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

content/browser/renderer_host/media/audio_renderer_host.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.
 //
 // AudioRendererHost serves audio related requests from AudioRenderer which
 // lives inside the render process and provide access to audio hardware.
 //
 // This class is owned by BrowserRenderProcessHost, and instantiated on UI
 // thread, but all other operations and method calls happen on IO thread, so we
 // need to be extra careful about the lifetime of this object. AudioManager is a
@@ skipping 22 matching lines @@
 //      v                               v
 
 // A SyncSocket pair is used to signal buffer readiness between processes.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_RENDERER_HOST_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_RENDERER_HOST_H_
 
 #include <map>
 
 #include "base/gtest_prod_util.h"
+#include "base/lazy_instance.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/process.h"
 #include "base/sequenced_task_runner_helpers.h"
 #include "base/shared_memory.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/browser_message_filter.h"
 #include "content/public/browser/browser_thread.h"
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_output_controller.h"
 #include "media/audio/simple_sources.h"
 
 namespace media {
 class AudioManager;
 class AudioParameters;
 }
 
 namespace content {
 
 class MediaObserver;
 class ResourceContext;
 
 class CONTENT_EXPORT AudioRendererHost
     : public BrowserMessageFilter,
       public media::AudioOutputController::EventHandler {
  public:
+  // Interface to be implemented by audio mirroring destinations.  See
+  // comments for StartMirroring() and StopMirroring() below.
+  class MirroringDestination
+      : public base::RefCountedThreadSafe<MirroringDestination> {

[DaleCurtis, 2012/12/05 23:35:14]

Do we really need this to be ref counted?

[miu, 2012/12/11 02:30:45]

Yes.  AudioRendererHost operates mainly on the IO thread while
MirroringDestination (to implemented by WebContentsAudioInputStream) will
operate mainly on the audio thread.  Without the ref-counting to guarantee the
object lifetime of MirroringDestination, there are several places where we'd
have to block one thread, waiting for a task to run on the other.

+   public:
+    // Begin pulling data from |callback|, which is providing data in the format
+    // specified by |params|.
+    virtual void AddInput(
+        media::AudioOutputStream::AudioSourceCallback* callback,
+        const media::AudioParameters& params) = 0;
+
+    // Stop pulling data from |callback|.  After this method returns, the caller
+    // can safely destroy the callback.
+    virtual void RemoveInput(
+        media::AudioOutputStream::AudioSourceCallback* callback) = 0;
+
+   protected:
+    friend class base::RefCountedThreadSafe<MirroringDestination>;
+    virtual ~MirroringDestination();
+  };
+
   // Called from UI thread from the owner of this object.
-  AudioRendererHost(media::AudioManager* audio_manager,
+  AudioRendererHost(int render_process_id,
+                    media::AudioManager* audio_manager,
                     MediaObserver* media_observer);
 
   // BrowserMessageFilter implementation.
+  virtual void OnChannelConnected(int32 peer_pid) OVERRIDE;

[DaleCurtis, 2012/12/05 23:35:14]

What is a peer_id?

[miu, 2012/12/11 02:30:45]

The process ID (operating system PID?) of the process at the other end of the
IPC channel.  It doesn't actually matter for our purposes here.  We're just
overriding this method to get notified when the IPC channel is up-and-running.

[tommi (sloooow) - chröme, 2012/12/18 13:41:25]

is int32 needed or is int enough?

[miu, 2012/12/19 00:22:57]

The method signature should probably match what's in BrowserMessageFilter on all
platforms, so int32.  It no longer matters, however, as I don't need this
override anymore.

   virtual void OnChannelClosing() OVERRIDE;
   virtual void OnDestruct() const OVERRIDE;
   virtual bool OnMessageReceived(const IPC::Message& message,
                                  bool* message_was_ok) OVERRIDE;
 
   // AudioOutputController::EventHandler implementations.
   virtual void OnCreated(media::AudioOutputController* controller) OVERRIDE;
   virtual void OnPlaying(media::AudioOutputController* controller) OVERRIDE;
   virtual void OnPaused(media::AudioOutputController* controller) OVERRIDE;
   virtual void OnError(media::AudioOutputController* controller,
                        int error_code) OVERRIDE;
 
+  // Start/stop mirroring all audio output streams associated with
+  // |render_process_id| + |render_view_id| to |destination|.  Any call to
+  // StartMirroring() must be paired with a later call to StopMirroring() since
+  // a reference is held on the MirroringDestination while the mirroring session
+  // is active.
+  static void StartMirroring(
+      int render_process_id, int render_view_id,
+      const scoped_refptr<MirroringDestination>& destination);
+  static void StopMirroring(
+      int render_process_id, int render_view_id,
+      const scoped_refptr<MirroringDestination>& destination);
+
  private:
   friend class AudioRendererHostTest;
   friend class BrowserThread;
   friend class base::DeleteHelper<AudioRendererHost>;
   friend class MockAudioRendererHost;
   FRIEND_TEST_ALL_PREFIXES(AudioRendererHostTest, CreateMockStream);
   FRIEND_TEST_ALL_PREFIXES(AudioRendererHostTest, MockStreamDataConversation);
 
   struct AudioEntry;
   typedef std::map<int, AudioEntry*> AudioEntryMap;
+  typedef std::map<int, scoped_refptr<MirroringDestination> > MirrorSessionMap;
+  typedef std::map<int, AudioRendererHost*> ActiveHostMap;

[tommi (sloooow) - chröme, 2012/12/18 13:41:25]

can you add a note about AudioRendererHost ownership?

[miu, 2012/12/19 00:22:57]

Done.  (in audio_mirroring_manager.h)

 
   virtual ~AudioRendererHost();
 
   // Methods called on IO thread ----------------------------------------------
 
   // Audio related IPC message handlers.
   // Creates an audio output stream with the specified format. If this call is
   // successful this object would keep an internal entry of the stream for the
   // required properties.
   void OnCreateStream(int stream_id,
@@ skipping 51 matching lines @@
   // Returns NULL if not found.
   AudioEntry* LookupById(int stream_id);
 
   // Search for a AudioEntry having the reference to |controller|.
   // This method is used to look up an AudioEntry after a controller
   // event is received.
   AudioEntry* LookupByController(media::AudioOutputController* controller);
 
   media::AudioOutputController* LookupControllerByIdForTesting(int stream_id);
 
+  // Global look-up for the AudioRendererHost instance owned by the
+  // RenderProcessHost specified by |render_process_id|.
+  static AudioRendererHost* FromRenderProcessID(int render_process_id);
+
+  // Implementations for StartMirroring() and StopMirroring() that are run on
+  // the IO BrowserThread.
+  static void DoStartMirroring(
+      int render_process_id, int render_view_id,
+      const scoped_refptr<MirroringDestination>& destination);
+  static void DoStopMirroring(
+      int render_process_id, int render_view_id,
+      const scoped_refptr<MirroringDestination>& destination);
+
+  // ID of the RenderProcessHost that owns this instance.
+  const int render_process_id_;
+
   // A map of stream IDs to audio sources.
   AudioEntryMap audio_entries_;
 
+  // A map of render view IDs to the destination for active mirroring sessions.
+  MirrorSessionMap mirror_sessions_;
+
   media::AudioManager* audio_manager_;
   MediaObserver* media_observer_;
 
+  // Global look-up map for currently-active (i.e., IPC channel is open)
+  // AudioRendererHosts.
+  static base::LazyInstance<ActiveHostMap>::Leaky g_host_map_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioRendererHost);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_RENDERER_HOST_H_