First step towards moving AudioDevice from content/ to media/audio.

content/renderer/media/audio_input_device.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.
 
-// Low-latency audio capturing unit utilizing audio input stream provided
-// by browser process through IPC.
+// Low-latency audio capturing class utilizing audio input stream provided
+// by a server (browser) process by use of an IPC interface.
 //
 // Relationship of classes:
 //
 //  AudioInputController                 AudioInputDevice
 //           ^                                  ^
 //           |                                  |
 //           v                  IPC             v
-// AudioInputRendererHost  <---------> AudioInputMessageFilter
-//           ^
+// AudioInputRendererHost  <---------> media::AudioInputIPCDelegate
+//           ^                       (impl in AudioInputMessageFilter)
 //           |
 //           v
 // AudioInputDeviceManager
 //
 // Transportation of audio samples from the browser to the render process
-// is done by using shared memory in combination with a sync socket pair
-// to generate a low latency transport. The AudioInputDevice user registers
-// an AudioInputDevice::CaptureCallback at construction and will be called
-// by the AudioInputDevice with recorded audio from the underlying audio layers.
+// is done by using shared memory in combination with a SyncSocket.
+// The AudioInputDevice user registers an AudioInputDevice::CaptureCallback by
+// calling Initialize().  The callback will be called with recorded audio from
+// the underlying audio layers.
 // The session ID is used by the AudioInputRendererHost to start the device
 // referenced by this ID.
 //
 // State sequences:
 //
-//            Task [IO thread]                  IPC [IO thread]
-//
 // Sequence where session_id has not been set using SetDevice():
-// Start -> InitializeOnIOThread -----> AudioInputHostMsg_CreateStream ------->
-//     <- OnLowLatencyCreated <- AudioInputMsg_NotifyLowLatencyStreamCreated <-
-//       ---> StartOnIOThread ---------> AudioInputHostMsg_PlayStream -------->
+// ('<-' signifies callbacks, -> signifies calls made by AudioInputDevice)
+// Start -> InitializeOnIOThread -> CreateStream ->
+//       <- OnStreamCreated <-
+//       -> StartOnIOThread -> PlayStream ->
 //
 // Sequence where session_id has been set using SetDevice():
-// Start ->  InitializeOnIOThread --> AudioInputHostMsg_StartDevice --->
-//      <---- OnStarted <-------------- AudioInputMsg_NotifyDeviceStarted <----
-//       -> OnDeviceReady ------------> AudioInputHostMsg_CreateStream ------->
-//     <- OnLowLatencyCreated <- AudioInputMsg_NotifyLowLatencyStreamCreated <-
-//       ---> StartOnIOThread ---------> AudioInputHostMsg_PlayStream -------->
+// Start -> InitializeOnIOThread -> StartDevice ->
+//       <- OnDeviceReady <-
+//       -> CreateStream ->
+//       <- OnStreamCreated <-
+//       -> StartOnIOThread -> PlayStream ->
 //
 // AudioInputDevice::Capture => low latency audio transport on audio thread =>
 //                               |
-// Stop --> ShutDownOnIOThread ------>  AudioInputHostMsg_CloseStream -> Close
+// Stop --> ShutDownOnIOThread ------>  CloseStream -> Close
 //
-// This class utilizes three threads during its lifetime, namely:
+// This class depends on two threads to function:
 //
-// 1. Creating thread.
-//    Must be the main render thread. Start and Stop should be called on
-//    this thread.
-// 2. IO thread.
-//    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 CaptrureCallback and feed audio samples from
-//    the audio layer in the browser process using sync sockets and shared
-//    memory.
+// 1. An IO thread.
+//    This thread is used to asynchronously process Start/Stop etc operations
+//    that are available via the public interface.  The public methods are
+//    asynchronous and simply post a task to the IO thread to actually perform
+//    the work.
+// 2. Audio transport thread.
+//    Responsible for calling the CaptureCallback and feed audio samples from
+//    the server side audio layer using a socket and shared memory.
 //
 // Implementation notes:
-//
-// - Start() is asynchronous/non-blocking.
-// - Stop() is synchronous/blocking.
-// - SetDevice() is asynchronous/non-blocking.
 // - The user must call Stop() before deleting the class instance.
 
 #ifndef CONTENT_RENDERER_MEDIA_AUDIO_INPUT_DEVICE_H_
 #define CONTENT_RENDERER_MEDIA_AUDIO_INPUT_DEVICE_H_
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/shared_memory.h"
 #include "content/common/content_export.h"
 #include "content/renderer/media/audio_device_thread.h"
 #include "content/renderer/media/audio_input_message_filter.h"
 #include "content/renderer/media/scoped_loop_observer.h"
 #include "media/audio/audio_parameters.h"
 
 // TODO(henrika): This class is based on the AudioDevice class and it has
 // many components in common. Investigate potential for re-factoring.
 // TODO(henrika): Add support for event handling (e.g. OnStateChanged,
 // OnCaptureStopped etc.) and ensure that we can deliver these notifications
 // to any clients using this class.
 class CONTENT_EXPORT AudioInputDevice
-    : public AudioInputMessageFilter::Delegate,
+    : NON_EXPORTED_BASE(public media::AudioInputIPCDelegate),
       NON_EXPORTED_BASE(public ScopedLoopObserver),
       public base::RefCountedThreadSafe<AudioInputDevice> {
  public:
   class CONTENT_EXPORT CaptureCallback {
    public:
     virtual void Capture(const std::vector<float*>& audio_data,
                          int number_of_frames,
                          int audio_delay_milliseconds,
                          double volume) = 0;
     virtual void OnCaptureError() = 0;
    protected:
     virtual ~CaptureCallback() {}
   };
 
   class CONTENT_EXPORT CaptureEventHandler {
    public:
     // Notification to the client that the device with the specific |device_id|
     // has been started.
     // This callback is triggered as a result of StartDevice().
     virtual void OnDeviceStarted(const std::string& device_id) = 0;
 
     // Notification to the client that the device has been stopped.
     virtual void OnDeviceStopped() = 0;
 
    protected:
     virtual ~CaptureEventHandler() {}
   };
 
-  // Methods called on main render thread -------------------------------------
-  AudioInputDevice(const media::AudioParameters& params,
-                   CaptureCallback* callback,
-                   CaptureEventHandler* event_handler);
+  AudioInputDevice(media::AudioInputIPC* ipc,
+                   const scoped_refptr<base::MessageLoopProxy>& io_loop);
+
+  // Initializes the AudioInputDevice.  This method must be called before
+  // any other methods can be used.
+  void Initialize(const media::AudioParameters& params,
+                  CaptureCallback* callback,
+                  CaptureEventHandler* event_handler);
 
   // Specify the |session_id| to query which device to use. This method is
   // asynchronous/non-blocking.
   // Start() will use the second sequence if this method is called before.
   void SetDevice(int session_id);
 
   // Starts audio capturing. This method is asynchronous/non-blocking.
   // TODO(henrika): add support for notification when recording has started.
   void Start();
 
   // Stops audio capturing. This method is synchronous/blocking.
   // TODO(henrika): add support for notification when recording has stopped.
   void Stop();
 
   // Sets the capture volume scaling, with range [0.0, 1.0] inclusive.
   // Returns |true| on success.
   bool SetVolume(double volume);
 
-  // Gets the capture volume scaling, with range [0.0, 1.0] inclusive.
-  // Returns |true| on success.
-  bool GetVolume(double* volume);
-
-  double sample_rate() const {
-    return audio_parameters_.sample_rate();
-  }
-
-  int buffer_size() const {
-    return audio_parameters_.frames_per_buffer();
-  }
-
   // Sets the Automatic Gain Control state to on or off.
   // This method must be called before Start(). It will not have any effect
   // if it is called while capturing has already started.
   void SetAutomaticGainControl(bool enabled);
 
+ protected:
   // Methods called on IO thread ----------------------------------------------
-  // AudioInputMessageFilter::Delegate impl., called by AudioInputMessageFilter.
+  // media::AudioInputIPCDelegate implementation.
   virtual void OnStreamCreated(base::SharedMemoryHandle handle,
                                base::SyncSocket::Handle socket_handle,
-                               uint32 length) OVERRIDE;
+                               int length) OVERRIDE;
   virtual void OnVolume(double volume) OVERRIDE;
-  virtual void OnStateChanged(AudioStreamState state) OVERRIDE;
+  virtual void OnStateChanged(
+      media::AudioInputIPCDelegate::State state) OVERRIDE;
   virtual void OnDeviceReady(const std::string& device_id) OVERRIDE;
+  virtual void OnIPCClosed() OVERRIDE;
 
- protected:
+  friend class base::RefCountedThreadSafe<AudioInputDevice>;
   virtual ~AudioInputDevice();
 
  private:
-  friend class base::RefCountedThreadSafe<AudioInputDevice>;
-
   // Methods called on IO thread ----------------------------------------------
   // The following methods are tasks posted on the IO thread that needs to
   // be executed on that thread. They interact with AudioInputMessageFilter and
   // sends IPC messages on that thread.
   void InitializeOnIOThread();
   void SetSessionIdOnIOThread(int session_id);
   void StartOnIOThread();
   void ShutDownOnIOThread();
   void SetVolumeOnIOThread(double volume);
   void SetAutomaticGainControlOnIOThread(bool enabled);
 
-  void Send(IPC::Message* message);
-
   // MessageLoop::DestructionObserver implementation for the IO loop.
   // If the IO loop dies before we do, we shut down the audio thread from here.
   virtual void WillDestroyCurrentMessageLoop() OVERRIDE;
 
-  // Format
   media::AudioParameters audio_parameters_;
 
   CaptureCallback* callback_;
   CaptureEventHandler* event_handler_;
 
-  // The current volume scaling [0.0, 1.0] of the audio stream.
-  double volume_;
-
-  // Cached audio input message filter (lives on the main render thread).
-  scoped_refptr<AudioInputMessageFilter> filter_;
+  media::AudioInputIPC* ipc_;
 
   // Our stream ID on the message filter. Only modified on the IO thread.
-  int32 stream_id_;
+  int stream_id_;
 
   // The media session ID used to identify which input device to be started.
   // Only modified on the IO thread.
   int session_id_;
 
   // State variable used to indicate it is waiting for a OnDeviceReady()
   // callback. Only modified on the IO thread.
   bool pending_device_ready_;
 
   // Stores the Automatic Gain Control state. Default is false.
   // Only modified on the IO thread.
   bool agc_is_enabled_;
 
   // Our audio thread callback class.  See source file for details.
   class AudioThreadCallback;
 
   // In order to avoid a race between OnStreamCreated and Stop(), we use this
   // guard to control stopping and starting the audio thread.
   base::Lock audio_thread_lock_;
   AudioDeviceThread audio_thread_;
   scoped_ptr<AudioInputDevice::AudioThreadCallback> audio_callback_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(AudioInputDevice);
 };
 
 #endif  // CONTENT_RENDERER_MEDIA_AUDIO_INPUT_DEVICE_H_