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1 | /* |
2 | * This file is part of DisOrder. | |
3 | * Copyright (C) 2008 Richard Kettlewell | |
4 | * | |
5 | * This program is free software; you can redistribute it and/or modify | |
6 | * it under the terms of the GNU General Public License as published by | |
7 | * the Free Software Foundation; either version 2 of the License, or | |
8 | * (at your option) any later version. | |
9 | * | |
10 | * This program is distributed in the hope that it will be useful, but | |
11 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | * General Public License for more details. | |
14 | * | |
15 | * You should have received a copy of the GNU General Public License | |
16 | * along with this program; if not, write to the Free Software | |
17 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 | |
18 | * USA | |
19 | */ | |
20 | /** @file alsabg.c | |
21 | * @brief Background-thread interface to ALSA | |
22 | */ | |
23 | ||
24 | #include <config.h> | |
25 | ||
26 | #if HAVE_ALSA_ASOUNDLIB_H | |
27 | #include "types.h" | |
28 | ||
29 | #include <alsa/asoundlib.h> | |
30 | #include <pthread.h> | |
31 | ||
32 | #include "alsabg.h" | |
33 | #include "log.h" | |
34 | ||
35 | /** @brief Output handle */ | |
36 | static snd_pcm_t *pcm; | |
37 | ||
38 | /** @brief Called to get audio data */ | |
39 | static alsa_bg_supply *supplyfn; | |
40 | ||
41 | static pthread_t alsa_bg_collect_tid, alsa_bg_play_tid; | |
42 | ||
43 | /** @brief Set to shut down the background threads */ | |
44 | static int alsa_bg_shutdown = 0; | |
45 | ||
46 | /** @brief Number of channels (samples per frame) */ | |
47 | #define CHANNELS 2 | |
48 | ||
49 | /** @brief Number of bytes per samples */ | |
50 | #define BYTES_PER_SAMPLE 2 | |
51 | ||
52 | /** @brief Number of bytes per frame */ | |
53 | #define BYTES_PER_FRAME (CHANNELS * BYTES_PER_SAMPLE) | |
54 | ||
55 | /** @brief Buffer size in bytes */ | |
56 | #define BUFFER_BYTES 65536 | |
57 | ||
58 | /** @brief Buffer size in frames */ | |
59 | #define BUFFER_FRAMES (BUFFER_BYTES / BYTES_PER_FRAME) | |
60 | ||
61 | /** @brief Buffer size in samples */ | |
62 | #define BUFFER_SAMPLES (BUFFER_BYTES / BYTES_PER_SAMPLE) | |
63 | ||
64 | /** @brief Audio buffer */ | |
65 | static uint8_t alsa_bg_buffer[BUFFER_BYTES]; | |
66 | ||
67 | /** @brief First playable byte in audio buffer */ | |
68 | static unsigned alsa_bg_start; | |
69 | ||
70 | /** @brief Number of playable bytes in audio buffer */ | |
71 | static unsigned alsa_bg_count; | |
72 | ||
73 | /** @brief Current enable status */ | |
74 | static int alsa_bg_enabled; | |
75 | ||
76 | /** @brief Lock protecting audio buffer pointers */ | |
77 | static pthread_mutex_t alsa_bg_lock = PTHREAD_MUTEX_INITIALIZER; | |
78 | ||
79 | /** @brief Signaled when buffer contents changes */ | |
80 | static pthread_cond_t alsa_bg_cond = PTHREAD_COND_INITIALIZER; | |
81 | ||
82 | /** @brief Call a pthread_ function and fatal() on exit */ | |
83 | #define ep(x) do { \ | |
84 | int prc; \ | |
85 | \ | |
86 | if((prc = (x))) \ | |
87 | fatal(prc, "%s", #x); \ | |
88 | } while(0) | |
89 | ||
90 | /** @brief Data collection thread | |
91 | * | |
92 | * This thread collects audio data to play and stores it in the ring | |
93 | * buffer. | |
94 | */ | |
95 | static void *alsa_bg_collect(void attribute((unused)) *arg) { | |
96 | unsigned avail_start, avail_count; | |
97 | int count; | |
98 | ||
99 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
100 | for(;;) { | |
101 | /* If we're shutting down, quit straight away */ | |
102 | if(alsa_bg_shutdown) | |
103 | break; | |
104 | /* While we're disabled or the buffer is full, just wait */ | |
105 | if(!alsa_bg_enabled || alsa_bg_count == BUFFER_BYTES) { | |
106 | ep(pthread_cond_wait(&alsa_bg_cond, &alsa_bg_lock)); | |
107 | continue; | |
108 | } | |
109 | /* Figure out where and how big the gap we can write into is */ | |
110 | avail_start = alsa_bg_start + alsa_bg_count; | |
111 | if(avail_start < BUFFER_BYTES) | |
112 | avail_count = BUFFER_BYTES - avail_start; | |
113 | else { | |
114 | avail_start %= BUFFER_BYTES; | |
115 | avail_count = alsa_bg_start - avail_start; | |
116 | } | |
117 | assert(avail_start < BUFFER_BYTES); | |
118 | assert(avail_count <= BUFFER_BYTES); | |
119 | assert(avail_count + alsa_bg_count <= BUFFER_BYTES); | |
120 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
121 | count = supplyfn(alsa_bg_buffer + avail_start, | |
122 | avail_count / BYTES_PER_SAMPLE); | |
123 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
124 | alsa_bg_count += count * BYTES_PER_SAMPLE; | |
125 | assert(alsa_bg_start < BUFFER_BYTES); | |
126 | assert(alsa_bg_count <= BUFFER_BYTES); | |
127 | ep(pthread_cond_signal(&alsa_bg_cond)); | |
128 | } | |
129 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
130 | return 0; | |
131 | } | |
132 | ||
133 | /** @brief Playback thread | |
134 | * | |
135 | * This thread reads audio data out of the ring buffer and plays it back | |
136 | */ | |
137 | static void *alsa_bg_play(void attribute((unused)) *arg) { | |
138 | int prepared = 1, err; | |
139 | int start, nbytes, nframes, rframes; | |
140 | ||
141 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
142 | for(;;) { | |
143 | /* If we're shutting down, quit straight away */ | |
144 | if(alsa_bg_shutdown) | |
145 | break; | |
146 | /* Wait for some data to be available. (If we are marked disabled | |
147 | * we keep on playing what we've got.) */ | |
148 | if(alsa_bg_count == 0) { | |
149 | if(prepared) { | |
150 | if((err = snd_pcm_drain(pcm))) | |
151 | fatal(0, "snd_pcm_drain: %d", err); | |
152 | prepared = 0; | |
153 | } | |
154 | ep(pthread_cond_wait(&alsa_bg_cond, &alsa_bg_lock)); | |
155 | continue; | |
156 | } | |
157 | /* Calculate how much we can play */ | |
158 | start = alsa_bg_start; | |
159 | if(start + alsa_bg_count <= BUFFER_BYTES) | |
160 | nbytes = alsa_bg_count; | |
161 | else | |
162 | nbytes = BUFFER_BYTES - start; | |
163 | /* Limit how much of the buffer we play. The effect is that we return from | |
164 | * _writei earlier, and therefore free up more buffer space to read fresh | |
165 | * data into. /2 works fine, /4 is just conservative. /1 (i.e. abolishing | |
166 | * the heuristic) produces noticably noisy output. */ | |
167 | if(nbytes > BUFFER_BYTES / 4) | |
168 | nbytes = BUFFER_BYTES / 4; | |
169 | assert((unsigned)nbytes <= alsa_bg_count); | |
170 | nframes = nbytes / BYTES_PER_FRAME; | |
171 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
172 | /* Make sure the PCM is prepared */ | |
173 | if(!prepared) { | |
174 | if((err = snd_pcm_prepare(pcm))) | |
175 | fatal(0, "snd_pcm_prepare: %d", err); | |
176 | prepared = 1; | |
177 | } | |
178 | /* Play what we can */ | |
179 | rframes = snd_pcm_writei(pcm, alsa_bg_buffer + start, nframes); | |
180 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
181 | if(rframes < 0) { | |
4dadf1a2 RK |
182 | switch(rframes) { |
183 | case -EPIPE: | |
2956aeb4 RK |
184 | error(0, "underrun detected"); |
185 | if((err = snd_pcm_prepare(pcm))) | |
186 | fatal(0, "snd_pcm_prepare: %d", err); | |
4dadf1a2 | 187 | break; |
2956aeb4 RK |
188 | default: |
189 | fatal(0, "snd_pcm_writei: %d", rframes); | |
4dadf1a2 RK |
190 | } |
191 | } else { | |
192 | const int rbytes = rframes * BYTES_PER_FRAME; | |
193 | /*fprintf(stderr, "%5d -> %5d\n", nbytes, rbytes);*/ | |
194 | /* Update the buffer pointers */ | |
195 | alsa_bg_count -= rbytes; | |
196 | alsa_bg_start += rbytes; | |
197 | if(alsa_bg_start >= BUFFER_BYTES) | |
198 | alsa_bg_start -= BUFFER_BYTES; | |
199 | assert(alsa_bg_start < BUFFER_BYTES); | |
200 | assert(alsa_bg_count <= BUFFER_BYTES); | |
201 | /* Let the collector know we've opened up some space */ | |
202 | ep(pthread_cond_signal(&alsa_bg_cond)); | |
203 | } | |
204 | } | |
205 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
206 | return 0; | |
207 | } | |
208 | ||
209 | /** @brief Enable ALSA play */ | |
210 | void alsa_bg_enable(void) { | |
211 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
212 | alsa_bg_enabled = 1; | |
213 | ep(pthread_cond_broadcast(&alsa_bg_cond)); | |
214 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
215 | } | |
216 | ||
217 | /** @brief Disable ALSA play */ | |
218 | void alsa_bg_disable(void) { | |
219 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
220 | alsa_bg_enabled = 0; | |
221 | ep(pthread_cond_broadcast(&alsa_bg_cond)); | |
222 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
223 | } | |
224 | ||
225 | /** @brief Initialize background ALSA playback | |
226 | * @param device Target device or NULL to use default | |
227 | * @param supply Function to call to get audio data to play | |
228 | * | |
229 | * Playback is not initially enabled; see alsa_bg_enable(). When playback is | |
230 | * enabled, @p supply will be called in a background thread to request audio | |
231 | * data. It should return in a timely manner, but playback happens from a | |
232 | * further thread and delays in @p supply will not delay transfer of data to | |
233 | * the sound device (provided it doesn't actually run out). | |
234 | */ | |
235 | void alsa_bg_init(const char *device, | |
236 | alsa_bg_supply *supply) { | |
237 | snd_pcm_hw_params_t *hwparams; | |
238 | /* Only support one format for now */ | |
239 | const int sample_format = SND_PCM_FORMAT_S16_BE; | |
240 | unsigned rate = 44100; | |
241 | int err; | |
242 | ||
243 | if((err = snd_pcm_open(&pcm, | |
244 | device ? device : "default", | |
245 | SND_PCM_STREAM_PLAYBACK, | |
246 | 0))) | |
247 | fatal(0, "error from snd_pcm_open: %d", err); | |
248 | /* Set up 'hardware' parameters */ | |
249 | snd_pcm_hw_params_alloca(&hwparams); | |
250 | if((err = snd_pcm_hw_params_any(pcm, hwparams)) < 0) | |
251 | fatal(0, "error from snd_pcm_hw_params_any: %d", err); | |
252 | if((err = snd_pcm_hw_params_set_access(pcm, hwparams, | |
253 | SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) | |
254 | fatal(0, "error from snd_pcm_hw_params_set_access: %d", err); | |
255 | if((err = snd_pcm_hw_params_set_format(pcm, hwparams, | |
256 | sample_format)) < 0) | |
257 | ||
258 | fatal(0, "error from snd_pcm_hw_params_set_format (%d): %d", | |
259 | sample_format, err); | |
260 | if((err = snd_pcm_hw_params_set_rate_near(pcm, hwparams, &rate, 0)) < 0) | |
261 | fatal(0, "error from snd_pcm_hw_params_set_rate (%d): %d", | |
262 | rate, err); | |
263 | if((err = snd_pcm_hw_params_set_channels(pcm, hwparams, | |
264 | CHANNELS)) < 0) | |
265 | fatal(0, "error from snd_pcm_hw_params_set_channels (%d): %d", | |
266 | CHANNELS, err); | |
267 | if((err = snd_pcm_hw_params(pcm, hwparams)) < 0) | |
268 | fatal(0, "error calling snd_pcm_hw_params: %d", err); | |
269 | ||
270 | /* Record the audio supply function */ | |
271 | supplyfn = supply; | |
272 | ||
273 | /* Create the audio output thread */ | |
274 | alsa_bg_shutdown = 0; | |
275 | alsa_bg_enabled = 0; | |
276 | ep(pthread_create(&alsa_bg_collect_tid, 0, alsa_bg_collect, 0)); | |
277 | ep(pthread_create(&alsa_bg_play_tid, 0, alsa_bg_play, 0)); | |
278 | } | |
279 | ||
280 | void alsa_bg_close(void) { | |
281 | void *r; | |
282 | ||
283 | /* Notify background threads that we're shutting down */ | |
284 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
285 | alsa_bg_enabled = 0; | |
286 | alsa_bg_shutdown = 1; | |
287 | ep(pthread_cond_signal(&alsa_bg_cond)); | |
288 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
289 | /* Join background threads when they're done */ | |
290 | ep(pthread_join(alsa_bg_collect_tid, &r)); | |
291 | ep(pthread_join(alsa_bg_play_tid, &r)); | |
292 | /* Close audio device */ | |
293 | snd_pcm_close(pcm); | |
294 | pcm = 0; | |
295 | } | |
296 | ||
297 | #endif | |
298 | ||
299 | /* | |
300 | Local Variables: | |
301 | c-basic-offset:2 | |
302 | comment-column:40 | |
303 | fill-column:79 | |
304 | indent-tabs-mode:nil | |
305 | End: | |
306 | */ |