Always wait for DataReady() on Windows WaveOut.

media/audio/win/waveout_output_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/audio/win/waveout_output_win.h"
 
 #include <windows.h>
 #include <mmsystem.h>
 #pragma comment(lib, "winmm.lib")
 
@@ skipping 324 matching lines @@
   if (callback_)
     callback_->OnError(this, error);
 }
 
 void PCMWaveOutAudioOutputStream::QueueNextPacket(WAVEHDR *buffer) {
   DCHECK_EQ(channels_, format_.Format.nChannels);
   // Call the source which will fill our buffer with pleasant sounds and
   // return to us how many bytes were used.
   // TODO(fbarchard): Handle used 0 by queueing more.
 
+  // HACK: Yield if Read() is called too often.  On older platforms which are
+  // still using the WaveOut back end, we run into synchronization issues where

[scherkus (not reviewing), 2012/11/21 21:37:57]

s/back end/backend/

[DaleCurtis, 2012/11/21 22:42:10]

Done.

+  // the renderer has not finished filling the shared memory when Read() is
+  // called.  Reading too early will lead to clicks and pops.  See issues:
+  // http://crbug.com/161307 and http://crbug.com/61022
+  callback_->WaitTillDataReady();

[DaleCurtis, 2012/11/21 19:31:07]

I'm digging through the WaveOut docs to see if we can just do the equivalent of
"return 0" instead of waiting.

+
   // TODO(sergeyu): Specify correct hardware delay for AudioBuffersState.
   int frames_filled = callback_->OnMoreData(
       audio_bus_.get(), AudioBuffersState(pending_bytes_, 0));
   uint32 used = frames_filled * audio_bus_->channels() *
       format_.Format.wBitsPerSample / 8;
 
   if (used <= buffer_size_) {
     // Note: If this ever changes to output raw float the data must be clipped
     // and sanitized since it may come from an untrusted source such as NaCl.
     audio_bus_->ToInterleaved(
@@ skipping 52 matching lines @@
                                        buffer,
                                        sizeof(WAVEHDR));
       if (result != MMSYSERR_NOERROR)
         stream->HandleError(result);
       stream->pending_bytes_ += buffer->dwBufferLength;
     }
   }
 }
 
 }  // namespace media