Add a unified audio I/O backend for ChromeOS.

media/audio/linux/cras_unified.cc

Index: media/audio/linux/cras_unified.cc
diff --git a/media/audio/linux/cras_unified.cc b/media/audio/linux/cras_unified.cc
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+++ b/media/audio/linux/cras_unified.cc
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+// Copyright (c) 2012 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 "media/audio/linux/cras_unified.h"
+
+#include <cras_client.h>
+
+#include "base/logging.h"
+#include "media/audio/audio_util.h"
+#include "media/audio/linux/alsa_util.h"
+#include "media/audio/linux/audio_manager_linux.h"
+
+namespace media {
+
+// TODO(dgreid): support more than hard-coded stereo input.
+// Ideally we would like to receive this value as a constructor argument.
+// crbug.com/147326
+static const int kDefaultInputChannels = 2;
+
+// Overview of operation:
+// 1) An object of CrasUnifiedStream is created by the AudioManager
+// factory: audio_man->MakeAudioStream().
+// 2) Next some thread will call Open(), at that point a client is created and
+// configured for the correct format and sample rate.
+// 3) Then Start(source) is called and a stream is added to the CRAS client
+// which will create its own thread that periodically calls the source for more
+// data as buffers are being consumed.
+// 4) When finished Stop() is called, which is handled by stopping the stream.
+// 5) Finally Close() is called. It cleans up and notifies the audio manager,
+// which likely will destroy this object.
+
+CrasUnifiedStream::CrasUnifiedStream(const AudioParameters& params,
+                                     AudioManagerLinux* manager)
+    : client_(NULL),
+      stream_id_(0),
+      samples_per_packet_(params.frames_per_buffer()),
+      bytes_per_frame_(0),
+      frame_rate_(params.sample_rate()),
+      num_channels_(params.channels()),
+      pcm_format_(alsa_util::BitsToFormat(params.bits_per_sample())),
+      is_playing_(false),
+      volume_(1.0),
+      manager_(manager),
+      source_callback_(NULL),
+      input_bus_(AudioBus::Create(kDefaultInputChannels,
+                 params.frames_per_buffer())),
+      output_bus_(AudioBus::Create(params)) {
+  // We must have a manager.
+  DCHECK(manager_);
+}
+
+CrasUnifiedStream::~CrasUnifiedStream() {
+  DCHECK(!is_playing_);
+}
+
+bool CrasUnifiedStream::Open() {
+  // Sanity check input values.
+  if (frame_rate_ <= 0) {
+    LOG(WARNING) << "Unsupported audio frequency.";
+    return false;
+  }
+
+  if (pcm_format_ == SND_PCM_FORMAT_UNKNOWN) {
+    LOG(WARNING) << "Unsupported pcm format";
+    return false;
+  }
+
+  // Create the client and connect to the CRAS server.
+  int err = cras_client_create(&client_);
+  if (err < 0) {
+    LOG(WARNING) << "Couldn't create CRAS client.\n";
+    client_ = NULL;
+    return false;
+  }
+
+  err = cras_client_connect(client_);
+  if (err) {
+    LOG(WARNING) << "Couldn't connect CRAS client.\n";
+    cras_client_destroy(client_);
+    client_ = NULL;
+    return false;
+  }
+
+  // Then start running the client.
+  err = cras_client_run_thread(client_);
+  if (err) {
+    LOG(WARNING) << "Couldn't run CRAS client.\n";
+    cras_client_destroy(client_);
+    client_ = NULL;
+    return false;
+  }
+
+  return true;
+}
+
+void CrasUnifiedStream::Close() {
+  if (client_) {
+    cras_client_stop(client_);
+    cras_client_destroy(client_);
+    client_ = NULL;
+  }
+
+  // Signal to the manager that we're closed and can be removed.
+  // Should be last call in the method as it deletes "this".
+  manager_->ReleaseOutputStream(this);
+}
+
+void CrasUnifiedStream::Start(AudioSourceCallback* callback) {
+  CHECK(callback);
+  source_callback_ = callback;
+
+  // Only start if we can enter the playing state.
+  if (is_playing_)
+    return;
+
+  // Prepare |audio_format| and |stream_params| for the stream we
+  // will create.
+  cras_audio_format* audio_format = cras_audio_format_create(
+      pcm_format_,
+      frame_rate_,
+      num_channels_);
+  if (audio_format == NULL) {
+    LOG(WARNING) << "Error setting up audio parameters.";
+    callback->OnError(this, -ENOMEM);
+    return;
+  }
+
+  cras_stream_params* stream_params = cras_client_unified_params_create(
+      CRAS_STREAM_UNIFIED,
+      samples_per_packet_,
+      CRAS_STREAM_TYPE_DEFAULT,
+      0,
+      this,
+      CrasUnifiedStream::UnifiedCallback,
+      CrasUnifiedStream::StreamError,
+      audio_format);
+  if (stream_params == NULL) {
+    LOG(WARNING) << "Error setting up stream parameters.";
+    callback->OnError(this, -ENOMEM);
+    cras_audio_format_destroy(audio_format);
+    return;
+  }
+
+  // Before starting the stream, save the number of bytes in a frame for use in
+  // the callback.
+  bytes_per_frame_ = cras_client_format_bytes_per_frame(audio_format);
+
+  // Adding the stream will start the audio callbacks requesting data.
+  int err = cras_client_add_stream(client_, &stream_id_, stream_params);
+  if (err < 0) {
+    LOG(WARNING) << "Failed to add the stream";
+    callback->OnError(this, err);
+    cras_audio_format_destroy(audio_format);
+    cras_client_stream_params_destroy(stream_params);
+    return;
+  }
+
+  // Set initial volume.
+  cras_client_set_stream_volume(client_, stream_id_, volume_);
+
+  // Done with config params.
+  cras_audio_format_destroy(audio_format);
+  cras_client_stream_params_destroy(stream_params);
+
+  is_playing_ = true;
+}
+
+void CrasUnifiedStream::Stop() {
+  if (!client_)
+    return;
+
+  // Removing the stream from the client stops audio.
+  cras_client_rm_stream(client_, stream_id_);
+
+  is_playing_ = false;
+}
+
+void CrasUnifiedStream::SetVolume(double volume) {
+  if (!client_)
+    return;
+  volume_ = static_cast<float>(volume);
+  cras_client_set_stream_volume(client_, stream_id_, volume_);
+}
+
+void CrasUnifiedStream::GetVolume(double* volume) {
+  *volume = volume_;
+}
+
+// Static callback asking for samples.
+int CrasUnifiedStream::UnifiedCallback(cras_client* client,
+                                       cras_stream_id_t stream_id,
+                                       uint8* input_samples,
+                                       uint8* output_samples,
+                                       unsigned int frames,
+                                       const timespec* input_ts,
+                                       const timespec* output_ts,
+                                       void* arg) {
+  CrasUnifiedStream* me = static_cast<CrasUnifiedStream*>(arg);
+  return me->Render(frames, input_samples, output_samples, input_ts, output_ts);
+}
+
+// Static callback for stream errors.
+int CrasUnifiedStream::StreamError(cras_client* client,
+                                   cras_stream_id_t stream_id,
+                                   int err,
+                                   void* arg) {
+  CrasUnifiedStream* me = static_cast<CrasUnifiedStream*>(arg);
+  me->NotifyStreamError(err);
+  return 0;
+}
+
+// Note this is run from a real time thread, so don't waste cycles here.
+uint32 CrasUnifiedStream::Render(size_t frames,
+                                 uint8* input_samples,
+                                 uint8* output_samples,
+                                 const timespec* input_ts,
+                                 const timespec* output_ts) {
+  unsigned int bytes_per_sample = bytes_per_frame_ / num_channels_;
+
+  DCHECK_EQ(frames, static_cast<size_t>(output_bus_->frames()));
+
+  input_bus_->FromInterleaved(input_samples, frames, bytes_per_sample);
+
+  int frames_filled = source_callback_->OnMoreIOData(
+      input_bus_.get(), output_bus_.get(), AudioBuffersState(0, 0));
+
+  output_bus_->ToInterleaved(frames_filled, bytes_per_sample, output_samples);
+
+  return frames_filled;
+}
+
+void CrasUnifiedStream::NotifyStreamError(int err) {
+  // This will remove the stream from the client.
+  if (source_callback_)
+    source_callback_->OnError(this, err);
+}
+
+}  // namespace media