Simplify AudioRendererImpl by using AudioDevice.

content/renderer/media/audio_device.h

Index: content/renderer/media/audio_device.h
===================================================================
--- content/renderer/media/audio_device.h	(revision 108907)
+++ content/renderer/media/audio_device.h	(working copy)
@@ -25,21 +25,23 @@
 //
 // Start -> InitializeOnIOThread ------> AudioHostMsg_CreateStream -------->
 //       <- OnLowLatencyCreated <- AudioMsg_NotifyLowLatencyStreamCreated <-
-//       ---> StartOnIOThread -----------> AudioHostMsg_PlayStream -------->
+//       ---> PlayOnIOThread -----------> AudioHostMsg_PlayStream -------->
 //
 // AudioDevice::Render => audio transport on audio thread with low latency =>
 //                               |
 // Stop --> ShutDownOnIOThread -------->  AudioHostMsg_CloseStream -> Close
 //
-// This class utilizes three threads during its lifetime, namely:
+// This class utilizes several threads during its lifetime, namely:
 // 1. Creating thread.
-//    Must be the main render thread. Start and Stop should be called on
-//    this thread.
-// 2. IO thread.
+//    Must be the main render thread.
+// 2. Control thread (may be the main render thread or another thread).
+//    The methods: Start(), Stop(), Play(), Pause(), SetVolume()
+//    Must be called on the same thread.
+// 2. IO thread (internal implementation detail - not exposed to public API)

[henrika (OOO until Aug 14), 2011/11/10 11:50:24]

You still have "two 2.:s". Should be 3.

 //    The thread within which this class receives all the IPC messages and
 //    IPC communications can only happen in this thread.
 // 3. Audio transport thread.
-//    Responsible for calling the RenderCallback and feed audio samples to
+//    Responsible for calling the RenderCallback and feeding audio samples to
 //    the audio layer in the browser process using sync sockets and shared
 //    memory.
 //
@@ -60,9 +62,8 @@
 #include "base/shared_memory.h"
 #include "base/threading/simple_thread.h"
 #include "content/renderer/media/audio_message_filter.h"
+#include "media/audio/audio_parameters.h"
 
-struct AudioParameters;
-
 class AudioDevice
     : public AudioMessageFilter::Delegate,
       public base::DelegateSimpleThread::Delegate,
@@ -78,18 +79,39 @@
   };
 
   // Methods called on main render thread -------------------------------------
+
+  // Minimal constructor where Initialize() must later be called.
+  explicit AudioDevice();
+
   AudioDevice(size_t buffer_size,
               int channels,
               double sample_rate,
               RenderCallback* callback);
   virtual ~AudioDevice();
 
+  void Initialize(size_t buffer_size,
+                  int channels,
+                  double sample_rate,
+                  AudioParameters::Format latency_format,
+                  RenderCallback* callback);
+  bool IsInitialized();
+
   // Starts audio playback.
   void Start();
 
   // Stops audio playback. Returns |true| on success.
   bool Stop();
 
+  // Resumes playback if currently paused.
+  void Play();
+
+  // Pauses playback.
+  // If |flush| is true then any pending audio which is in the pipeline
+  // (has not yet reached the hardware) will be discarded.  In this case,
+  // When Play() is later called, no previous pending audio will be
+  // rendered.
+  void Pause(bool flush);
+
   // Sets the playback volume, with range [0.0, 1.0] inclusive.
   // Returns |true| on success.
   bool SetVolume(double volume);
@@ -119,7 +141,8 @@
   // be executed on that thread. They interact with AudioMessageFilter and
   // sends IPC messages on that thread.
   void InitializeOnIOThread(const AudioParameters& params);
-  void StartOnIOThread();
+  void PlayOnIOThread();
+  void PauseOnIOThread(bool flush);
   void ShutDownOnIOThread(base::WaitableEvent* completion);
   void SetVolumeOnIOThread(double volume);
 
@@ -138,6 +161,7 @@
   int channels_;
   int bits_per_sample_;
   double sample_rate_;
+  AudioParameters::Format latency_format_;
 
   RenderCallback* callback_;
 
@@ -170,8 +194,6 @@
   // of sync sockets and shared memory to provide lowest possible latency.
   scoped_ptr<base::SharedMemory> shared_memory_;
   scoped_ptr<base::SyncSocket> socket_;
-
-  DISALLOW_IMPLICIT_CONSTRUCTORS(AudioDevice);
 };
 
 #endif  // CONTENT_RENDERER_MEDIA_AUDIO_DEVICE_H_