Surround Sound handling by folding 5 channels down to stereo.

media/audio/win/waveout_output_win.h

 // Copyright (c) 2006-2008 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.
 
 #ifndef MEDIA_AUDIO_WIN_WAVEOUT_OUTPUT_WIN_H_
 #define MEDIA_AUDIO_WIN_WAVEOUT_OUTPUT_WIN_H_
 
 #include <windows.h>
 #include <mmsystem.h>
 
@@ skipping 68 matching lines @@
 
   // We use the callback mostly to periodically request more audio data.
   AudioSourceCallback* callback_;
 
   // The size in bytes of each audio buffer, we usually have two of these.
   size_t buffer_size_;
 
   // Volume level from 0 to 1.
   float volume_;
 
+  // Channels from 0 to 6.
+  int channels_;
+
   // The id assigned by the operating system to the selected wave output
   // hardware device. Usually this is just -1 which means 'default device'.
   UINT device_id_;
 
   // Windows native structure to encode the format parameters.
   WAVEFORMATEX format_;
 
   // Handle to the instance of the wave device.
   HWAVEOUT waveout_;
 
   // Pointer to the first allocated audio buffer. This object owns it.
   WAVEHDR*  buffer_;
 
   // An event that is signaled when the callback thread is ready to stop.
   ScopedHandle stopped_event_;
 
   DISALLOW_COPY_AND_ASSIGN(PCMWaveOutAudioOutputStream);
 };
 
 #endif  // MEDIA_AUDIO_WIN_WAVEOUT_OUTPUT_WIN_H_