Browser-wide audio mirroring for TabCapture API

media/audio/audio_manager_base.cc

Index: media/audio/audio_manager_base.cc
diff --git a/media/audio/audio_manager_base.cc b/media/audio/audio_manager_base.cc
index 7b79613774c2b66ad3031794daf7810f894a1ddf..1f2f65139d4cb6e0eb399e11c4d32c38723df926 100644
--- a/media/audio/audio_manager_base.cc
+++ b/media/audio/audio_manager_base.cc
@@ -14,6 +14,8 @@
 #include "media/audio/audio_util.h"
 #include "media/audio/fake_audio_input_stream.h"
 #include "media/audio/fake_audio_output_stream.h"
+#include "media/audio/virtual_audio_input_stream.h"
+#include "media/audio/virtual_audio_output_stream.h"
 #include "media/base/media_switches.h"
 
 // TODO(dalecurtis): Temporarily disabled while switching pipeline to use float,
@@ -45,7 +47,8 @@ AudioManagerBase::AudioManagerBase()
       max_num_input_streams_(kDefaultMaxInputStreams),
       num_output_streams_(0),
       num_input_streams_(0),
-      audio_thread_(new base::Thread("AudioThread")) {
+      audio_thread_(new base::Thread("AudioThread")),
+      virtual_audio_input_stream_(NULL) {
 #if defined(OS_WIN)
   audio_thread_->init_com_with_mta(true);
 #endif
@@ -100,7 +103,12 @@ AudioOutputStream* AudioManagerBase::MakeAudioOutputStream(
       !HasAudioOutputDevices();
 
   AudioOutputStream* stream = NULL;
-  if (audio_output_disabled) {
+  if (virtual_audio_input_stream_) {
+    VirtualAudioOutputStream* virtual_stream =
+        VirtualAudioOutputStream::MakeStream(this, params);
+    stream = virtual_stream;
+    virtual_audio_input_stream_->AddOutputStream(virtual_stream, params);
+  } else if (audio_output_disabled) {
     stream = FakeAudioOutputStream::MakeFakeStream(this, params);
   } else if (params.format() == AudioParameters::AUDIO_PCM_LINEAR) {
     stream = MakeLinearOutputStream(params);
@@ -130,7 +138,20 @@ AudioInputStream* AudioManagerBase::MakeAudioInputStream(
   }
 
   AudioInputStream* stream = NULL;
-  if (params.format() == AudioParameters::AUDIO_FAKE) {
+  if (params.format() == AudioParameters::AUDIO_MIRROR_BROWSER) {
+    // TODO(justinlin): Currently, we can only support mirroring audio from 1
+    // tab, so subsequent tab capture requests will just get microphone audio.

[miu, 2012/11/26 21:14:55]

They'll get "FakeAudioInputStream" and not microphone audio, right?

[justinlin, 2012/11/27 22:26:12]

Right, done.

+    // Maybe we should just return the same stream and ref-count, so that we
+    // only actually destroy the stream when there's no mirroring?
+    if (!virtual_audio_input_stream_) {
+      virtual_audio_input_stream_ =
+          VirtualAudioInputStream::MakeStream(this, params);
+      stream = virtual_audio_input_stream_;
+      NotifyAllOutputDeviceChangeListeners();
+    } else {
+      stream = FakeAudioInputStream::MakeFakeStream(this, params);

[no longer working on chromium, 2012/11/26 22:20:07]

why a fake stream is needed? can you return NULL to indicate a failure instead?

[justinlin, 2012/11/27 22:26:12]

I haven't looked at the plumbing closely, but I think if we return null, it
might cause the media request to fail, but we still want it for just video.
Added TODO, and will look.

+    }
+  } else if (params.format() == AudioParameters::AUDIO_FAKE) {
     stream = FakeAudioInputStream::MakeFakeStream(this, params);
   } else if (params.format() == AudioParameters::AUDIO_PCM_LINEAR) {
     stream = MakeLinearInputStream(params, device_id);
@@ -232,18 +253,35 @@ void AudioManagerBase::GetAudioInputDeviceNames(
     media::AudioDeviceNames* device_names) {
 }
 
+void AudioManagerBase::ReleaseVirtualOutputStream(
+    VirtualAudioOutputStream* stream) {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  virtual_audio_input_stream_->RemoveOutputStream(stream);
+  ReleaseOutputStream(stream);
+}
+
 void AudioManagerBase::ReleaseOutputStream(AudioOutputStream* stream) {
+  DCHECK(message_loop_->BelongsToCurrentThread());
   DCHECK(stream);
   // TODO(xians) : Have a clearer destruction path for the AudioOutputStream.
   // For example, pass the ownership to AudioManager so it can delete the
   // streams.
+
   num_output_streams_--;
   delete stream;
 }
 
 void AudioManagerBase::ReleaseInputStream(AudioInputStream* stream) {
+  DCHECK(message_loop_->BelongsToCurrentThread());
   DCHECK(stream);
   // TODO(xians) : Have a clearer destruction path for the AudioInputStream.
+
+  if (virtual_audio_input_stream_ == stream) {
+    virtual_audio_input_stream_->Stop();
+    virtual_audio_input_stream_ = NULL;
+    NotifyAllOutputDeviceChangeListeners();
+  }
+
   num_input_streams_--;
   delete stream;
 }