Fix Linux audio playback for short files

media/audio/linux/alsa_output.cc

Index: media/audio/linux/alsa_output.cc
diff --git a/media/audio/linux/alsa_output.cc b/media/audio/linux/alsa_output.cc
index d8e502cf7699b60b49c794be0faa2c289f8b0408..f933c35ad4782356bbc16289c5bd627c74112557 100644
--- a/media/audio/linux/alsa_output.cc
+++ b/media/audio/linux/alsa_output.cc
@@ -395,6 +395,10 @@ void AlsaPcmOutputStream::StartTask() {
     return;
   }
 
+  // Before starting, the buffer might have audio from previous user of this
+  // device.
+  buffer_->Clear();

[Sergey Ulanov, 2011/03/31 22:04:46]

Does this mean we cut the sound that was playing before?

[davejcool, 2011/04/09 03:10:43]

By this time, the previous stream's usage of this device has already been
stopped.  So if there's something left in the buffer, it's from the previous
stream being stopped with audio still in the buffer.  Without this clear, often
the start or end of a sound gets cut off.  

+
   // When starting again, drop all packets in the device and prepare it again
   // incase we are restarting from a pause state and need to flush old data.
   int error = wrapper_->PcmDrop(playback_handle_);
@@ -579,6 +583,13 @@ void AlsaPcmOutputStream::WritePacket() {
       // Seek forward in the buffer after we've written some data to ALSA.
       buffer_->Seek(frames_written * bytes_per_output_frame_);
     }
+  } else {
+    // If nothing left to write and playback hasn't started yet, start it now.
+    // This ensures that shorter sounds will still play.
+    if ((wrapper_->PcmState(playback_handle_) == SND_PCM_STATE_PREPARED) &&
+        GetCurrentDelay()) {

[scherkus (not reviewing), 2011/03/31 22:08:10]

GetCurrentDelay() > 0 ?

[davejcool, 2011/04/09 03:10:43]

Yes, >0 is better, thanks!

+      wrapper_->PcmStart(playback_handle_);
+    }
   }
 }