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..9213e4c6db7118ce5c4a88ec1186a9311c55fc7d 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 +138,17 @@ AudioInputStream* AudioManagerBase::MakeAudioInputStream(
   }
 
   AudioInputStream* stream = NULL;
-  if (params.format() == AudioParameters::AUDIO_FAKE) {
+  if (params.format() == AudioParameters::AUDIO_WEB_CONTENTS &&
+      !virtual_audio_input_stream_) {

[DaleCurtis, 2012/11/21 23:45:43]

CHECK(!virtual_audio_input_stream) instead of if ! ?

[justinlin, 2012/11/26 20:19:20]

This brings up that what I wanted to do won't work. Fixed that. See TODO. We'll
just use a fake stream for subsequent mirroring requests.

+    // TODO(justinlin): Currently, we can only support mirroring audio from 1
+    // tab, so subsequent tab capture requests will just get microphone audio.
+    // Maybe we should just return the same stream and ref-count, so that we
+    // only actually destroy the stream when there's no mirroring?
+    virtual_audio_input_stream_ =
+        VirtualAudioInputStream::MakeStream(this, params);
+    stream = virtual_audio_input_stream_;
+    NotifyAllOutputDeviceChangeListeners();
+  } 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);
@@ -237,6 +255,13 @@ void AudioManagerBase::ReleaseOutputStream(AudioOutputStream* stream) {
   // TODO(xians) : Have a clearer destruction path for the AudioOutputStream.
   // For example, pass the ownership to AudioManager so it can delete the
   // streams.
+
+  if (virtual_audio_input_stream_) {

[DaleCurtis, 2012/11/21 23:45:43]

Hmmm, this seems incorrect. You set virtual_audio_input_stream_ above but then
fire NotifyAllOutputDeviceChangeListeners() which means non
VirtualAudioOutputStream's will be calling this method.

[justinlin, 2012/11/26 20:19:20]

Done. Added another release method for virtual output streams.

+    VirtualAudioOutputStream* virtual_stream =
+        static_cast<VirtualAudioOutputStream*>(stream);
+    virtual_audio_input_stream_->RemoveOutputStream(virtual_stream);
+  }
+
   num_output_streams_--;
   delete stream;
 }
@@ -244,6 +269,13 @@ void AudioManagerBase::ReleaseOutputStream(AudioOutputStream* stream) {
 void AudioManagerBase::ReleaseInputStream(AudioInputStream* stream) {

[DaleCurtis, 2012/11/21 23:45:43]

Is this method guaranteed to happen on the audio thread? If so can you
DCHECK(belongs to current thread) ?

[justinlin, 2012/11/26 20:19:20]

Done.

   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;
 }