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

media/audio/audio_output_controller.cc

 // 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.
 
 #include "media/audio/audio_output_controller.h"
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/message_loop.h"
 #include "base/synchronization/waitable_event.h"
@@ skipping 11 matching lines @@
 
 // Polling-related constants.
 const int AudioOutputController::kPollNumAttempts = 3;
 const int AudioOutputController::kPollPauseInMilliseconds = 3;
 
 AudioOutputController::AudioOutputController(AudioManager* audio_manager,
                                              EventHandler* handler,
                                              const AudioParameters& params,
                                              SyncReader* sync_reader)
     : audio_manager_(audio_manager),
+      params_(params),
       handler_(handler),
       stream_(NULL),
+      diverting_to_stream_(NULL),
       volume_(1.0),
       state_(kEmpty),
       sync_reader_(sync_reader),
       message_loop_(audio_manager->GetMessageLoop()),
       number_polling_attempts_left_(0),
-      params_(params),
       ALLOW_THIS_IN_INITIALIZER_LIST(weak_this_(this)) {
 }
 
 AudioOutputController::~AudioOutputController() {
   DCHECK_EQ(kClosed, state_);
 
   if (message_loop_->BelongsToCurrentThread()) {
     DoStopCloseAndClearStream(NULL);
   } else {
     // http://crbug.com/120973
@@ skipping 13 matching lines @@
     AudioManager* audio_manager,
     EventHandler* event_handler,
     const AudioParameters& params,
     SyncReader* sync_reader) {
   DCHECK(audio_manager);
   DCHECK(sync_reader);
 
   if (!params.IsValid() || !audio_manager)
     return NULL;
 
-  // Starts the audio controller thread.
   scoped_refptr<AudioOutputController> controller(new AudioOutputController(
       audio_manager, event_handler, params, sync_reader));
-
   controller->message_loop_->PostTask(FROM_HERE, base::Bind(
       &AudioOutputController::DoCreate, controller));
-
   return controller;
 }
 
 void AudioOutputController::Play() {
   DCHECK(message_loop_);
   message_loop_->PostTask(FROM_HERE, base::Bind(
       &AudioOutputController::DoPlay, this));
 }
 
 void AudioOutputController::Pause() {
@@ skipping 23 matching lines @@
 
 void AudioOutputController::DoCreate() {
   DCHECK(message_loop_->BelongsToCurrentThread());
 
   // Close() can be called before DoCreate() is executed.
   if (state_ == kClosed)
     return;
   DCHECK(state_ == kEmpty || state_ == kRecreating) << state_;
 
   DoStopCloseAndClearStream(NULL);
-  stream_ = audio_manager_->MakeAudioOutputStreamProxy(params_);
+  stream_ = diverting_to_stream_ ? diverting_to_stream_ :
+      audio_manager_->MakeAudioOutputStreamProxy(params_);
   if (!stream_) {
     state_ = kError;
 
     // TODO(hclam): Define error types.
     handler_->OnError(this, 0);
     return;
   }
 
   if (!stream_->Open()) {
     state_ = kError;
     DoStopCloseAndClearStream(NULL);
 
     // TODO(hclam): Define error types.
     handler_->OnError(this, 0);
     return;
   }
 
-  // Everything started okay, so register for state change callbacks if we have
-  // not already done so.
-  if (state_ != kRecreating)
+  // Everything started okay, so re-register for state change callbacks if
+  // stream_ was created via AudioManager.  Note: The call to
+  // DoStopCloseAndClearStream() above called
+  // RemoveOutputDeviceChangeListener().
+  if (stream_ != diverting_to_stream_)
     audio_manager_->AddOutputDeviceChangeListener(this);
 
   // We have successfully opened the stream. Set the initial volume.
   stream_->SetVolume(volume_);
 
   // Finally set the state to kCreated.
   State original_state = state_;
   state_ = kCreated;
 
   // And then report we have been created if we haven't done so already.
@@ skipping 187 matching lines @@
   // Handle error on the audio controller thread.
   message_loop_->PostTask(FROM_HERE, base::Bind(
       &AudioOutputController::DoReportError, this, code));
 }
 
 void AudioOutputController::DoStopCloseAndClearStream(WaitableEvent* done) {
   DCHECK(message_loop_->BelongsToCurrentThread());
 
   // Allow calling unconditionally and bail if we don't have a stream_ to close.
   if (stream_) {
+    // De-register from state change callbacks if stream_ was created via
+    // AudioManager.
+    if (stream_ != diverting_to_stream_)
+      audio_manager_->RemoveOutputDeviceChangeListener(this);
+
     stream_->Stop();
     stream_->Close();
+    if (stream_ == diverting_to_stream_)
+      diverting_to_stream_ = NULL;
     stream_ = NULL;
 
-    audio_manager_->RemoveOutputDeviceChangeListener(this);
-    audio_manager_ = NULL;
-
     weak_this_.InvalidateWeakPtrs();
   }
 
   // Should be last in the method, do not touch "this" from here on.
   if (done)
     done->Signal();
 }
 
 void AudioOutputController::OnDeviceChange() {
   DCHECK(message_loop_->BelongsToCurrentThread());
 
-  // We should always have a stream by this point.
-  CHECK(stream_);
-
-  // Preserve the original state and shutdown the stream.
-  State original_state = state_;
-  stream_->Stop();
-  stream_->Close();
-  stream_ = NULL;
-
-  // Recreate the stream, exit if we ran into an error.
+  // Recreate the stream (DoCreate() will first shut down an existing stream).
+  // Exit if we ran into an error.
+  const State original_state = state_;
   state_ = kRecreating;

[DaleCurtis, 2012/12/17 20:00:47]

Is this state necessary anymore? Should DoStopCloseAndClearStream just set
state_ = kEmpty?

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

Yes, it's still necessary.  The code on line 155 uses the kRecreating state to
prevent an extra call to handler_->OnCreated(this).

   DoCreate();
   if (!stream_ || state_ == kError)
     return;
 
   // Get us back to the original state or an equivalent state.
   switch (original_state) {
     case kStarting:
     case kPlaying:
       DoPlay();
       return;
     case kCreated:
     case kPausedWhenStarting:
     case kPaused:
       // From the outside these three states are equivalent.
       return;
     default:
       NOTREACHED() << "Invalid original state.";
   }
 }
 
+void AudioOutputController::DivertToStream(AudioOutputStream* to_stream) {
+  if (!message_loop_->BelongsToCurrentThread()) {

[DaleCurtis, 2012/12/17 20:00:47]

Which threads will be calling this?

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

The IO thread (from AudioRendererHost).  Added ThreadChecker to guarantee
single-thread use of these methods.

+    message_loop_->PostTask(
+        FROM_HERE,
+        base::Bind(&AudioOutputController::DivertToStream, this, to_stream));
+    return;
+  }
+
+  DCHECK(!diverting_to_stream_);
+  diverting_to_stream_ = to_stream;

[DaleCurtis, 2012/12/17 20:00:47]

I suspect this might have issues if it gets fired as shutdown is starting. You
might consider explicitly checking state and bailing if it's not okay.

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

See DCHECK one line down.  ;-)

+  DCHECK_NE(kClosed, state_);
+  OnDeviceChange();
+}
+
+void AudioOutputController::RevertDiversion() {
+  if (!message_loop_->BelongsToCurrentThread()) {

[DaleCurtis, 2012/12/17 20:00:47]

Ditto.

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

Done.

+    message_loop_->PostTask(
+        FROM_HERE, base::Bind(&AudioOutputController::RevertDiversion, this));
+    return;
+  }
+
+  if (state_ != kClosed) {
+    OnDeviceChange();
+    DCHECK(!diverting_to_stream_);
+  }
+}
+
 }  // namespace media