Add a virtual beamforming audio device on ChromeOS.

media/audio/cras/audio_manager_cras.cc

Index: media/audio/cras/audio_manager_cras.cc
diff --git a/media/audio/cras/audio_manager_cras.cc b/media/audio/cras/audio_manager_cras.cc
index 86d12fc39e5d504808b002083b85f9fb15a4b802..d74a20045de7b970cf1047757a3e757e69fb18a5 100644
--- a/media/audio/cras/audio_manager_cras.cc
+++ b/media/audio/cras/audio_manager_cras.cc
@@ -23,28 +23,56 @@
 #undef max
 
 namespace media {
+namespace {
 
-static void AddDefaultDevice(AudioDeviceNames* device_names) {
-  DCHECK(device_names->empty());
+// Maximum number of output streams that can be open simultaneously.
+const int kMaxOutputStreams = 50;
+
+// Default sample rate for input and output streams.
+const int kDefaultSampleRate = 48000;
+
+// Define bounds for the output buffer size.
+const int kMinimumOutputBufferSize = 512;
+const int kMaximumOutputBufferSize = 8192;
 
+// Default input buffer size.
+const int kDefaultInputBufferSize = 1024;
+
+void AddDefaultDevice(AudioDeviceNames* device_names) {
   // Cras will route audio from a proper physical device automatically.
   device_names->push_back(
       AudioDeviceName(AudioManagerBase::kDefaultDeviceName,
                       AudioManagerBase::kDefaultDeviceId));
 }
 
-// Maximum number of output streams that can be open simultaneously.
-static const int kMaxOutputStreams = 50;
+// Returns a mic positions string if the machine has a beamforming capable
+// internal mic and otherwise an empty string.
+std::string MicPositions() {
+  // Get the list of devices from CRAS. An internal mic with a non-empty
+  // positions field indicates the machine has a beamforming capable mic array.
+  chromeos::AudioDeviceList devices;
+  chromeos::CrasAudioHandler::Get()->GetAudioDevices(&devices);
+  for (const auto& device : devices) {
+    if (device.type == chromeos::AUDIO_TYPE_INTERNAL_MIC) {
+      // There should be only one internal mic device.
+      return device.mic_positions;
+    }
+  }
+  return "";
+}
 
-// Default sample rate for input and output streams.
-static const int kDefaultSampleRate = 48000;
+// Returns the name and ID of the virtual beamforming device.
+AudioDeviceName BeamformingDeviceName() {
+  static const char kBeamformingDeviceNameSuffix[] = " with beamforming";
+  static const char kBeamformingDeviceIdSuffix[] = "-beamforming";
 
-// Define bounds for the output buffer size.
-static const int kMinimumOutputBufferSize = 512;
-static const int kMaximumOutputBufferSize = 8192;
+  return AudioDeviceName(std::string(AudioManagerBase::kDefaultDeviceName) +
+                             kBeamformingDeviceNameSuffix,
+                         std::string(AudioManagerBase::kDefaultDeviceId) +
+                             kBeamformingDeviceIdSuffix);
+}
 
-// Default input buffer size.
-static const int kDefaultInputBufferSize = 1024;
+}  // namespace
 
 bool AudioManagerCras::HasAudioOutputDevices() {
   return true;
@@ -62,7 +90,8 @@ bool AudioManagerCras::HasAudioInputDevices() {
 
 AudioManagerCras::AudioManagerCras(AudioLogFactory* audio_log_factory)
     : AudioManagerBase(audio_log_factory),
-      has_keyboard_mic_(false) {
+      has_keyboard_mic_(false),
+      beamforming_device_name_(BeamformingDeviceName()) {

[ajm, 2015/09/03 01:38:42]

Alex, I reverted to storing this as a const member, as I think it's more clear
that the value will never change than calling a function where it's used.

   SetMaxOutputStreamsAllowed(kMaxOutputStreams);
 }
 
@@ -76,6 +105,13 @@ void AudioManagerCras::ShowAudioInputSettings() {
 
 void AudioManagerCras::GetAudioInputDeviceNames(
     AudioDeviceNames* device_names) {
+  mic_positions_ = ParsePointsFromString(MicPositions());
+  // At least two mic positions indicates we have a beamforming capable mic
+  // array. Add the virtual beamforming device to the list. When this device is
+  // queried through GetInputStreamParameters, provide the cached mic positions.
+  if (mic_positions_.size() > 1)
+    device_names->push_back(beamforming_device_name_);
+
   AddDefaultDevice(device_names);
 }
 
@@ -95,11 +131,16 @@ AudioParameters AudioManagerCras::GetInputStreamParameters(
       has_keyboard_mic_ ? AudioParameters::KEYBOARD_MIC
                         : AudioParameters::NO_EFFECTS;
 
+  // Return the cached mic positions in the case of the beamforming device.
+  const std::vector<Point>& mic_positions =
+      device_id == beamforming_device_name_.unique_id ? mic_positions_
+                                                      : std::vector<Point>();
+
   // TODO(hshi): Fine-tune audio parameters based on |device_id|. The optimal
   // parameters for the loopback stream may differ from the default.
-  return AudioParameters(
-      AudioParameters::AUDIO_PCM_LOW_LATENCY, CHANNEL_LAYOUT_STEREO,
-      kDefaultSampleRate, 16, buffer_size, effects);
+  return AudioParameters(AudioParameters::AUDIO_PCM_LOW_LATENCY,
+                         CHANNEL_LAYOUT_STEREO, kDefaultSampleRate, 16,
+                         buffer_size, mic_positions, effects);
 }
 
 void AudioManagerCras::SetHasKeyboardMic() {
@@ -156,9 +197,8 @@ AudioParameters AudioManagerCras::GetPreferredOutputStreamParameters(
   if (user_buffer_size)
     buffer_size = user_buffer_size;
 
-  return AudioParameters(
-      AudioParameters::AUDIO_PCM_LOW_LATENCY, channel_layout,
-      sample_rate, bits_per_sample, buffer_size, AudioParameters::NO_EFFECTS);
+  return AudioParameters(AudioParameters::AUDIO_PCM_LOW_LATENCY, channel_layout,
+                         sample_rate, bits_per_sample, buffer_size);
 }
 
 AudioOutputStream* AudioManagerCras::MakeOutputStream(