
362 }
363 if ( pcm_handle ) {
364 SDL_NAME(snd_pcm_drain)(pcm_handle);
365 SDL_NAME(snd_pcm_close)(pcm_handle);
366 pcm_handle = NULL;
367 }
368 }
369
ALSA_OpenAudio(_THIS,SDL_AudioSpec * spec)370 static int ALSA_OpenAudio(_THIS, SDL_AudioSpec *spec)
371 {
372 int status;
373 snd_pcm_hw_params_t *hwparams;
374 snd_pcm_sw_params_t *swparams;
375 snd_pcm_format_t format;
376 snd_pcm_uframes_t frames;
377 Uint16 test_format;
378
379 /* Open the audio device */
380 /* Name of device should depend on # channels in spec */
381 status = SDL_NAME(snd_pcm_open)(&pcm_handle, get_audio_device(spec->channels), SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
382
383 if ( status < 0 ) {
384 SDL_SetError("Couldn't open audio device: %s", SDL_NAME(snd_strerror)(status));
385 return(-1);
386 }
387
388 /* Figure out what the hardware is capable of */
389 snd_pcm_hw_params_alloca(&hwparams);
390 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 ALSA_CloseAudio(this);
394 return(-1);
395 }
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 ALSA_CloseAudio(this);
402 return(-1);
403 }
404
405 /* Try for a closest match on audio format */
406 status = -1;
407 for ( test_format = SDL_FirstAudioFormat(spec->format);
408 test_format && (status < 0); ) {
409 switch ( test_format ) {
410 case AUDIO_U8:
411 format = SND_PCM_FORMAT_U8;
412 break;
413 case AUDIO_S8:
414 format = SND_PCM_FORMAT_S8;
415 break;
416 case AUDIO_S16LSB:
417 format = SND_PCM_FORMAT_S16_LE;
418 break;
419 case AUDIO_S16MSB:
420 format = SND_PCM_FORMAT_S16_BE;
421 break;
422 case AUDIO_U16LSB:
423 format = SND_PCM_FORMAT_U16_LE;
424 break;
425 case AUDIO_U16MSB:
426 format = SND_PCM_FORMAT_U16_BE;
427 break;
428 default:
429 format = 0;
430 break;
431 }
432 if ( format != 0 ) {
433 status = SDL_NAME(snd_pcm_hw_params_set_format)(pcm_handle, hwparams, format);
434 }
435 if ( status < 0 ) {
436 test_format = SDL_NextAudioFormat();
437 }
438 }
439 if ( status < 0 ) {
440 SDL_SetError("Couldn't find any hardware audio formats");
441 ALSA_CloseAudio(this);
442 return(-1);
443 }
444 spec->format = test_format;
445
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 if ( (status <= 0) || (status > 2) ) {
451 SDL_SetError("Couldn't set audio channels");
452 ALSA_CloseAudio(this);
453 return(-1);
454 }
455 spec->channels = status;
456 }
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 ALSA_CloseAudio(this);
463 return(-1);
464 }
465 spec->freq = status;
466
467 /* Set the buffer size, in samples */
468 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 status = SDL_NAME(snd_pcm_hw_params)(pcm_handle, hwparams);
475 if ( status < 0 ) {
476 SDL_SetError("Couldn't set hardware audio parameters: %s", SDL_NAME(snd_strerror)(status));
477 ALSA_CloseAudio(this);
478 return(-1);
479 }
480
481 /* This is useful for debugging... */
482 /*
483 { snd_pcm_sframes_t bufsize; int fragments;
484 bufsize = SDL_NAME(snd_pcm_hw_params_get_period_size)(hwparams);
485 fragments = SDL_NAME(snd_pcm_hw_params_get_periods)(hwparams);
486
487 fprintf(stderr, "ALSA: bufsize = %ld, fragments = %d\n", bufsize, fragments);
488 }
489 */
490
491 /* Set the software parameters */
492 snd_pcm_sw_params_alloca(&swparams);
493 status = SDL_NAME(snd_pcm_sw_params_current)(pcm_handle, swparams);
494 if ( status < 0 ) {
495 SDL_SetError("Couldn't get software config: %s", SDL_NAME(snd_strerror)(status));
496 ALSA_CloseAudio(this);
497 return(-1);
498 }
499 status = SDL_NAME(snd_pcm_sw_params_set_start_threshold)(pcm_handle, swparams, 0);
500 if ( status < 0 ) {
501 SDL_SetError("Couldn't set start threshold: %s", SDL_NAME(snd_strerror)(status));
502 ALSA_CloseAudio(this);
503 return(-1);
504 }
505 status = SDL_NAME(snd_pcm_sw_params_set_avail_min)(pcm_handle, swparams, frames);
506 if ( status < 0 ) {
507 SDL_SetError("Couldn't set avail min: %s", SDL_NAME(snd_strerror)(status));
508 ALSA_CloseAudio(this);
509 return(-1);
510 }
511 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 return(-1);
516 }
517
518 /* Calculate the final parameters for this audio specification */
519 SDL_CalculateAudioSpec(spec);
520
521 /* Allocate mixing buffer */
522 mixlen = spec->size;
523 mixbuf = (Uint8 *)SDL_AllocAudioMem(mixlen);
524 if ( mixbuf == NULL ) {
525 ALSA_CloseAudio(this);
526 return(-1);
527 }
528 SDL_memset(mixbuf, spec->silence, spec->size);
529
530 /* Get the parent process id (we're the parent of the audio thread) */
531 parent = getpid();
532
533 /* Switch to blocking mode for playback */
534 SDL_NAME(snd_pcm_nonblock)(pcm_handle, 0);
535
536 /* We're ready to rock and roll. :-) */
537 return(0);
538 }
539