Browser-wide audio mirroring for TabCapture API

media/audio/audio_manager_base.h

Index: media/audio/audio_manager_base.h
diff --git a/media/audio/audio_manager_base.h b/media/audio/audio_manager_base.h
index 57b4fe44edb67707401d4b55bd4441dcda9c1dea..60c085ad1f65e437b8fd1d5e981ccfcca959b9d6 100644
--- a/media/audio/audio_manager_base.h
+++ b/media/audio/audio_manager_base.h
@@ -27,6 +27,8 @@ class Thread;
 namespace media {
 
 class AudioOutputDispatcher;
+class VirtualAudioInputStream;
+class VirtualAudioOutputStream;
 
 // AudioManagerBase provides AudioManager functions common for all platforms.
 class MEDIA_EXPORT AudioManagerBase : public AudioManager {
@@ -62,6 +64,8 @@ class MEDIA_EXPORT AudioManagerBase : public AudioManager {
   // 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();
@@ -159,6 +163,11 @@ class MEDIA_EXPORT AudioManagerBase : public AudioManager {
   // 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);
 };