Tab Audio Capture: Browser-side connect/disconnect functionality.

media/audio/audio_io.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_IO_H_
 #define MEDIA_AUDIO_AUDIO_IO_H_
 
 #include "base/basictypes.h"
 #include "media/audio/audio_buffers_state.h"
 #include "media/base/audio_bus.h"
@@ skipping 31 matching lines @@
 // Because we support more audio streams than physically available channels
 // a given AudioOutputStream might or might not talk directly to hardware.
 // An audio stream allocates several buffers for audio data and calls
 // AudioSourceCallback::OnMoreData() periodically to fill these buffers,
 // as the data is written to the audio device. Size of each packet is determined
 // by |samples_per_packet| specified in AudioParameters  when the stream is
 // created.
 
 namespace media {
 
+class AudioParameters;
+
 class MEDIA_EXPORT AudioOutputStream {
  public:
   // Audio sources must implement AudioSourceCallback. This interface will be
   // called in a random thread which very likely is a high priority thread. Do
   // not rely on using this thread TLS or make calls that alter the thread
   // itself such as creating Windows or initializing COM.
   class MEDIA_EXPORT AudioSourceCallback {
    public:
     // Provide more data by fully filling |dest|.  The source will return
     // the number of frames it filled.  |buffers_state| contains current state
@@ skipping 15 matching lines @@
     // Deprecated.  DO NOT USE.  Waits until data becomes available.  Used only
     // by Windows' WaveOut clients which may be extremely laggy.  Will yield the
     // current thread until the renderer client has written its audio data or
     // 1.5 seconds have elapsed.
     virtual void WaitTillDataReady() {}
 
    protected:
     virtual ~AudioSourceCallback() {}
   };
 
+  // Audio sources may optionally implement AudioSourceDiverter to temporarily
+  // divert audio data to an alternate AudioOutputStream.  This allows the
+  // audio data to be plumbed to an alternate consumer; for example, a loopback
+  // mechanism for audio mirroring.
+  class MEDIA_EXPORT AudioSourceDiverter {

[DaleCurtis, 2013/01/08 19:23:33]

Does this need to be nested with AudioOutputStream?

[miu, 2013/01/09 02:19:41]

Done.  Moved to: base/audio/audio_source_diverter.h

+   public:
+    // Returns the audio parameters of the divertable audio data.
+    virtual const AudioParameters& GetAudioParameters() = 0;
+
+    // Start providing audio data to the given |to_stream|, which is in an
+    // unopened state.  |to_stream| remains under the control of the
+    // AudioSourceDiverter.
+    virtual void StartDiverting(AudioOutputStream* to_stream) = 0;
+
+    // Stops diverting audio data to the stream.  The AudioSourceDiverter is
+    // responsible for making sure the stream is closed, perhaps asynchronously.
+    virtual void StopDiverting() = 0;
+
+   protected:
+    virtual ~AudioSourceDiverter() {}
+  };
+
   virtual ~AudioOutputStream() {}
 
   // Open the stream. false is returned if the stream cannot be opened.  Open()
   // must always be followed by a call to Close() even if Open() fails.
   virtual bool Open() = 0;
 
   // Starts playing audio and generating AudioSourceCallback::OnMoreData().
   // Since implementor of AudioOutputStream may have internal buffers, right
   // after calling this method initial buffers are fetched.
   //
@@ skipping 74 matching lines @@
   // Sets the Automatic Gain Control (AGC) state.
   virtual void SetAutomaticGainControl(bool enabled) = 0;
 
   // Returns the Automatic Gain Control (AGC) state.
   virtual bool GetAutomaticGainControl() = 0;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_IO_H_