Don't start WASAPI render thread until setup completes.

media/audio/win/audio_low_latency_output_win.h

 // 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.
 
 // Implementation of AudioOutputStream for Windows using Windows Core Audio
 // WASAPI for low latency rendering.
 //
 // Overview of operation and performance:
 //
 // - An object of WASAPIAudioOutputStream is created by the AudioManager
@@ skipping 139 matching lines @@
   bool started() const { return render_thread_.get() != NULL; }
 
  private:
   // DelegateSimpleThread::Delegate implementation.
   virtual void Run() OVERRIDE;
 
   // Core part of the thread loop which controls the actual rendering.
   // Checks available amount of space in the endpoint buffer and reads
   // data from the client to fill up the buffer without causing audio
   // glitches.
-  bool RenderAudioFromSource(IAudioClock* audio_clock, UINT64 device_frequency);
+  bool RenderAudioFromSource(UINT64 device_frequency);
 
   // Called when the device will be opened in exclusive mode and use the
   // application specified format.
   // TODO(henrika): rewrite and move to CoreAudioUtil when removing flag
   // for exclusive audio mode.
   HRESULT ExclusiveModeInitialization(IAudioClient* client,
                                       HANDLE event_handle,
                                       uint32* endpoint_buffer_size);
 
   // If |render_thread_| is valid, sets |stop_render_event_| and blocks until
@@ skipping 28 matching lines @@
   float volume_;
 
   // Size in audio frames of each audio packet where an audio packet
   // is defined as the block of data which the source is expected to deliver
   // in each OnMoreData() callback.
   size_t packet_size_frames_;
 
   // Size in bytes of each audio packet.
   size_t packet_size_bytes_;
 
-  // Size in milliseconds of each audio packet.
-  float packet_size_ms_;
-
   // Length of the audio endpoint buffer.
   uint32 endpoint_buffer_size_frames_;
 
   // The target device id or an empty string for the default device.
   const std::string device_id_;
 
   // Defines the role that the system has assigned to an audio endpoint device.
   ERole device_role_;
 
   // The sharing mode for the connection.
   // Valid values are AUDCLNT_SHAREMODE_SHARED and AUDCLNT_SHAREMODE_EXCLUSIVE
   // where AUDCLNT_SHAREMODE_SHARED is the default.
   AUDCLNT_SHAREMODE share_mode_;
 
   // Counts the number of audio frames written to the endpoint buffer.
   UINT64 num_written_frames_;
 
   // Pointer to the client that will deliver audio samples to be played out.
   AudioSourceCallback* source_;
 
-  // An IMMDeviceEnumerator interface which represents a device enumerator.
-  base::win::ScopedComPtr<IMMDeviceEnumerator> device_enumerator_;
-
   // An IAudioClient interface which enables a client to create and initialize
   // an audio stream between an audio application and the audio engine.
   base::win::ScopedComPtr<IAudioClient> audio_client_;
 
   // The IAudioRenderClient interface enables a client to write output
   // data to a rendering endpoint buffer.
   base::win::ScopedComPtr<IAudioRenderClient> audio_render_client_;
 
   // The audio engine will signal this event each time a buffer becomes
   // ready to be filled by the client.
   base::win::ScopedHandle audio_samples_render_event_;
 
   // This event will be signaled when rendering shall stop.
   base::win::ScopedHandle stop_render_event_;
 
   // Container for retrieving data from AudioSourceCallback::OnMoreData().
   scoped_ptr<AudioBus> audio_bus_;
 
+  base::win::ScopedComPtr<IAudioClock> audio_clock_;
+
   DISALLOW_COPY_AND_ASSIGN(WASAPIAudioOutputStream);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_WIN_AUDIO_LOW_LATENCY_OUTPUT_WIN_H_