Allow audio system to handle synchronized low-latency audio I/O

media/audio/audio_output_device.cc

 // 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/audio_output_device.h"
 
 #include "base/debug/trace_event.h"
 #include "base/message_loop.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/time.h"
 #include "media/audio/audio_output_controller.h"
 #include "media/audio/audio_util.h"
 #include "media/audio/shared_memory_util.h"
+#include "media/base/limits.h"
 
 namespace media {
 
 // Takes care of invoking the render callback on the audio thread.
 // An instance of this class is created for each capture stream in
 // OnStreamCreated().
 class AudioOutputDevice::AudioThreadCallback
     : public AudioDeviceThread::Callback {
  public:
   AudioThreadCallback(const AudioParameters& audio_parameters,
+                      int input_channels,
                       base::SharedMemoryHandle memory,
                       int memory_length,
                       AudioRendererSink::RenderCallback* render_callback);
   virtual ~AudioThreadCallback();
 
   virtual void MapSharedMemory() OVERRIDE;
 
   // Called whenever we receive notifications about pending data.
   virtual void Process(int pending_data) OVERRIDE;
 
  private:
   AudioRendererSink::RenderCallback* render_callback_;
-  scoped_ptr<AudioBus> audio_bus_;
+  scoped_ptr<AudioBus> input_bus_;
+  scoped_ptr<AudioBus> output_bus_;
   DISALLOW_COPY_AND_ASSIGN(AudioThreadCallback);
 };
 
 AudioOutputDevice::AudioOutputDevice(
     AudioOutputIPC* ipc,
     const scoped_refptr<base::MessageLoopProxy>& io_loop)
     : ScopedLoopObserver(io_loop),
+      input_channels_(0),
       callback_(NULL),
       ipc_(ipc),
       stream_id_(0),
       play_on_start_(true),
       is_started_(false) {
   CHECK(ipc_);
 }
 
 void AudioOutputDevice::Initialize(const AudioParameters& params,
                                    RenderCallback* callback) {
   CHECK_EQ(0, stream_id_) <<
       "AudioOutputDevice::Initialize() must be called before Start()";
 
   CHECK(!callback_);  // Calling Initialize() twice?
 
   audio_parameters_ = params;
   callback_ = callback;
 }
 
+void AudioOutputDevice::InitializeIO(const AudioParameters& params,
+                                     int input_channels,

[DaleCurtis, 2012/09/11 09:44:39]

Does it make sense to bite the bullet and have an "AudioParameters input_params"
everywhere? 

+                                     RenderCallback* callback) {
+  DCHECK_GE(input_channels, 0);
+  DCHECK_LT(input_channels, limits::kMaxChannels);
+  input_channels_ = input_channels;
+  Initialize(params, callback);
+}
+
 AudioOutputDevice::~AudioOutputDevice() {
   // The current design requires that the user calls Stop() before deleting
   // this class.
   CHECK_EQ(0, stream_id_);
 }
 
 void AudioOutputDevice::Start() {
   DCHECK(callback_) << "Initialize hasn't been called";
   message_loop()->PostTask(FROM_HERE,
       base::Bind(&AudioOutputDevice::CreateStreamOnIOThread, this,
-                 audio_parameters_));
+                 audio_parameters_, input_channels_));
 }
 
 void AudioOutputDevice::Stop() {
   {
     base::AutoLock auto_lock(audio_thread_lock_);
     audio_thread_.Stop(MessageLoop::current());
   }
 
   message_loop()->PostTask(FROM_HERE,
       base::Bind(&AudioOutputDevice::ShutDownOnIOThread, this));
@@ skipping 14 matching lines @@
     return false;
 
   if (!message_loop()->PostTask(FROM_HERE,
           base::Bind(&AudioOutputDevice::SetVolumeOnIOThread, this, volume))) {
     return false;
   }
 
   return true;
 }
 
-void AudioOutputDevice::CreateStreamOnIOThread(const AudioParameters& params) {
+void AudioOutputDevice::CreateStreamOnIOThread(const AudioParameters& params,
+                                               int input_channels) {
   DCHECK(message_loop()->BelongsToCurrentThread());
   // Make sure we don't create the stream more than once.
   DCHECK_EQ(0, stream_id_);
   if (stream_id_)
     return;
 
   stream_id_ = ipc_->AddDelegate(this);
-  ipc_->CreateStream(stream_id_, params);
+  ipc_->CreateStream(stream_id_, params, input_channels);
 }
 
 void AudioOutputDevice::PlayOnIOThread() {
   DCHECK(message_loop()->BelongsToCurrentThread());
   if (stream_id_ && is_started_)
     ipc_->PlayStream(stream_id_);
   else
     play_on_start_ = true;
 }
 
@@ skipping 80 matching lines @@
   // the IPC layer should have closed the shared memory and socket handles
   // for us and not invoked the callback.  The basic assertion is that when
   // stream_id_ is 0 the AudioOutputDevice instance is not registered as a
   // delegate and hence it should not receive callbacks.
   DCHECK(stream_id_);
 
   base::AutoLock auto_lock(audio_thread_lock_);
 
   DCHECK(audio_thread_.IsStopped());
   audio_callback_.reset(new AudioOutputDevice::AudioThreadCallback(
-      audio_parameters_, handle, length, callback_));
+      audio_parameters_, input_channels_, handle, length, callback_));
   audio_thread_.Start(audio_callback_.get(), socket_handle,
       "AudioOutputDevice");
 
   // We handle the case where Play() and/or Pause() may have been called
   // multiple times before OnStreamCreated() gets called.
   is_started_ = true;
   if (play_on_start_)
     PlayOnIOThread();
 }
 
 void AudioOutputDevice::OnIPCClosed() {
   ipc_ = NULL;
 }
 
 void AudioOutputDevice::WillDestroyCurrentMessageLoop() {
   LOG(ERROR) << "IO loop going away before the audio device has been stopped";
   ShutDownOnIOThread();
 }
 
 // AudioOutputDevice::AudioThreadCallback
 
 AudioOutputDevice::AudioThreadCallback::AudioThreadCallback(
     const AudioParameters& audio_parameters,
+    int input_channels,
     base::SharedMemoryHandle memory,
     int memory_length,
     AudioRendererSink::RenderCallback* render_callback)
-    : AudioDeviceThread::Callback(audio_parameters, memory, memory_length),
+    : AudioDeviceThread::Callback(audio_parameters,
+                                  input_channels,
+                                  memory,
+                                  memory_length),
       render_callback_(render_callback) {
 }
 
 AudioOutputDevice::AudioThreadCallback::~AudioThreadCallback() {
 }
 
 void AudioOutputDevice::AudioThreadCallback::MapSharedMemory() {
   shared_memory_.Map(TotalSharedMemorySizeInBytes(memory_length_));
-  DCHECK_EQ(memory_length_, AudioBus::CalculateMemorySize(audio_parameters_));
-  audio_bus_ = AudioBus::WrapMemory(audio_parameters_, shared_memory_.memory());
+
+  // Calculate output and input memory size.
+  int output_memory_size = AudioBus::CalculateMemorySize(audio_parameters_);
+  int frames = audio_parameters_.frames_per_buffer();
+  int input_memory_size =
+      AudioBus::CalculateMemorySizeFromChannels(input_channels_, frames, NULL);
+
+  int io_size = output_memory_size + input_memory_size;
+
+  DCHECK_EQ(memory_length_, io_size);
+
+  output_bus_ =
+      AudioBus::WrapMemory(audio_parameters_, shared_memory_.memory());
+
+  if (input_channels_ > 0) {
+    // The input data is after the output data.
+    char* input_data =
+        static_cast<char*>(shared_memory_.memory()) + output_memory_size;
+    input_bus_ =
+        AudioBus::WrapMemory(input_channels_, frames, input_data);
+  }
 }
 
 // Called whenever we receive notifications about pending data.
 void AudioOutputDevice::AudioThreadCallback::Process(int pending_data) {
   if (pending_data == kPauseMark) {
     memset(shared_memory_.memory(), 0, memory_length_);
     SetActualDataSizeInBytes(&shared_memory_, memory_length_, 0);
     return;
   }
 
   // Convert the number of pending bytes in the render buffer
   // into milliseconds.
   int audio_delay_milliseconds = pending_data / bytes_per_ms_;
 
   TRACE_EVENT0("audio", "AudioOutputDevice::FireRenderCallback");
 
   // Update the audio-delay measurement then ask client to render audio.  Since
-  // |audio_bus_| is wrapping the shared memory the Render() call is writing
+  // |output_bus_| is wrapping the shared memory the Render() call is writing
   // directly into the shared memory.
-  size_t num_frames = render_callback_->Render(
-      audio_bus_.get(), audio_delay_milliseconds);
+  size_t num_frames = audio_parameters_.frames_per_buffer();
+
+  if (input_bus_.get() && input_channels_ > 0) {
+    render_callback_->RenderIO(input_bus_.get(),
+                               output_bus_.get(),
+                               audio_delay_milliseconds);
+  } else {
+    num_frames = render_callback_->Render(output_bus_.get(),
+                                          audio_delay_milliseconds);
+  }
 
   // Let the host know we are done.
   // TODO(dalecurtis): Technically this is not always correct.  Due to channel
   // padding for alignment, there may be more data available than this.  We're
   // relying on AudioSyncReader::Read() to parse this with that in mind.  Rename
   // these methods to Set/GetActualFrameCount().
   SetActualDataSizeInBytes(
       &shared_memory_, memory_length_,
-      num_frames * sizeof(*audio_bus_->channel(0)) * audio_bus_->channels());
+      num_frames * sizeof(*output_bus_->channel(0)) * output_bus_->channels());
 }
 
 }  // namespace media.