Use a separate thread for audio capturing and encoding.

remoting/host/audio_scheduler.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.
 
 #ifndef REMOTING_HOST_AUDIO_SCHEDULER_H_
 #define REMOTING_HOST_AUDIO_SCHEDULER_H_
 
 #include "base/callback_forward.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/time.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 }  // namespace base
 
 namespace remoting {
 
 namespace protocol {
 class AudioStub;
 }  // namespace protocol
 
 class AudioCapturer;
 class AudioEncoder;
 class AudioPacket;
 
-// A class for controlling AudioCapturer and forwarding audio packets to the
-// client.
-//
-// THREADING
-//
-// This class works on two threads: the capture and network threads.
-// Any encoding that is done on the audio samples will be done on the capture
-// thread.
-//
-// AudioScheduler is responsible for:
-// 1. managing the AudioCapturer.
-// 2. sending packets of audio samples over the network to the client.
+// AudioScheduler is responsible for fetching audio data from the AudioCapturer
+// and encoding it before passing it to the AudioStub for delivery to the
+// client. Audio is captured and encoded on the audio thread and then passed to
+// AudioStub on the network thread.
 class AudioScheduler : public base::RefCountedThreadSafe<AudioScheduler> {
  public:
-  // Construct an AudioScheduler. TaskRunners are used for message passing
-  // among the capturer and network threads. The caller is responsible for
-  // ensuring that the |audio_capturer| and |audio_stub| outlive the
-  // AudioScheduler.
+  // Audio capture and encoding tasks are dispatched via the
+  // |audio_task_runner|. |audio_stub| tasks are dispatched via the
+  // |network_task_runner|. The caller must ensure that the |audio_capturer| and
+  // |audio_stub| exist until the scheduler is stopped using Stop() method.
   AudioScheduler(
-      scoped_refptr<base::SingleThreadTaskRunner> capture_task_runner,
+      scoped_refptr<base::SingleThreadTaskRunner> audio_task_runner,
       scoped_refptr<base::SingleThreadTaskRunner> network_task_runner,
       AudioCapturer* audio_capturer,
       scoped_ptr<AudioEncoder> audio_encoder,
       protocol::AudioStub* audio_stub);
 
   // Stop the recording session.
   void Stop(const base::Closure& done_task);
 
   // Called when a client disconnects.
   void OnClientDisconnected();
 
  private:
   friend class base::RefCountedThreadSafe<AudioScheduler>;
   virtual ~AudioScheduler();
 
   void NotifyAudioPacketCaptured(scoped_ptr<AudioPacket> packet);
 
   void DoStart();
 
   // Sends an audio packet to the client.
   void DoSendAudioPacket(scoped_ptr<AudioPacket> packet);
 
   // Signal network thread to cease activities.
   void DoStopOnNetworkThread(const base::Closure& done_task);
 
   // Called when an AudioPacket has been delivered to the client.
   void OnCaptureCallbackNotified();
 
-  scoped_refptr<base::SingleThreadTaskRunner> capture_task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> audio_task_runner_;
   scoped_refptr<base::SingleThreadTaskRunner> network_task_runner_;
 
   AudioCapturer* audio_capturer_;
 
   scoped_ptr<AudioEncoder> audio_encoder_;
 
   protocol::AudioStub* audio_stub_;
 
   bool network_stopped_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioScheduler);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_HOST_AUDIO_SCHEDULER_H_