Remove "high"-latency audio code path

content/browser/renderer_host/media/audio_renderer_host.h

 // Copyright (c) 2011 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.
 //
 // AudioRendererHost serves audio related requests from AudioRenderer which
 // lives inside the render process and provide access to audio hardware.
 //
 // This class is owned by BrowserRenderProcessHost, and instantiated on UI
 // thread, but all other operations and method calls happen on IO thread, so we
 // need to be extra careful about the lifetime of this object. AudioManager is a
 // singleton and created in IO thread, audio output streams are also created in
 // the IO thread, so we need to destroy them also in IO thread. After this class
 // is created, a task of OnInitialized() is posted on IO thread in which
-// singleton of AudioManager is created and.
+// singleton of AudioManager is created.
 //
 // Here's an example of a typical IPC dialog for audio:
 //
 //   Renderer                     AudioRendererHost
 //      |                               |
 //      |         CreateStream >        |
-//      |          < Created            |
+//      |     < NotifyStreamCreated     |
 //      |                               |
-//      |             Play >            |
-//      |           < Playing           |  time
+//      |          PlayStream >         |
+//      |  < NotifyStreamStateChanged   | kAudioStreamPlaying
 //      |                               |
-//      |     < RequestAudioPacket      |
-//      |      AudioPacketReady >       |
+//      |         PauseStream >         |
+//      |  < NotifyStreamStateChanged   | kAudioStreamPaused
+//      |                               |
+//      |          PlayStream >         |
+//      |  < NotifyStreamStateChanged   | kAudioStreamPlaying
 //      |             ...               |
-//      |     < RequestAudioPacket      |
-//      |      AudioPacketReady >       |
-//      |                               |
-//      |             ...               |
-//      |     < RequestAudioPacket      |
-//      |      AudioPacketReady >       |
-//      |             ...               |
-//      |           Pause >             |
-//      |          < Paused             |
-//      |            ...                |
-//      |           Start >             |
-//      |          < Started            |
-//      |             ...               |
-//      |            Close >            |
+//      |         CloseStream >         |
 //      v                               v
 
-// The above mode of operation uses relatively big buffers and has latencies
-// of 50 ms or more. There is a second mode of operation which is low latency.
-// For low latency audio, the picture above is modified by not having the
-// RequestAudioPacket and the AudioPacketReady messages, instead a SyncSocket
-// pair is used to signal buffer readiness without having to route messages
-// using the IO thread.
+// A SyncSocket pair is used to signal buffer readiness between processes.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_RENDERER_HOST_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_RENDERER_HOST_H_
 #pragma once
 
 #include <map>
 
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 29 matching lines @@
     // The audio stream ID.
     int stream_id;
 
     // Shared memory for transmission of the audio data.
     base::SharedMemory shared_memory;
 
     // The synchronous reader to be used by the controller. We have the
     // ownership of the reader.
     scoped_ptr<media::AudioOutputController::SyncReader> reader;
 
-    bool pending_buffer_request;
-
     // Set to true after we called Close() for the controller.
     bool pending_close;
   };
 
   typedef std::map<int, AudioEntry*> AudioEntryMap;
 
   // Called from UI thread from the owner of this object.
   AudioRendererHost(const content::ResourceContext* resource_context);
 
   // content::BrowserMessageFilter implementation.
   virtual void OnChannelClosing() OVERRIDE;
   virtual void OnDestruct() const OVERRIDE;
   virtual bool OnMessageReceived(const IPC::Message& message,
                                  bool* message_was_ok) OVERRIDE;
 
   // AudioOutputController::EventHandler implementations.
   virtual void OnCreated(media::AudioOutputController* controller) OVERRIDE;
   virtual void OnPlaying(media::AudioOutputController* controller) OVERRIDE;
   virtual void OnPaused(media::AudioOutputController* controller) OVERRIDE;
   virtual void OnError(media::AudioOutputController* controller,
                        int error_code) OVERRIDE;
-  virtual void OnMoreData(media::AudioOutputController* controller,
-                          AudioBuffersState buffers_state) OVERRIDE;
 
  private:
   friend class AudioRendererHostTest;
   friend class content::BrowserThread;
   friend class base::DeleteHelper<AudioRendererHost>;
   friend class MockAudioRendererHost;
   FRIEND_TEST_ALL_PREFIXES(AudioRendererHostTest, CreateMockStream);
   FRIEND_TEST_ALL_PREFIXES(AudioRendererHostTest, MockStreamDataConversation);
 
   virtual ~AudioRendererHost();
 
   // Methods called on IO thread ----------------------------------------------
 
   // Audio related IPC message handlers.
   // Creates an audio output stream with the specified format. If this call is
   // successful this object would keep an internal entry of the stream for the
   // required properties.
-  void OnCreateStream(int stream_id,
-                      const AudioParameters& params,
-                      bool low_latency);
+  void OnCreateStream(int stream_id, const AudioParameters& params);
 
   // Play the audio stream referenced by |stream_id|.
   void OnPlayStream(int stream_id);
 
   // Pause the audio stream referenced by |stream_id|.
   void OnPauseStream(int stream_id);
 
-  // Discard all audio data in  stream referenced by |stream_id|.
+  // Discard all audio data in stream referenced by |stream_id|.
   void OnFlushStream(int stream_id);
 
   // Close the audio stream referenced by |stream_id|.
   void OnCloseStream(int stream_id);
 
   // Set the volume of the audio stream referenced by |stream_id|.
   void OnSetVolume(int stream_id, double volume);
 
-  // Get the volume of the audio stream referenced by |stream_id|.
-  void OnGetVolume(int stream_id);
-
-  // Notify packet has been prepared for the audio stream.
-  void OnNotifyPacketReady(int stream_id, uint32 packet_size);
-
   // Complete the process of creating an audio stream. This will set up the
   // shared memory or shared socket in low latency mode.
   void DoCompleteCreation(media::AudioOutputController* controller);
 
   // Send a state change message to the renderer.
   void DoSendPlayingMessage(media::AudioOutputController* controller);
   void DoSendPausedMessage(media::AudioOutputController* controller);
 
-  // Request more data from the renderer. This method is used only in normal
-  // latency mode.
-  void DoRequestMoreData(media::AudioOutputController* controller,
-                         AudioBuffersState buffers_state);
-
   // Handle error coming from audio stream.
   void DoHandleError(media::AudioOutputController* controller, int error_code);
 
   // Send an error message to the renderer.
   void SendErrorMessage(int stream_id);
 
   // Delete all audio entry and all audio streams
   void DeleteEntries();
 
   // Closes the stream. The stream is then deleted in DeleteEntry() after it
@@ skipping 28 matching lines @@
   // A map of stream IDs to audio sources.
   AudioEntryMap audio_entries_;
 
   const content::ResourceContext* resource_context_;
   MediaObserver* media_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioRendererHost);
 };
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_RENDERER_HOST_H_