Avoids irregular OnMoreData callbacks on Windows using Core Audio

media/audio/win/audio_unified_win.cc

Index: media/audio/win/audio_unified_win.cc
diff --git a/media/audio/win/audio_unified_win.cc b/media/audio/win/audio_unified_win.cc
index 677f9e0260aea59c10879be3e4daef4e10a206e7..bd0426b9d14bcac6a8f186af140fa30edd3ddf2b 100644
--- a/media/audio/win/audio_unified_win.cc
+++ b/media/audio/win/audio_unified_win.cc
@@ -246,12 +246,16 @@ void WASAPIUnifiedStream::Start(AudioSourceCallback* callback) {
     return;
   }
 
-  // Reset the counter for number of rendered frames taking into account the
-  // fact that we always initialize the render side with silence.
-  UINT32 num_queued_frames = 0;
-  audio_output_client_->GetCurrentPadding(&num_queued_frames);
-  DCHECK_EQ(num_queued_frames, endpoint_render_buffer_size_frames_);
-  num_written_frames_ = num_queued_frames;
+  // Ensure that the endpoint buffer is prepared with silence.
+  UINT32 num_filled_frames = 0;
+  if (share_mode_ == AUDCLNT_SHAREMODE_SHARED) {
+    if (!FillRenderEndpointBufferWithSilence(&num_filled_frames)) {
+      DLOG(WARNING) << "Failed to prepare endpoint buffers with silence.";
+      return;
+    }
+    DCHECK_EQ(num_filled_frames, endpoint_render_buffer_size_frames_);
+  }
+  num_written_frames_ = num_filled_frames;
 
   // Start output streaming data between the endpoint buffer and the audio
   // engine.
@@ -566,4 +570,37 @@ void WASAPIUnifiedStream::StopAndJoinThread(HRESULT err) {
   HandleError(err);
 }
 
+bool WASAPIUnifiedStream::FillRenderEndpointBufferWithSilence(

[DaleCurtis, 2013/01/31 02:34:33]

Should this just be in CoreAudioUtil?

[henrika (OOO until Aug 14), 2013/01/31 14:29:38]

Good point. I will fix that.

+  UINT32* num_written_frames) {

[tommi (sloooow) - chröme, 2013/01/31 13:42:08]

indent

[henrika (OOO until Aug 14), 2013/01/31 14:29:38]

Done.

+  UINT32 num_queued_frames = 0;
+  HRESULT hr = audio_output_client_->GetCurrentPadding(&num_queued_frames);
+  if (FAILED(hr))
+    return false;
+
+  BYTE* data = NULL;
+  int num_frames_to_fill =
+      endpoint_render_buffer_size_frames_ - num_queued_frames;
+  hr = audio_render_client_->GetBuffer(num_frames_to_fill, &data);
+  if (FAILED(hr))
+    return false;
+
+  // Using the AUDCLNT_BUFFERFLAGS_SILENT flag eliminates the need to
+  // explicitly write silence data to the rendering buffer.
+  DVLOG(2) << "filling up " << num_frames_to_fill << " frames with silence";
+  hr = audio_render_client_->ReleaseBuffer(num_frames_to_fill,
+                                          AUDCLNT_BUFFERFLAGS_SILENT);

[tommi (sloooow) - chröme, 2013/01/31 13:42:08]

indent

[henrika (OOO until Aug 14), 2013/01/31 14:29:38]

Done.

+  if (FAILED(hr))
+    return false;
+
+  // Get the amount of valid, unread data that the endpoint buffer
+  // currently contains. This amount corresponds to the number of written
+  // audio frames.
+  hr = audio_output_client_->GetCurrentPadding(&num_queued_frames);
+  if (FAILED(hr))
+    return false;
+  *num_written_frames = num_queued_frames;
+
+  return SUCCEEDED(hr);

[tommi (sloooow) - chröme, 2013/01/31 13:42:08]

nit: you've already checked hr, so you can return true here.

[henrika (OOO until Aug 14), 2013/01/31 14:29:38]

I use the "hängslen och livrem" principle here ;-)

+}
+
 }  // namespace media