Pass more detailed audio hardware configuration information to the renderer

media/audio/mac/audio_unified_mac.cc

Index: media/audio/mac/audio_unified_mac.cc
===================================================================
--- media/audio/mac/audio_unified_mac.cc	(revision 185058)
+++ media/audio/mac/audio_unified_mac.cc	(working copy)
@@ -395,4 +395,95 @@
       output_time);
 }
 
+bool AudioHardwareUnifiedStream::GetDefaultOutputDevice(
+    AudioDeviceID* device) {
+  if (!device)
+    return false;
+
+  // Obtain the current output device selected by the user.
+  AudioObjectPropertyAddress pa;
+  pa.mSelector = kAudioHardwarePropertyDefaultOutputDevice;
+  pa.mScope = kAudioObjectPropertyScopeGlobal;
+  pa.mElement = kAudioObjectPropertyElementMaster;
+
+  UInt32 size = sizeof(*device);
+
+  OSStatus result = AudioObjectGetPropertyData(
+      kAudioObjectSystemObject,
+      &pa,
+      0,
+      0,
+      &size,
+      device);
+
+  if ((result != kAudioHardwareNoError) || (*device == kAudioDeviceUnknown)) {
+    LOG(ERROR) << "Error getting default output AudioDevice.";
+    return false;
+  }
+
+  return true;
+}
+
+bool AudioHardwareUnifiedStream::GetDefaultOutputChannels(
+    int* channels, int* channels_per_frame) {
+  AudioDeviceID device;
+  if (!GetDefaultOutputDevice(&device))
+    return false;
+
+  return GetDeviceChannels(device,
+                           kAudioDevicePropertyScopeOutput,
+                           channels,
+                           channels_per_frame);  
+}
+
+bool AudioHardwareUnifiedStream::GetDeviceChannels(
+    AudioDeviceID device,
+    AudioObjectPropertyScope scope,
+    int* channels,
+    int* channels_per_frame) {
+  if (!channels || !channels_per_frame)
+    return false;
+
+  // Get stream configuration.
+  AudioObjectPropertyAddress pa;
+  pa.mSelector = kAudioDevicePropertyStreamConfiguration;
+  pa.mScope = scope;
+  pa.mElement = kAudioObjectPropertyElementMaster;
+
+  UInt32 size;
+  OSStatus result = AudioObjectGetPropertyDataSize(device, &pa, 0, 0, &size);
+  OSSTATUS_DCHECK(result == noErr, result);
+
+  if (result == noErr && size > 0) {
+    // Allocate storage.
+    scoped_array<uint8> list_storage(new uint8[size]);
+    AudioBufferList& buffer_list =
+        *reinterpret_cast<AudioBufferList*>(list_storage.get());
+
+    result = AudioObjectGetPropertyData(
+        device,
+        &pa,
+        0,
+        0,
+        &size,
+        &buffer_list);
+    OSSTATUS_DCHECK(result == noErr, result);
+
+    if (result == noErr) {
+      // Determine number of input channels.
+      *channels_per_frame = buffer_list.mNumberBuffers > 0 ?
+          buffer_list.mBuffers[0].mNumberChannels : 0;
+      if (*channels_per_frame == 1 && buffer_list.mNumberBuffers > 1) {
+        // Non-interleaved.
+        *channels = buffer_list.mNumberBuffers;
+      } else {
+        // Interleaved.
+        *channels = *channels_per_frame;
+      }
+    }
+  }
+
+  return result == noErr;
+}
+
 }  // namespace media