[Chromecast] Plumbs raw audio through CMA backend.

chromecast/media/audio/cast_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/cast_audio_manager.h"
+
+#include "chromecast/base/task_runner_impl.h"
+#include "chromecast/media/audio/cast_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 {
+const int kDefaultSampleRate = 48000;

[DaleCurtis, 2015/09/18 22:42:36]

You'll probably want to tailor this for your whatever your silicon is using to
avoid any extra resampling.

[alokp, 2015/09/19 03:47:10]

Added TODO to query from media backend.

+
+// Define bounds for the output buffer size (in frames).
+// Note: These values are copied from AudioManagerPulse implementation.
+static const int kMinimumOutputBufferSize = 512;

[DaleCurtis, 2015/09/18 22:42:36]

Up to you if you need these; again whatever the silicon is expecting. I think
512 might be too low for an alsa based product though.

[alokp, 2015/09/19 03:47:10]

Ditto. Thanks for your suggestion.

+static const int kMaximumOutputBufferSize = 8192;
+static const int kDefaultOutputBufferSize = 2048;
+}  // namespace
+
+namespace chromecast {
+namespace media {
+
+CastAudioManager::CastAudioManager(::media::AudioLogFactory* audio_log_factory)
+    : AudioManagerBase(audio_log_factory) {}
+
+CastAudioManager::~CastAudioManager() {
+  Shutdown();
+}
+
+bool CastAudioManager::HasAudioOutputDevices() {
+  return true;
+}
+
+bool CastAudioManager::HasAudioInputDevices() {
+  return false;
+}
+
+void CastAudioManager::ShowAudioInputSettings() {
+  LOG(WARNING) << "No support for input audio devices";
+}
+
+void CastAudioManager::GetAudioInputDeviceNames(
+    ::media::AudioDeviceNames* device_names) {
+  DCHECK(device_names->empty());
+  LOG(WARNING) << "No support for input audio devices";
+}
+
+::media::AudioParameters CastAudioManager::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>
+CastAudioManager::CreateMediaPipelineBackend() {
+  DCHECK(GetTaskRunner()->BelongsToCurrentThread());
+
+  if (!audio_task_runner_)
+    audio_task_runner_.reset(new TaskRunnerImpl());
+
+  MediaPipelineDeviceParams device_params(
+      MediaPipelineDeviceParams::kModeIgnorePts, audio_task_runner_.get());
+  return scoped_ptr<MediaPipelineBackend>(
+      CastMediaShlib::CreateMediaPipelineBackend(device_params));
+}
+
+::media::AudioOutputStream* CastAudioManager::MakeLinearOutputStream(
+    const ::media::AudioParameters& params) {
+  DCHECK_EQ(::media::AudioParameters::AUDIO_PCM_LINEAR, params.format());
+  return new CastAudioOutputStream(params, this);
+}
+
+::media::AudioOutputStream* CastAudioManager::MakeLowLatencyOutputStream(
+    const ::media::AudioParameters& params,
+    const std::string& device_id) {
+  DCHECK_EQ(::media::AudioParameters::AUDIO_PCM_LOW_LATENCY, params.format());
+  return new CastAudioOutputStream(params, this);
+}
+
+::media::AudioInputStream* CastAudioManager::MakeLinearInputStream(
+    const ::media::AudioParameters& params,
+    const std::string& device_id) {
+  LOG(WARNING) << "No support for input audio devices";
+  return nullptr;
+}
+
+::media::AudioInputStream* CastAudioManager::MakeLowLatencyInputStream(
+    const ::media::AudioParameters& params,
+    const std::string& device_id) {
+  LOG(WARNING) << "No support for input audio devices";
+  return nullptr;
+}
+
+::media::AudioParameters CastAudioManager::GetPreferredOutputStreamParameters(
+    const std::string& output_device_id,
+    const ::media::AudioParameters& input_params) {
+  ::media::ChannelLayout channel_layout = ::media::CHANNEL_LAYOUT_STEREO;
+  int sample_rate = kDefaultSampleRate;
+  int buffer_size = kDefaultOutputBufferSize;
+  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();
+    buffer_size = std::min(
+        kMaximumOutputBufferSize,
+        std::max(kMinimumOutputBufferSize, input_params.frames_per_buffer()));
+  }
+
+  ::media::AudioParameters output_params(
+      ::media::AudioParameters::AUDIO_PCM_LOW_LATENCY, channel_layout,
+      sample_rate, bits_per_sample, buffer_size);
+  return output_params;
+}
+
+}  // namespace media
+}  // namespace chromecast