Pass more detailed audio hardware configuration information to the renderer

media/audio/mac/audio_manager_mac.cc

Index: media/audio/mac/audio_manager_mac.cc
===================================================================
--- media/audio/mac/audio_manager_mac.cc	(revision 186233)
+++ media/audio/mac/audio_manager_mac.cc	(working copy)
@@ -23,6 +23,7 @@
 #include "media/base/channel_layout.h"
 #include "media/base/limits.h"
 #include "media/base/media_switches.h"
+#include "media/ffmpeg/ffmpeg_common.h"

[DaleCurtis, 2013/03/07 02:41:39]

You can't include this here which is why I said the method should be moved to
channel_layout. ffmpeg_common pulls in a bunch of FFmpeg dependencies.

[Chris Rogers, 2013/03/09 01:37:50]

Ah I didn't understand what you had meant before - Fixed :)

 
 namespace media {
 
@@ -263,6 +264,99 @@
   return HasAudioHardware(kAudioHardwarePropertyDefaultInputDevice);
 }
 
+// TODO(crogers): There are several places on the OSX specific code which
+// could benefit from this helper function.
+bool AudioManagerMac::GetDefaultOutputDevice(
+    AudioDeviceID* device) {
+  if (!device)

[DaleCurtis, 2013/03/07 02:41:39]

CHECK().

[Chris Rogers, 2013/03/09 01:37:50]

Done.

+    return false;
+
+  // Obtain the current output device selected by the user.
+  AudioObjectPropertyAddress pa;

[DaleCurtis, 2013/03/07 02:41:39]

static const this like:

 static const AudioObjectPropertyAddress kAddress = {
    kAudioHardwarePropertyDefaultOutputDevice,
    kAudioObjectPropertyScopeGlobal,
    kAudioObjectPropertyElementMaster
  };

[Chris Rogers, 2013/03/09 01:37:50]

Done.

+  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.";

[DaleCurtis, 2013/03/07 02:41:39]

DLOG?

[Chris Rogers, 2013/03/09 01:37:50]

Done.

+    return false;
+  }
+
+  return true;
+}
+
+bool AudioManagerMac::GetDefaultOutputChannels(
+    int* channels, int* channels_per_frame) {
+  AudioDeviceID device;
+  if (!GetDefaultOutputDevice(&device))
+    return false;
+
+  return GetDeviceChannels(device,
+                           kAudioDevicePropertyScopeOutput,
+                           channels,
+                           channels_per_frame);
+}
+
+bool AudioManagerMac::GetDeviceChannels(
+    AudioDeviceID device,
+    AudioObjectPropertyScope scope,
+    int* channels,
+    int* channels_per_frame) {

[DaleCurtis, 2013/03/07 02:41:39]

Nothing seems to be using this? Drop for now?

[Chris Rogers, 2013/03/09 01:37:50]

It will soon be using it (AudioHardwareUnifiedStream) so leaving as is.

+  if (!channels || !channels_per_frame)

[DaleCurtis, 2013/03/07 02:41:39]

these should be CHECK().

[Chris Rogers, 2013/03/09 01:37:50]

Done.

+    return false;
+
+  // Get stream configuration.
+  AudioObjectPropertyAddress pa;

[DaleCurtis, 2013/03/07 02:41:39]

Same static const comment.

[Chris Rogers, 2013/03/09 01:37:50]

It can't be static const because the scope is set from a method arg, leaving as
is.

+  pa.mSelector = kAudioDevicePropertyStreamConfiguration;
+  pa.mScope = scope;
+  pa.mElement = kAudioObjectPropertyElementMaster;
+
+  UInt32 size;
+  OSStatus result = AudioObjectGetPropertyDataSize(device, &pa, 0, 0, &size);
+  OSSTATUS_DCHECK(result == noErr, result);

[DaleCurtis, 2013/03/07 02:41:39]

Don't DCHECK, this should just return false.

[Chris Rogers, 2013/03/09 01:37:50]

Done.

+
+  if (result == noErr && size > 0) {

[DaleCurtis, 2013/03/07 02:41:39]

early return instead of indenting the entire next section.

[Chris Rogers, 2013/03/09 01:37:50]

Done.

+    // 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);

[DaleCurtis, 2013/03/07 02:41:39]

Ditto.

[Chris Rogers, 2013/03/09 01:37:50]

Done.

+
+    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;
+}
+
 void AudioManagerMac::GetAudioInputDeviceNames(
     media::AudioDeviceNames* device_names) {
   GetAudioDeviceInfo(true, device_names);
@@ -336,10 +430,14 @@
 
 AudioParameters AudioManagerMac::GetPreferredOutputStreamParameters(
     const AudioParameters& input_params) {
-  ChannelLayout channel_layout = CHANNEL_LAYOUT_STEREO;
+  int hardware_channels = 2;
+  int hardware_channels_per_frame;
+  GetDefaultOutputChannels(&hardware_channels, &hardware_channels_per_frame);
+
+  ChannelLayout channel_layout = GuessChannelLayout(hardware_channels);

[DaleCurtis, 2013/03/07 02:41:39]

Hmm, this isn't what I thought you wanted. This will guess layout for any
channel count. Don't you only want to guess the layout when input_params !=
DISCRETE?

[Chris Rogers, 2013/03/09 01:37:50]

Actually, I'm just being consistent with the AudioManagerWin WASAPI case where
it doesn't use the passed in channel_layout, but instead is militant and insists
to use the hardware layout.

I'd rather become more like the WASAPI case.  It turns out that the
CHANNEL_LAYOUT_DISCRETE layout will be passed in from AudioOutputDevice and the
ChannelMixer will use discrete mixing even though the manager says it's a real
channel layout.

The code in the renderer side to pass in CHANNEL_LAYOUT_DISCRETE from WebAudio
is not yet there yet, so that may not be obvious, but that's the plan...

+
   int input_channels = 0;
   if (input_params.IsValid()) {
-    channel_layout = input_params.channel_layout();
     input_channels = input_params.input_channels();
 
     if (CommandLine::ForCurrentProcess()->HasSwitch(
@@ -352,10 +450,18 @@
     }
   }
 
-  return AudioParameters(
-      AudioParameters::AUDIO_PCM_LOW_LATENCY, channel_layout, input_channels,
-      AUAudioOutputStream::HardwareSampleRate(), 16,
+  AudioParameters params(
+      AudioParameters::AUDIO_PCM_LOW_LATENCY,
+      channel_layout,
+      input_channels,
+      AUAudioOutputStream::HardwareSampleRate(),
+      16,
       kDefaultLowLatencyBufferSize);
+
+  if (channel_layout == CHANNEL_LAYOUT_UNSUPPORTED)

[DaleCurtis, 2013/03/07 02:41:39]

DISCRETE?

[Chris Rogers, 2013/03/09 01:37:50]

Actually, I think that's right because GuessChannelLayout() can return
CHANNEL_LAYOUT_UNSUPPORTED, so I'm just trying to translate that to a sane
setting which falls back to discrete.  It should never happen for any channel
layouts <= 8 channels, but for large numbers of channels it will.

+    params.SetDiscreteChannels(hardware_channels);
+
+  return params;
 }
 
 void AudioManagerMac::CreateDeviceListener() {