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4dadf1a2 RK |
1 | /* |
2 | * This file is part of DisOrder. | |
3 | * Copyright (C) 2008 Richard Kettlewell | |
4 | * | |
e7eb3a27 | 5 | * This program is free software: you can redistribute it and/or modify |
4dadf1a2 | 6 | * it under the terms of the GNU General Public License as published by |
e7eb3a27 | 7 | * the Free Software Foundation, either version 3 of the License, or |
4dadf1a2 | 8 | * (at your option) any later version. |
e7eb3a27 RK |
9 | * |
10 | * This program 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 | |
13 | * GNU General Public License for more details. | |
14 | * | |
4dadf1a2 | 15 | * You should have received a copy of the GNU General Public License |
e7eb3a27 | 16 | * along with this program. If not, see <http://www.gnu.org/licenses/>. |
4dadf1a2 RK |
17 | */ |
18 | /** @file alsabg.c | |
19 | * @brief Background-thread interface to ALSA | |
4d82d579 RK |
20 | * |
21 | * This wraps ALSA with an interface which calls back to the client from a | |
22 | * thread. It's not intended for completely general use, just what DisOrder | |
23 | * needs. | |
24 | * | |
25 | * Only builds on Linux systems. | |
4dadf1a2 RK |
26 | */ |
27 | ||
05b75f8d | 28 | #include "common.h" |
4dadf1a2 RK |
29 | |
30 | #if HAVE_ALSA_ASOUNDLIB_H | |
4dadf1a2 RK |
31 | #include <alsa/asoundlib.h> |
32 | #include <pthread.h> | |
33 | ||
34 | #include "alsabg.h" | |
35 | #include "log.h" | |
36 | ||
37 | /** @brief Output handle */ | |
38 | static snd_pcm_t *pcm; | |
39 | ||
40 | /** @brief Called to get audio data */ | |
41 | static alsa_bg_supply *supplyfn; | |
42 | ||
43 | static pthread_t alsa_bg_collect_tid, alsa_bg_play_tid; | |
44 | ||
45 | /** @brief Set to shut down the background threads */ | |
46 | static int alsa_bg_shutdown = 0; | |
47 | ||
48 | /** @brief Number of channels (samples per frame) */ | |
49 | #define CHANNELS 2 | |
50 | ||
51 | /** @brief Number of bytes per samples */ | |
52 | #define BYTES_PER_SAMPLE 2 | |
53 | ||
54 | /** @brief Number of bytes per frame */ | |
55 | #define BYTES_PER_FRAME (CHANNELS * BYTES_PER_SAMPLE) | |
56 | ||
57 | /** @brief Buffer size in bytes */ | |
58 | #define BUFFER_BYTES 65536 | |
59 | ||
60 | /** @brief Buffer size in frames */ | |
61 | #define BUFFER_FRAMES (BUFFER_BYTES / BYTES_PER_FRAME) | |
62 | ||
63 | /** @brief Buffer size in samples */ | |
64 | #define BUFFER_SAMPLES (BUFFER_BYTES / BYTES_PER_SAMPLE) | |
65 | ||
66 | /** @brief Audio buffer */ | |
67 | static uint8_t alsa_bg_buffer[BUFFER_BYTES]; | |
68 | ||
69 | /** @brief First playable byte in audio buffer */ | |
70 | static unsigned alsa_bg_start; | |
71 | ||
72 | /** @brief Number of playable bytes in audio buffer */ | |
73 | static unsigned alsa_bg_count; | |
74 | ||
75 | /** @brief Current enable status */ | |
76 | static int alsa_bg_enabled; | |
77 | ||
78 | /** @brief Lock protecting audio buffer pointers */ | |
79 | static pthread_mutex_t alsa_bg_lock = PTHREAD_MUTEX_INITIALIZER; | |
80 | ||
81 | /** @brief Signaled when buffer contents changes */ | |
82 | static pthread_cond_t alsa_bg_cond = PTHREAD_COND_INITIALIZER; | |
83 | ||
84 | /** @brief Call a pthread_ function and fatal() on exit */ | |
85 | #define ep(x) do { \ | |
86 | int prc; \ | |
87 | \ | |
88 | if((prc = (x))) \ | |
89 | fatal(prc, "%s", #x); \ | |
90 | } while(0) | |
91 | ||
92 | /** @brief Data collection thread | |
93 | * | |
94 | * This thread collects audio data to play and stores it in the ring | |
95 | * buffer. | |
96 | */ | |
97 | static void *alsa_bg_collect(void attribute((unused)) *arg) { | |
98 | unsigned avail_start, avail_count; | |
99 | int count; | |
100 | ||
101 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
102 | for(;;) { | |
103 | /* If we're shutting down, quit straight away */ | |
104 | if(alsa_bg_shutdown) | |
105 | break; | |
106 | /* While we're disabled or the buffer is full, just wait */ | |
107 | if(!alsa_bg_enabled || alsa_bg_count == BUFFER_BYTES) { | |
108 | ep(pthread_cond_wait(&alsa_bg_cond, &alsa_bg_lock)); | |
109 | continue; | |
110 | } | |
111 | /* Figure out where and how big the gap we can write into is */ | |
112 | avail_start = alsa_bg_start + alsa_bg_count; | |
113 | if(avail_start < BUFFER_BYTES) | |
114 | avail_count = BUFFER_BYTES - avail_start; | |
115 | else { | |
116 | avail_start %= BUFFER_BYTES; | |
117 | avail_count = alsa_bg_start - avail_start; | |
118 | } | |
119 | assert(avail_start < BUFFER_BYTES); | |
120 | assert(avail_count <= BUFFER_BYTES); | |
121 | assert(avail_count + alsa_bg_count <= BUFFER_BYTES); | |
122 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
123 | count = supplyfn(alsa_bg_buffer + avail_start, | |
124 | avail_count / BYTES_PER_SAMPLE); | |
125 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
126 | alsa_bg_count += count * BYTES_PER_SAMPLE; | |
127 | assert(alsa_bg_start < BUFFER_BYTES); | |
128 | assert(alsa_bg_count <= BUFFER_BYTES); | |
129 | ep(pthread_cond_signal(&alsa_bg_cond)); | |
130 | } | |
131 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
132 | return 0; | |
133 | } | |
134 | ||
135 | /** @brief Playback thread | |
136 | * | |
137 | * This thread reads audio data out of the ring buffer and plays it back | |
138 | */ | |
139 | static void *alsa_bg_play(void attribute((unused)) *arg) { | |
140 | int prepared = 1, err; | |
141 | int start, nbytes, nframes, rframes; | |
142 | ||
143 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
144 | for(;;) { | |
145 | /* If we're shutting down, quit straight away */ | |
146 | if(alsa_bg_shutdown) | |
147 | break; | |
148 | /* Wait for some data to be available. (If we are marked disabled | |
149 | * we keep on playing what we've got.) */ | |
150 | if(alsa_bg_count == 0) { | |
151 | if(prepared) { | |
152 | if((err = snd_pcm_drain(pcm))) | |
153 | fatal(0, "snd_pcm_drain: %d", err); | |
154 | prepared = 0; | |
155 | } | |
156 | ep(pthread_cond_wait(&alsa_bg_cond, &alsa_bg_lock)); | |
157 | continue; | |
158 | } | |
159 | /* Calculate how much we can play */ | |
160 | start = alsa_bg_start; | |
161 | if(start + alsa_bg_count <= BUFFER_BYTES) | |
162 | nbytes = alsa_bg_count; | |
163 | else | |
164 | nbytes = BUFFER_BYTES - start; | |
165 | /* Limit how much of the buffer we play. The effect is that we return from | |
166 | * _writei earlier, and therefore free up more buffer space to read fresh | |
167 | * data into. /2 works fine, /4 is just conservative. /1 (i.e. abolishing | |
168 | * the heuristic) produces noticably noisy output. */ | |
169 | if(nbytes > BUFFER_BYTES / 4) | |
170 | nbytes = BUFFER_BYTES / 4; | |
171 | assert((unsigned)nbytes <= alsa_bg_count); | |
172 | nframes = nbytes / BYTES_PER_FRAME; | |
173 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
174 | /* Make sure the PCM is prepared */ | |
175 | if(!prepared) { | |
176 | if((err = snd_pcm_prepare(pcm))) | |
177 | fatal(0, "snd_pcm_prepare: %d", err); | |
178 | prepared = 1; | |
179 | } | |
180 | /* Play what we can */ | |
181 | rframes = snd_pcm_writei(pcm, alsa_bg_buffer + start, nframes); | |
182 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
183 | if(rframes < 0) { | |
4dadf1a2 RK |
184 | switch(rframes) { |
185 | case -EPIPE: | |
2956aeb4 RK |
186 | error(0, "underrun detected"); |
187 | if((err = snd_pcm_prepare(pcm))) | |
188 | fatal(0, "snd_pcm_prepare: %d", err); | |
4dadf1a2 | 189 | break; |
2956aeb4 RK |
190 | default: |
191 | fatal(0, "snd_pcm_writei: %d", rframes); | |
4dadf1a2 RK |
192 | } |
193 | } else { | |
194 | const int rbytes = rframes * BYTES_PER_FRAME; | |
195 | /*fprintf(stderr, "%5d -> %5d\n", nbytes, rbytes);*/ | |
196 | /* Update the buffer pointers */ | |
197 | alsa_bg_count -= rbytes; | |
198 | alsa_bg_start += rbytes; | |
199 | if(alsa_bg_start >= BUFFER_BYTES) | |
200 | alsa_bg_start -= BUFFER_BYTES; | |
201 | assert(alsa_bg_start < BUFFER_BYTES); | |
202 | assert(alsa_bg_count <= BUFFER_BYTES); | |
203 | /* Let the collector know we've opened up some space */ | |
204 | ep(pthread_cond_signal(&alsa_bg_cond)); | |
205 | } | |
206 | } | |
207 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
208 | return 0; | |
209 | } | |
210 | ||
211 | /** @brief Enable ALSA play */ | |
212 | void alsa_bg_enable(void) { | |
213 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
214 | alsa_bg_enabled = 1; | |
215 | ep(pthread_cond_broadcast(&alsa_bg_cond)); | |
216 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
217 | } | |
218 | ||
219 | /** @brief Disable ALSA play */ | |
220 | void alsa_bg_disable(void) { | |
221 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
222 | alsa_bg_enabled = 0; | |
223 | ep(pthread_cond_broadcast(&alsa_bg_cond)); | |
224 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
225 | } | |
226 | ||
227 | /** @brief Initialize background ALSA playback | |
228 | * @param device Target device or NULL to use default | |
229 | * @param supply Function to call to get audio data to play | |
230 | * | |
231 | * Playback is not initially enabled; see alsa_bg_enable(). When playback is | |
232 | * enabled, @p supply will be called in a background thread to request audio | |
233 | * data. It should return in a timely manner, but playback happens from a | |
234 | * further thread and delays in @p supply will not delay transfer of data to | |
235 | * the sound device (provided it doesn't actually run out). | |
236 | */ | |
237 | void alsa_bg_init(const char *device, | |
238 | alsa_bg_supply *supply) { | |
239 | snd_pcm_hw_params_t *hwparams; | |
240 | /* Only support one format for now */ | |
241 | const int sample_format = SND_PCM_FORMAT_S16_BE; | |
242 | unsigned rate = 44100; | |
243 | int err; | |
244 | ||
245 | if((err = snd_pcm_open(&pcm, | |
246 | device ? device : "default", | |
247 | SND_PCM_STREAM_PLAYBACK, | |
248 | 0))) | |
249 | fatal(0, "error from snd_pcm_open: %d", err); | |
250 | /* Set up 'hardware' parameters */ | |
251 | snd_pcm_hw_params_alloca(&hwparams); | |
252 | if((err = snd_pcm_hw_params_any(pcm, hwparams)) < 0) | |
253 | fatal(0, "error from snd_pcm_hw_params_any: %d", err); | |
254 | if((err = snd_pcm_hw_params_set_access(pcm, hwparams, | |
255 | SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) | |
256 | fatal(0, "error from snd_pcm_hw_params_set_access: %d", err); | |
257 | if((err = snd_pcm_hw_params_set_format(pcm, hwparams, | |
258 | sample_format)) < 0) | |
259 | ||
260 | fatal(0, "error from snd_pcm_hw_params_set_format (%d): %d", | |
261 | sample_format, err); | |
262 | if((err = snd_pcm_hw_params_set_rate_near(pcm, hwparams, &rate, 0)) < 0) | |
263 | fatal(0, "error from snd_pcm_hw_params_set_rate (%d): %d", | |
264 | rate, err); | |
265 | if((err = snd_pcm_hw_params_set_channels(pcm, hwparams, | |
266 | CHANNELS)) < 0) | |
267 | fatal(0, "error from snd_pcm_hw_params_set_channels (%d): %d", | |
268 | CHANNELS, err); | |
269 | if((err = snd_pcm_hw_params(pcm, hwparams)) < 0) | |
270 | fatal(0, "error calling snd_pcm_hw_params: %d", err); | |
271 | ||
272 | /* Record the audio supply function */ | |
273 | supplyfn = supply; | |
274 | ||
275 | /* Create the audio output thread */ | |
276 | alsa_bg_shutdown = 0; | |
277 | alsa_bg_enabled = 0; | |
278 | ep(pthread_create(&alsa_bg_collect_tid, 0, alsa_bg_collect, 0)); | |
279 | ep(pthread_create(&alsa_bg_play_tid, 0, alsa_bg_play, 0)); | |
280 | } | |
281 | ||
4d82d579 RK |
282 | /** @brief Deinitialize background ALSA playback |
283 | * | |
284 | * The opposite of alsa_bg_init(). | |
285 | */ | |
4dadf1a2 RK |
286 | void alsa_bg_close(void) { |
287 | void *r; | |
288 | ||
289 | /* Notify background threads that we're shutting down */ | |
290 | ep(pthread_mutex_lock(&alsa_bg_lock)); | |
291 | alsa_bg_enabled = 0; | |
292 | alsa_bg_shutdown = 1; | |
293 | ep(pthread_cond_signal(&alsa_bg_cond)); | |
294 | ep(pthread_mutex_unlock(&alsa_bg_lock)); | |
295 | /* Join background threads when they're done */ | |
296 | ep(pthread_join(alsa_bg_collect_tid, &r)); | |
297 | ep(pthread_join(alsa_bg_play_tid, &r)); | |
298 | /* Close audio device */ | |
299 | snd_pcm_close(pcm); | |
300 | pcm = 0; | |
301 | } | |
302 | ||
303 | #endif | |
304 | ||
305 | /* | |
306 | Local Variables: | |
307 | c-basic-offset:2 | |
308 | comment-column:40 | |
309 | fill-column:79 | |
310 | indent-tabs-mode:nil | |
311 | End: | |
312 | */ |