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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 | ||
05b75f8d | 24 | #include "common.h" |
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25 | |
26 | #if HAVE_ALSA_ASOUNDLIB_H | |
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27 | #include <alsa/asoundlib.h> |
28 | #include <pthread.h> | |
29 | ||
30 | #include "alsabg.h" | |
31 | #include "log.h" | |
32 | ||
33 | /** @brief Output handle */ | |
34 | static snd_pcm_t *pcm; | |
35 | ||
36 | /** @brief Called to get audio data */ | |
37 | static alsa_bg_supply *supplyfn; | |
38 | ||
39 | static pthread_t alsa_bg_collect_tid, alsa_bg_play_tid; | |
40 | ||
41 | /** @brief Set to shut down the background threads */ | |
42 | static int alsa_bg_shutdown = 0; | |
43 | ||
44 | /** @brief Number of channels (samples per frame) */ | |
45 | #define CHANNELS 2 | |
46 | ||
47 | /** @brief Number of bytes per samples */ | |
48 | #define BYTES_PER_SAMPLE 2 | |
49 | ||
50 | /** @brief Number of bytes per frame */ | |
51 | #define BYTES_PER_FRAME (CHANNELS * BYTES_PER_SAMPLE) | |
52 | ||
53 | /** @brief Buffer size in bytes */ | |
54 | #define BUFFER_BYTES 65536 | |
55 | ||
56 | /** @brief Buffer size in frames */ | |
57 | #define BUFFER_FRAMES (BUFFER_BYTES / BYTES_PER_FRAME) | |
58 | ||
59 | /** @brief Buffer size in samples */ | |
60 | #define BUFFER_SAMPLES (BUFFER_BYTES / BYTES_PER_SAMPLE) | |
61 | ||
62 | /** @brief Audio buffer */ | |
63 | static uint8_t alsa_bg_buffer[BUFFER_BYTES]; | |
64 | ||
65 | /** @brief First playable byte in audio buffer */ | |
66 | static unsigned alsa_bg_start; | |
67 | ||
68 | /** @brief Number of playable bytes in audio buffer */ | |
69 | static unsigned alsa_bg_count; | |
70 | ||
71 | /** @brief Current enable status */ | |
72 | static int alsa_bg_enabled; | |
73 | ||
74 | /** @brief Lock protecting audio buffer pointers */ | |
75 | static pthread_mutex_t alsa_bg_lock = PTHREAD_MUTEX_INITIALIZER; | |
76 | ||
77 | /** @brief Signaled when buffer contents changes */ | |
78 | static pthread_cond_t alsa_bg_cond = PTHREAD_COND_INITIALIZER; | |
79 | ||
80 | /** @brief Call a pthread_ function and fatal() on exit */ | |
81 | #define ep(x) do { \ | |
82 | int prc; \ | |
83 | \ | |
84 | if((prc = (x))) \ | |
85 | fatal(prc, "%s", #x); \ | |
86 | } while(0) | |
87 | ||
88 | /** @brief Data collection thread | |
89 | * | |
90 | * This thread collects audio data to play and stores it in the ring | |
91 | * buffer. | |
92 | */ | |
93 | static void *alsa_bg_collect(void attribute((unused)) *arg) { | |
94 | unsigned avail_start, avail_count; | |
95 | int count; | |
96 | ||
97 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
98 | for(;;) { | |
99 | /* If we're shutting down, quit straight away */ | |
100 | if(alsa_bg_shutdown) | |
101 | break; | |
102 | /* While we're disabled or the buffer is full, just wait */ | |
103 | if(!alsa_bg_enabled || alsa_bg_count == BUFFER_BYTES) { | |
104 | ep(pthread_cond_wait(&alsa_bg_cond, &alsa_bg_lock)); | |
105 | continue; | |
106 | } | |
107 | /* Figure out where and how big the gap we can write into is */ | |
108 | avail_start = alsa_bg_start + alsa_bg_count; | |
109 | if(avail_start < BUFFER_BYTES) | |
110 | avail_count = BUFFER_BYTES - avail_start; | |
111 | else { | |
112 | avail_start %= BUFFER_BYTES; | |
113 | avail_count = alsa_bg_start - avail_start; | |
114 | } | |
115 | assert(avail_start < BUFFER_BYTES); | |
116 | assert(avail_count <= BUFFER_BYTES); | |
117 | assert(avail_count + alsa_bg_count <= BUFFER_BYTES); | |
118 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
119 | count = supplyfn(alsa_bg_buffer + avail_start, | |
120 | avail_count / BYTES_PER_SAMPLE); | |
121 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
122 | alsa_bg_count += count * BYTES_PER_SAMPLE; | |
123 | assert(alsa_bg_start < BUFFER_BYTES); | |
124 | assert(alsa_bg_count <= BUFFER_BYTES); | |
125 | ep(pthread_cond_signal(&alsa_bg_cond)); | |
126 | } | |
127 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
128 | return 0; | |
129 | } | |
130 | ||
131 | /** @brief Playback thread | |
132 | * | |
133 | * This thread reads audio data out of the ring buffer and plays it back | |
134 | */ | |
135 | static void *alsa_bg_play(void attribute((unused)) *arg) { | |
136 | int prepared = 1, err; | |
137 | int start, nbytes, nframes, rframes; | |
138 | ||
139 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
140 | for(;;) { | |
141 | /* If we're shutting down, quit straight away */ | |
142 | if(alsa_bg_shutdown) | |
143 | break; | |
144 | /* Wait for some data to be available. (If we are marked disabled | |
145 | * we keep on playing what we've got.) */ | |
146 | if(alsa_bg_count == 0) { | |
147 | if(prepared) { | |
148 | if((err = snd_pcm_drain(pcm))) | |
149 | fatal(0, "snd_pcm_drain: %d", err); | |
150 | prepared = 0; | |
151 | } | |
152 | ep(pthread_cond_wait(&alsa_bg_cond, &alsa_bg_lock)); | |
153 | continue; | |
154 | } | |
155 | /* Calculate how much we can play */ | |
156 | start = alsa_bg_start; | |
157 | if(start + alsa_bg_count <= BUFFER_BYTES) | |
158 | nbytes = alsa_bg_count; | |
159 | else | |
160 | nbytes = BUFFER_BYTES - start; | |
161 | /* Limit how much of the buffer we play. The effect is that we return from | |
162 | * _writei earlier, and therefore free up more buffer space to read fresh | |
163 | * data into. /2 works fine, /4 is just conservative. /1 (i.e. abolishing | |
164 | * the heuristic) produces noticably noisy output. */ | |
165 | if(nbytes > BUFFER_BYTES / 4) | |
166 | nbytes = BUFFER_BYTES / 4; | |
167 | assert((unsigned)nbytes <= alsa_bg_count); | |
168 | nframes = nbytes / BYTES_PER_FRAME; | |
169 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
170 | /* Make sure the PCM is prepared */ | |
171 | if(!prepared) { | |
172 | if((err = snd_pcm_prepare(pcm))) | |
173 | fatal(0, "snd_pcm_prepare: %d", err); | |
174 | prepared = 1; | |
175 | } | |
176 | /* Play what we can */ | |
177 | rframes = snd_pcm_writei(pcm, alsa_bg_buffer + start, nframes); | |
178 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
179 | if(rframes < 0) { | |
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180 | switch(rframes) { |
181 | case -EPIPE: | |
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182 | error(0, "underrun detected"); |
183 | if((err = snd_pcm_prepare(pcm))) | |
184 | fatal(0, "snd_pcm_prepare: %d", err); | |
4dadf1a2 | 185 | break; |
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186 | default: |
187 | fatal(0, "snd_pcm_writei: %d", rframes); | |
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188 | } |
189 | } else { | |
190 | const int rbytes = rframes * BYTES_PER_FRAME; | |
191 | /*fprintf(stderr, "%5d -> %5d\n", nbytes, rbytes);*/ | |
192 | /* Update the buffer pointers */ | |
193 | alsa_bg_count -= rbytes; | |
194 | alsa_bg_start += rbytes; | |
195 | if(alsa_bg_start >= BUFFER_BYTES) | |
196 | alsa_bg_start -= BUFFER_BYTES; | |
197 | assert(alsa_bg_start < BUFFER_BYTES); | |
198 | assert(alsa_bg_count <= BUFFER_BYTES); | |
199 | /* Let the collector know we've opened up some space */ | |
200 | ep(pthread_cond_signal(&alsa_bg_cond)); | |
201 | } | |
202 | } | |
203 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
204 | return 0; | |
205 | } | |
206 | ||
207 | /** @brief Enable ALSA play */ | |
208 | void alsa_bg_enable(void) { | |
209 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
210 | alsa_bg_enabled = 1; | |
211 | ep(pthread_cond_broadcast(&alsa_bg_cond)); | |
212 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
213 | } | |
214 | ||
215 | /** @brief Disable ALSA play */ | |
216 | void alsa_bg_disable(void) { | |
217 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
218 | alsa_bg_enabled = 0; | |
219 | ep(pthread_cond_broadcast(&alsa_bg_cond)); | |
220 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
221 | } | |
222 | ||
223 | /** @brief Initialize background ALSA playback | |
224 | * @param device Target device or NULL to use default | |
225 | * @param supply Function to call to get audio data to play | |
226 | * | |
227 | * Playback is not initially enabled; see alsa_bg_enable(). When playback is | |
228 | * enabled, @p supply will be called in a background thread to request audio | |
229 | * data. It should return in a timely manner, but playback happens from a | |
230 | * further thread and delays in @p supply will not delay transfer of data to | |
231 | * the sound device (provided it doesn't actually run out). | |
232 | */ | |
233 | void alsa_bg_init(const char *device, | |
234 | alsa_bg_supply *supply) { | |
235 | snd_pcm_hw_params_t *hwparams; | |
236 | /* Only support one format for now */ | |
237 | const int sample_format = SND_PCM_FORMAT_S16_BE; | |
238 | unsigned rate = 44100; | |
239 | int err; | |
240 | ||
241 | if((err = snd_pcm_open(&pcm, | |
242 | device ? device : "default", | |
243 | SND_PCM_STREAM_PLAYBACK, | |
244 | 0))) | |
245 | fatal(0, "error from snd_pcm_open: %d", err); | |
246 | /* Set up 'hardware' parameters */ | |
247 | snd_pcm_hw_params_alloca(&hwparams); | |
248 | if((err = snd_pcm_hw_params_any(pcm, hwparams)) < 0) | |
249 | fatal(0, "error from snd_pcm_hw_params_any: %d", err); | |
250 | if((err = snd_pcm_hw_params_set_access(pcm, hwparams, | |
251 | SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) | |
252 | fatal(0, "error from snd_pcm_hw_params_set_access: %d", err); | |
253 | if((err = snd_pcm_hw_params_set_format(pcm, hwparams, | |
254 | sample_format)) < 0) | |
255 | ||
256 | fatal(0, "error from snd_pcm_hw_params_set_format (%d): %d", | |
257 | sample_format, err); | |
258 | if((err = snd_pcm_hw_params_set_rate_near(pcm, hwparams, &rate, 0)) < 0) | |
259 | fatal(0, "error from snd_pcm_hw_params_set_rate (%d): %d", | |
260 | rate, err); | |
261 | if((err = snd_pcm_hw_params_set_channels(pcm, hwparams, | |
262 | CHANNELS)) < 0) | |
263 | fatal(0, "error from snd_pcm_hw_params_set_channels (%d): %d", | |
264 | CHANNELS, err); | |
265 | if((err = snd_pcm_hw_params(pcm, hwparams)) < 0) | |
266 | fatal(0, "error calling snd_pcm_hw_params: %d", err); | |
267 | ||
268 | /* Record the audio supply function */ | |
269 | supplyfn = supply; | |
270 | ||
271 | /* Create the audio output thread */ | |
272 | alsa_bg_shutdown = 0; | |
273 | alsa_bg_enabled = 0; | |
274 | ep(pthread_create(&alsa_bg_collect_tid, 0, alsa_bg_collect, 0)); | |
275 | ep(pthread_create(&alsa_bg_play_tid, 0, alsa_bg_play, 0)); | |
276 | } | |
277 | ||
278 | void alsa_bg_close(void) { | |
279 | void *r; | |
280 | ||
281 | /* Notify background threads that we're shutting down */ | |
282 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
283 | alsa_bg_enabled = 0; | |
284 | alsa_bg_shutdown = 1; | |
285 | ep(pthread_cond_signal(&alsa_bg_cond)); | |
286 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
287 | /* Join background threads when they're done */ | |
288 | ep(pthread_join(alsa_bg_collect_tid, &r)); | |
289 | ep(pthread_join(alsa_bg_play_tid, &r)); | |
290 | /* Close audio device */ | |
291 | snd_pcm_close(pcm); | |
292 | pcm = 0; | |
293 | } | |
294 | ||
295 | #endif | |
296 | ||
297 | /* | |
298 | Local Variables: | |
299 | c-basic-offset:2 | |
300 | comment-column:40 | |
301 | fill-column:79 | |
302 | indent-tabs-mode:nil | |
303 | End: | |
304 | */ |