Fix audio mirroring glitching on platforms with small buffer sizes by blocking...

Fix audio mirroring glitching on platforms with small buffer sizes by blocking while waiting for more data in VAOS::ProvideInput.

BUG=168006
TEST=Tested using --force-audio-mirroring that audio is no longer garbled on mac


Review URL: https://chromiumcodereview.appspot.com/12079086

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@180043 0039d316-1c4b-4281-b951-d872f2087c98

media/audio/audio_output_controller.cc

@@ -282,7 +282,6 @@ int AudioOutputController::OnMoreIOData(AudioBus* source,
 }
 
 void AudioOutputController::WaitTillDataReady() {
-#if defined(OS_WIN) || defined(OS_MACOSX)
   base::Time start = base::Time::Now();
   // Wait for up to 1.5 seconds for DataReady().  1.5 seconds was chosen because
   // it's larger than the playback time of the WaveOut buffer size using the
@@ -293,10 +292,6 @@ void AudioOutputController::WaitTillDataReady() {
          ((base::Time::Now() - start) < max_wait)) {
     base::PlatformThread::YieldCurrentThread();
   }
-#else
-  // WaitTillDataReady() is deprecated and should not be used.
-  CHECK(false);
-#endif
 }
 
 void AudioOutputController::OnError(AudioOutputStream* stream, int code) {

media/audio/audio_output_controller.h

@@ -141,6 +141,8 @@ class MEDIA_EXPORT AudioOutputController
                            AudioBus* dest,
                            AudioBuffersState buffers_state) OVERRIDE;
   virtual void OnError(AudioOutputStream* stream, int code) OVERRIDE;
+  // Deprecated: Currently only used for starting audio playback and for audio
+  // mirroring.
   virtual void WaitTillDataReady() OVERRIDE;
 
   // AudioDeviceListener implementation.  When called AudioOutputController will

media/audio/virtual_audio_output_stream.cc

@@ -74,7 +74,11 @@ double VirtualAudioOutputStream::ProvideInput(AudioBus* audio_bus,
   DCHECK(message_loop_->BelongsToCurrentThread());
   DCHECK(callback_);
 
-  int frames = callback_->OnMoreData(audio_bus, AudioBuffersState());
+  // A VirtualAudioInputStream with a larger buffer size may be calling this
+  // multiple times without waiting, so we need to block and ensure the data is
+  // ready to prevent glitching.
+  callback_->WaitTillDataReady();
+  const int frames = callback_->OnMoreData(audio_bus, AudioBuffersState());
   if (frames < audio_bus->frames())
     audio_bus->ZeroFramesPartial(frames, audio_bus->frames() - frames);