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+// Copyright (c) 2013 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.
+//
+// AudioMirroringManager is a singleton object that maintains a set of active
+// audio mirroring destinations and auto-connects/disconnects audio streams
+// to/from those destinations.  It is meant to be used exclusively on the IO
+// BrowserThread.
+//
+// How it works:
+//
+//   1. AudioRendererHost gets a CreateStream message from the render process
+//      and, among other things, creates an AudioOutputController to control the
+//      audio data flow between the render and browser processes.
+//   2. At some point, AudioRendererHost receives an "associate with render
+//      view" message.  Among other actions, it registers the
+//      AudioOutputController with AudioMirroringManager (as a Diverter).
+//   3. A user request to mirror all the audio for a single RenderView is made.
+//      A MirroringDestination is created, and StartMirroring() is called to
+//      begin the mirroring session.  This causes AudioMirroringManager to
+//      instruct any matching Diverters to divert their audio data to the
+//      MirroringDestination.
+//
+// #2 and #3 above may occur in any order, as it is the job of
+// AudioMirroringManager to realize when the players can be "matched up."
+
+#ifndef CONTENT_BROWSER_MEDIA_CAPTURE_AUDIO_MIRRORING_MANAGER_H_
+#define CONTENT_BROWSER_MEDIA_CAPTURE_AUDIO_MIRRORING_MANAGER_H_
+
+#include <map>
+#include <utility>
+
+#include "base/basictypes.h"
+#include "content/common/content_export.h"
+#include "media/audio/audio_source_diverter.h"
+
+namespace media {
+class AudioOutputStream;
+}
+
+namespace content {
+
+class CONTENT_EXPORT AudioMirroringManager {
+ public:
+  // Interface for diverting audio data to an alternative AudioOutputStream.
+  typedef media::AudioSourceDiverter Diverter;
+
+  // Interface to be implemented by audio mirroring destinations.  See comments
+  // for StartMirroring() and StopMirroring() below.
+  class MirroringDestination {
+   public:
+    // Create a consumer of audio data in the format specified by |params|, and
+    // connect it as an input to mirroring.  When Close() is called on the
+    // returned AudioOutputStream, the input is disconnected and the object
+    // becomes invalid.
+    virtual media::AudioOutputStream* AddInput(
+        const media::AudioParameters& params) = 0;
+
+   protected:
+    virtual ~MirroringDestination() {}
+  };
+
+  AudioMirroringManager();
+
+  virtual ~AudioMirroringManager();
+
+  // Add/Remove a diverter for an audio stream with a known RenderView target
+  // (represented by |render_process_id| + |render_view_id|).  Multiple
+  // diverters may be added for the same target.  |diverter| must live until
+  // after RemoveDiverter() is called.
+  //
+  // Re-entrancy warning: These methods should not be called by a Diverter
+  // during a Start/StopDiverting() invocation.
+  virtual void AddDiverter(int render_process_id, int render_view_id,
+                           Diverter* diverter);
+  virtual void RemoveDiverter(int render_process_id, int render_view_id,
+                              Diverter* diverter);
+
+  // Start/stop mirroring all audio output streams associated with a RenderView
+  // target (represented by |render_process_id| + |render_view_id|) to
+  // |destination|.  |destination| must live until after StopMirroring() is
+  // called.
+  virtual void StartMirroring(int render_process_id, int render_view_id,
+                              MirroringDestination* destination);
+  virtual void StopMirroring(int render_process_id, int render_view_id,
+                             MirroringDestination* destination);
+
+ private:
+  // A mirroring target is a RenderView identified by a
+  // <render_process_id, render_view_id> pair.
+  typedef std::pair<int, int> Target;
+
+  // Note: Objects in these maps are not owned.
+  typedef std::multimap<Target, Diverter*> DiverterMap;
+  typedef std::map<Target, MirroringDestination*> SessionMap;
+
+  // Currently-active divertable audio streams.
+  DiverterMap diverters_;
+
+  // Currently-active mirroring sessions.
+  SessionMap sessions_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioMirroringManager);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_MEDIA_CAPTURE_AUDIO_MIRRORING_MANAGER_H_