+ {
+ snd_pcm_t *pcm;
+ snd_pcm_hw_params_t *hwparams;
+ snd_pcm_sw_params_t *swparams;
+ /* Only support one format for now */
+ const int sample_format = SND_PCM_FORMAT_S16_BE;
+ unsigned rate = 44100;
+ const int channels = 2;
+ const int samplesize = channels * sizeof(uint16_t);
+ snd_pcm_uframes_t pcm_bufsize = MAXSAMPLES * samplesize * 3;
+ /* If we can write more than this many samples we'll get a wakeup */
+ const int avail_min = 256;
+ snd_pcm_sframes_t frames_written;
+ size_t samples_written;
+ int prepared = 1;
+ int err;
+
+ /* Open ALSA */
+ if((err = snd_pcm_open(&pcm,
+ device ? device : "default",
+ SND_PCM_STREAM_PLAYBACK,
+ SND_PCM_NONBLOCK)))
+ fatal(0, "error from snd_pcm_open: %d", err);
+ /* Set up 'hardware' parameters */
+ snd_pcm_hw_params_alloca(&hwparams);
+ if((err = snd_pcm_hw_params_any(pcm, hwparams)) < 0)
+ fatal(0, "error from snd_pcm_hw_params_any: %d", err);
+ if((err = snd_pcm_hw_params_set_access(pcm, hwparams,
+ SND_PCM_ACCESS_RW_INTERLEAVED)) < 0)
+ fatal(0, "error from snd_pcm_hw_params_set_access: %d", err);
+ if((err = snd_pcm_hw_params_set_format(pcm, hwparams,
+ sample_format)) < 0)
+ fatal(0, "error from snd_pcm_hw_params_set_format (%d): %d",
+ sample_format, err);
+ if((err = snd_pcm_hw_params_set_rate_near(pcm, hwparams, &rate, 0)) < 0)
+ fatal(0, "error from snd_pcm_hw_params_set_rate (%d): %d",
+ rate, err);
+ if((err = snd_pcm_hw_params_set_channels(pcm, hwparams,
+ channels)) < 0)
+ fatal(0, "error from snd_pcm_hw_params_set_channels (%d): %d",
+ channels, err);
+ if((err = snd_pcm_hw_params_set_buffer_size_near(pcm, hwparams,
+ &pcm_bufsize)) < 0)
+ fatal(0, "error from snd_pcm_hw_params_set_buffer_size (%d): %d",
+ MAXSAMPLES * samplesize * 3, err);
+ if((err = snd_pcm_hw_params(pcm, hwparams)) < 0)
+ fatal(0, "error calling snd_pcm_hw_params: %d", err);
+ /* Set up 'software' parameters */
+ snd_pcm_sw_params_alloca(&swparams);
+ if((err = snd_pcm_sw_params_current(pcm, swparams)) < 0)
+ fatal(0, "error calling snd_pcm_sw_params_current: %d", err);
+ if((err = snd_pcm_sw_params_set_avail_min(pcm, swparams, avail_min)) < 0)
+ fatal(0, "error calling snd_pcm_sw_params_set_avail_min %d: %d",
+ avail_min, err);
+ if((err = snd_pcm_sw_params(pcm, swparams)) < 0)
+ fatal(0, "error calling snd_pcm_sw_params: %d", err);
+
+ /* Ready to go */
+
+ pthread_mutex_lock(&lock);
+ for(;;) {
+ /* Wait for the buffer to fill up a bit */
+ while(nsamples < READAHEAD)
+ pthread_cond_wait(&cond, &lock);
+ if(!prepared) {
+ if((err = snd_pcm_prepare(pcm)))
+ fatal(0, "error calling snd_pcm_prepare: %d", err);
+ prepared = 1;
+ }
+ /* Wait until the buffer empties out */
+ while(nsamples >= MINBUFFER) {
+ /* Wait for ALSA to ask us for more data */
+ pthread_mutex_unlock(&lock);
+ snd_pcm_wait(pcm, -1);
+ pthread_mutex_lock(&lock);
+ /* ALSA wants more data */
+ if(packets && packets->timestamp + packets->nused == next_timestamp) {
+ /* Hooray, we have a packet we can play */
+ const size_t samples_available = packets->nsamples - packets->nused;
+ const size_t frames_available = samples_available / 2;
+
+ frames_written = snd_pcm_writei(pcm,
+ packets->samples_raw + packets->nused,
+ frames_available);
+ if(frames_written < 0)
+ fatal(0, "error calling snd_pcm_writei: %d", err);
+ samples_written = frames_written * 2;
+ packets->nused += samples_written;
+ next_timestamp += samples_written;
+ if(packets->nused == packets->nsamples) {
+ struct packet *f = packets;
+
+ packets = f->next;
+ nsamples -= f->nsamples;
+ free(f);
+ pthread_cond_broadcast(&cond);
+ }
+ } else {
+ /* We don't have anything to play! We'd better play some 0s. */
+ static const uint16_t zeros[1024];
+ size_t samples_available = 1024, frames_available;
+ if(packets && next_timestamp + samples_available > packets->timestamp)
+ samples_available = packets->timestamp - next_timestamp;
+ frames_available = samples_available / 2;
+ frames_written = snd_pcm_writei(pcm,
+ zeros,
+ frames_available);
+ if(frames_written < 0)
+ fatal(0, "error calling snd_pcm_writei: %d", err);
+ next_timestamp += samples_written;
+ }
+ }
+ /* We stop playing for a bit until the buffer re-fills */
+ pthread_mutex_unlock(&lock);
+ if((err = snd_pcm_drain(pcm)))
+ fatal(0, "error calling snd_pcm_drain: %d", err);
+ prepared = 0;
+ pthread_mutex_lock(&lock);
+ }
+
+ }