[Chromecast] Plumbs raw audio through CMA backend.

chromecast/media/audio/audio_manager.cc

+// Copyright 2015 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 "chromecast/media/audio/audio_manager.h"
+
+#include "chromecast/base/task_runner_impl.h"
+#include "chromecast/media/audio/audio_output_stream.h"
+#include "chromecast/public/cast_media_shlib.h"
+#include "chromecast/public/media/media_pipeline_backend.h"
+#include "chromecast/public/media/media_pipeline_device_params.h"
+
+namespace chromecast {
+namespace media {
+
+AudioManager::AudioManager(::media::AudioLogFactory* audio_log_factory)
+    : AudioManagerBase(audio_log_factory) {}
+
+AudioManager::~AudioManager() {
+  Shutdown();
+}
+
+bool AudioManager::HasAudioOutputDevices() {
+  return true;
+}
+
+bool AudioManager::HasAudioInputDevices() {
+  return false;
+}
+
+void AudioManager::ShowAudioInputSettings() {
+  LOG(WARNING) << "No support for input audio devices";
+}
+
+void AudioManager::GetAudioInputDeviceNames(
+    ::media::AudioDeviceNames* device_names) {
+  DCHECK(device_names->empty());
+  LOG(WARNING) << "No support for input audio devices";
+}
+
+::media::AudioParameters AudioManager::GetInputStreamParameters(
+    const std::string& device_id) {
+  LOG(WARNING) << "No support for input audio devices";
+  // Need to send a valid AudioParameters object even when it will unused.
+  return ::media::AudioParameters(
+      ::media::AudioParameters::AUDIO_PCM_LOW_LATENCY,
+      ::media::CHANNEL_LAYOUT_STEREO, 48000, 16, 1024);
+}
+
+scoped_ptr<MediaPipelineBackend> AudioManager::CreateMediaPipelineBackend() {
+  if (!audio_task_runner_)
+    audio_task_runner_.reset(new TaskRunnerImpl());

[kmackay, 2015/09/01 23:04:47]

We might want to DCHECK that CreateMediaPipelineBackend() is always called on
the same thread.

[alokp, 2015/09/01 23:29:09]

In production it should always be called on the AudioThread. But I do not have
an AudioThread in unittests, so I am not sure how to enforce it. I will see if I
can fake an AudioThread in unittests.

+
+  MediaPipelineDeviceParams device_params(
+      MediaPipelineDeviceParams::kModeIgnorePts, audio_task_runner_.get());
+  return scoped_ptr<MediaPipelineBackend>(
+      CastMediaShlib::CreateMediaPipelineBackend(device_params));
+}
+
+::media::AudioOutputStream* AudioManager::MakeLinearOutputStream(
+    const ::media::AudioParameters& params) {
+  DCHECK_EQ(::media::AudioParameters::AUDIO_PCM_LINEAR, params.format());
+  return new AudioOutputStream(params, this);
+}
+
+::media::AudioOutputStream* AudioManager::MakeLowLatencyOutputStream(
+    const ::media::AudioParameters& params,
+    const std::string& device_id) {
+  DCHECK_EQ(::media::AudioParameters::AUDIO_PCM_LOW_LATENCY, params.format());
+  return new AudioOutputStream(params, this);
+}
+
+::media::AudioInputStream* AudioManager::MakeLinearInputStream(
+    const ::media::AudioParameters& params,
+    const std::string& device_id) {
+  LOG(WARNING) << "No support for input audio devices";
+  return nullptr;
+}
+
+::media::AudioInputStream* AudioManager::MakeLowLatencyInputStream(
+    const ::media::AudioParameters& params,
+    const std::string& device_id) {
+  LOG(WARNING) << "No support for input audio devices";
+  return nullptr;
+}
+
+::media::AudioParameters AudioManager::GetPreferredOutputStreamParameters(
+    const std::string& output_device_id,
+    const ::media::AudioParameters& input_params) {
+  ::media::ChannelLayout channel_layout = ::media::CHANNEL_LAYOUT_STEREO;
+  int sample_rate = 44100;
+  int buffer_size = 2048;
+  int bits_per_sample = 16;
+  if (input_params.IsValid()) {
+    // Do not change:
+    // - the channel layout
+    // - the number of bits per sample
+    // We support stereo only with 16 bits per sample.
+    sample_rate = input_params.sample_rate();
+  }
+
+  ::media::AudioParameters output_params(
+      ::media::AudioParameters::AUDIO_PCM_LOW_LATENCY, channel_layout,
+      sample_rate, bits_per_sample, buffer_size,
+      ::media::AudioParameters::NO_EFFECTS);
+  return output_params;
+}
+
+}  // namespace media
+}  // namespace chromecast