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..4367b3481926a26962a5d38756af3bd58255eef2 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 +103,11 @@ AudioOutputStream* AudioManagerBase::MakeAudioOutputStream(
       !HasAudioOutputDevices();
 
   AudioOutputStream* stream = NULL;
-  if (audio_output_disabled) {
+  if (virtual_audio_input_stream_ &&
+      params.format() != AudioParameters::AUDIO_FAKE) {

[DaleCurtis, 2012/11/28 23:43:18]

Why not fake? Seems there's a use case for a local machine w/o audio and a
device w/ audio?

[justinlin, 2012/11/29 10:08:33]

I thought this "fake device" type was just used for testing (with some
--use_fake_devices flag) and unit tests? If it's also the format when we don't
have audio output devices, then yes let's use it as input too. I guess we can
use it anyway.

+    stream = VirtualAudioOutputStream::MakeStream(this, params,
+                                                  virtual_audio_input_stream_);
+  } else if (audio_output_disabled) {
     stream = FakeAudioOutputStream::MakeFakeStream(this, params);
   } else if (params.format() == AudioParameters::AUDIO_PCM_LINEAR) {
     stream = MakeLinearOutputStream(params);
@@ -130,7 +137,24 @@ AudioInputStream* AudioManagerBase::MakeAudioInputStream(
   }
 
   AudioInputStream* stream = NULL;
-  if (params.format() == AudioParameters::AUDIO_FAKE) {
+  if (params.format() == AudioParameters::AUDIO_MIRROR_BROWSER) {
+    // TODO(justinlin): Currently, audio mirroring will only work for the first
+    // request. Subsequent requests will not get audio.
+    if (!virtual_audio_input_stream_) {
+      virtual_audio_input_stream_ =
+          VirtualAudioInputStream::MakeStream(this, params);
+      stream = virtual_audio_input_stream_;
+
+      // Make all current output streams recreate themselves as
+      // VirtualAudioOutputStreams that will attach to the above
+      // VirtualAudioInputStream.
+      message_loop_->PostTask(FROM_HERE, base::Bind(
+          &AudioManagerBase::NotifyAllOutputDeviceChangeListeners,
+          base::Unretained(this)));
+    } else {
+      stream = NULL;
+    }
+  } 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);
@@ -233,6 +257,7 @@ void AudioManagerBase::GetAudioInputDeviceNames(
 }
 
 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
@@ -242,8 +267,19 @@ void AudioManagerBase::ReleaseOutputStream(AudioOutputStream* 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;
+
+    // Make all audio output streams (which should be virtual) recreate
+    // themselves as regular audio streams to return sound to hardware.
+    NotifyAllOutputDeviceChangeListeners();
+  }
+
   num_input_streams_--;
   delete stream;
 }