Handle audio device changes on Mac

media/audio/mac/audio_device_listener_mac.cc

Index: media/audio/mac/audio_device_listener_mac.cc
diff --git a/media/audio/mac/audio_device_listener_mac.cc b/media/audio/mac/audio_device_listener_mac.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f8d44df3deb03f898adf7a582fac530073363251
--- /dev/null
+++ b/media/audio/mac/audio_device_listener_mac.cc
@@ -0,0 +1,53 @@
+// 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/mac/audio_device_listener_mac.h"
+
+#include "base/logging.h"
+
+namespace media {
+
+AudioDeviceListenerMac::AudioDeviceListenerMac(const base::Closure& listener_cb)
+ : listener_cb_(listener_cb) {

[DaleCurtis, 2012/10/29 01:58:45]

4 space indent.

[sail, 2012/10/29 04:21:46]

Done.

+  AudioObjectPropertyAddress property = {
+    kAudioHardwarePropertyDefaultOutputDevice,

[DaleCurtis, 2012/10/29 01:58:45]

Can you add a listener for preferred sample rate as well?  Otherwise
AudioOutputResampler will probably still break.

[sail, 2012/10/29 04:21:46]

Added kAudioDevicePropertyNominalSampleRate.
Do you know how I can test this? I'm not sure if observing
kAudioDevicePropertyNominalSampleRate on kAudioObjectSystemObject will work or
not. Thanks.

+    kAudioObjectPropertyScopeGlobal,
+    kAudioObjectPropertyElementMaster
+  };
+  AudioObjectAddPropertyListener(

[DaleCurtis, 2012/10/29 01:58:45]

Do you need to be error checking these things?

[sail, 2012/10/29 04:21:46]

Done.

+      kAudioObjectSystemObject,
+      &property,
+      &AudioDeviceListenerMac::OnDefaultDeviceChanged,
+      this);
+}
+
+AudioDeviceListenerMac::~AudioDeviceListenerMac() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  AudioObjectPropertyAddress property = {
+    kAudioHardwarePropertyDefaultOutputDevice,
+    kAudioObjectPropertyScopeGlobal,
+    kAudioObjectPropertyElementMaster
+  };
+  AudioObjectRemovePropertyListener(

[DaleCurtis, 2012/10/29 01:58:45]

Ditto?

[sail, 2012/10/29 04:21:46]

Done.

+      kAudioObjectSystemObject,
+      &property,
+      &AudioDeviceListenerMac::OnDefaultDeviceChanged,
+      this);
+}
+
+// static
+OSStatus AudioDeviceListenerMac::OnDefaultDeviceChanged(
+    AudioObjectID object,
+    UInt32 size,
+    const AudioObjectPropertyAddress addresses[],
+    void* context) {
+  AudioDeviceListenerMac* listener =
+      static_cast<AudioDeviceListenerMac*>(context);
+  DCHECK(listener->thread_checker_.CalledOnValidThread());
+  listener->listener_cb_.Run();
+  return noErr;
+}
+
+}  // namespace media