Bug 573924 - Ugly workaround for alsa-pulse bug that causes hangs after resuming audio from pause. r=chris.double a=blocking2.0

media/libsydneyaudio/src/sydney_audio_alsa.c

@@ -50,6 +50,10 @@ struct sa_stream {
   /* audio format info */
   unsigned int      rate;
   unsigned int      n_channels;
+
+  /* work around bug 573924 */
+  int               pulseaudio;
+  int               resumed;
 };
 
 /*
@@ -111,6 +115,8 @@ sa_stream_create_pcm(
   s->last_position = 0;
   s->rate         = rate;
   s->n_channels   = n_channels;
+  s->pulseaudio   = 0;
+  s->resumed      = 0;
 
   *_s = s;
   return SA_SUCCESS;
@@ -119,6 +125,9 @@ sa_stream_create_pcm(
 
 int
 sa_stream_open(sa_stream_t *s) {
+  snd_output_t* out;
+  char* buf;
+  size_t bufsz;
 
   if (s == NULL) {
     return SA_ERROR_NO_INIT;
@@ -157,6 +166,15 @@ sa_stream_open(sa_stream_t *s) {
     return SA_ERROR_NOT_SUPPORTED;
   }
   
+  /* ugly alsa-pulse plugin detection */
+  snd_output_buffer_open(&out);
+  snd_pcm_dump(s->output_unit, out);
+  bufsz = snd_output_buffer_string(out, &buf);
+  if (strncmp(buf, "ALSA <-> PulseAudio PCM I/O Plugin", bufsz) > 0 ) {
+    s->pulseaudio = 1;
+  }
+  snd_output_close(out);
+
   pthread_mutex_unlock(&sa_alsa_mutex);
 
   return SA_SUCCESS;
@@ -194,7 +212,7 @@ sa_stream_destroy(sa_stream_t *s) {
 
 int
 sa_stream_write(sa_stream_t *s, const void *data, size_t nbytes) {
-  snd_pcm_sframes_t frames, nframes;
+  snd_pcm_sframes_t frames, nframes, avail;
 
   if (s == NULL || s->output_unit == NULL) {
     return SA_ERROR_NO_INIT;
@@ -206,7 +224,14 @@ sa_stream_write(sa_stream_t *s, const void *data, size_t nbytes) {
   nframes = snd_pcm_bytes_to_frames(s->output_unit, nbytes);
 
   while(nframes>0) {
-    frames = snd_pcm_writei(s->output_unit, data, nframes);
+    if (s->resumed) {
+      avail = snd_pcm_avail_update(s->output_unit);
+      frames = snd_pcm_writei(s->output_unit, data, nframes > avail ? avail : nframes);
+      avail = snd_pcm_avail_update(s->output_unit);
+      s->resumed = avail != 0;
+    } else {
+      frames = snd_pcm_writei(s->output_unit, data, nframes);
+    }
     if (frames < 0) {
       int r = snd_pcm_recover(s->output_unit, frames, 1);
       if (r < 0) {
@@ -322,6 +347,10 @@ sa_stream_resume(sa_stream_t *s) {
     return SA_ERROR_NO_INIT;
   }
 
+  if (s->pulseaudio) {
+    s->resumed = 1;
+  }
+
   if (snd_pcm_pause(s->output_unit, 0) != 0)
     return SA_ERROR_NOT_SUPPORTED;
   return SA_SUCCESS;