Browser-wide audio mirroring for TabCapture API

media/audio/audio_manager_base.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 MEDIA_AUDIO_AUDIO_MANAGER_BASE_H_
 #define MEDIA_AUDIO_AUDIO_MANAGER_BASE_H_
 
 #include <map>
 #include <string>
 #include <utility>
 
 #include "base/atomic_ref_count.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "base/synchronization/lock.h"
 #include "media/audio/audio_manager.h"
 
 #if defined(OS_WIN)
 #include "base/win/scoped_com_initializer.h"
 #endif
 
 namespace base {
 class Thread;
 }
 
 namespace media {
 
 class AudioOutputDispatcher;
+class VirtualAudioInputStream;
+class VirtualAudioOutputStream;
 
 // AudioManagerBase provides AudioManager functions common for all platforms.
 class MEDIA_EXPORT AudioManagerBase : public AudioManager {
  public:
   // Name of the generic "default" device.
   static const char kDefaultDeviceName[];
   // Unique Id of the generic "default" device.
   static const char kDefaultDeviceId[];
 
   virtual ~AudioManagerBase();
@@ skipping 15 matching lines @@
       const AudioParameters& params, const std::string& device_id) OVERRIDE;
 
   virtual AudioOutputStream* MakeAudioOutputStreamProxy(
       const AudioParameters& params) OVERRIDE;
 
   virtual bool IsRecordingInProcess() OVERRIDE;
 
   // Called internally by the audio stream when it has been closed.
   virtual void ReleaseOutputStream(AudioOutputStream* stream);
   virtual void ReleaseInputStream(AudioInputStream* stream);
+  // Used by VirtualAudioOutputStreams
+  virtual void ReleaseVirtualOutputStream(VirtualAudioOutputStream* stream);
 
   void IncreaseActiveInputStreamCount();
   void DecreaseActiveInputStreamCount();
 
   // Creates the output stream for the |AUDIO_PCM_LINEAR| format. The legacy
   // name is also from |AUDIO_PCM_LINEAR|.
   virtual AudioOutputStream* MakeLinearOutputStream(
       const AudioParameters& params) = 0;
 
   // Creates the output stream for the |AUDIO_PCM_LOW_LATENCY| format.
@@ skipping 77 matching lines @@
 
   // Thread used to interact with audio streams created by this audio manager.
   scoped_ptr<base::Thread> audio_thread_;
   mutable base::Lock audio_thread_lock_;
 
   // The message loop of the audio thread this object runs on. Used for internal
   // tasks which run on the audio thread even after Shutdown() has been started
   // and GetMessageLoop() starts returning NULL.
   scoped_refptr<base::MessageLoopProxy> message_loop_;
 
+  // Currently active virtual audio input stream. When this is set, we will
+  // create all audio output streams as virtual streams so as to redirect them
+  // to this virtual input stream for tab audio capture.
+  VirtualAudioInputStream* virtual_audio_input_stream_;

[no longer working on chromium, 2012/11/26 22:20:07]

does it mean that when tab capture is being used, no more normal audio stream
can be created?

[justinlin, 2012/11/27 22:26:12]

Yes. We want to eventually be able to do this for only streams from a specific
tab (Yuri is working on this), but right now since it's "whole-browser audio
mirroring", all output streams will be created as "virtual output streams" when
this is active.

So, we get no audio to speakers when tab mirroring is active. We've talked about
duplicating the audio, but there are performance and complexity issues with
that.

+
   DISALLOW_COPY_AND_ASSIGN(AudioManagerBase);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_MANAGER_BASE_H_