Use multiple shared memory buffers cyclically for audio capture.

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,
-                      base::SharedMemoryHandle memory,
+                      SharedMemoryHandleVector 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;
+  virtual void Process(int pending_data, int index) OVERRIDE;
 
  private:
   AudioRendererSink::RenderCallback* render_callback_;
   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),
       callback_(NULL),
       ipc_(ipc),
       stream_id_(0),
       state_(IDLE),
       play_on_start_(true),
+      audio_thread_(false),
       stopping_hack_(false) {
   CHECK(ipc_);
 }
 
 void AudioOutputDevice::Initialize(const AudioParameters& params,
                                    RenderCallback* callback) {
   DCHECK(!callback_) << "Calling Initialize() twice?";
   DCHECK(params.IsValid());
   audio_parameters_ = params;
   callback_ = callback;
@@ skipping 158 matching lines @@
   // owners (WebRtcAudioDeviceImpl, AudioRendererImpl, etc...) can Stop() and
   // delete as they see fit. AudioOutputDevice should internally use WeakPtr
   // to handle teardown and thread hopping. See http://crbug.com/151051 for
   // details.
   base::AutoLock auto_lock(audio_thread_lock_);
   if (stopping_hack_)
     return;
 
   DCHECK(audio_thread_.IsStopped());
   audio_callback_.reset(new AudioOutputDevice::AudioThreadCallback(
-      audio_parameters_, handle, length, callback_));
+      audio_parameters_,
+      AudioDeviceThread::Callback::SharedMemoryHandleVector(1, handle),
+      length, callback_));
   audio_thread_.Start(audio_callback_.get(), socket_handle,
       "AudioOutputDevice");
   state_ = PAUSED;
 
   // We handle the case where Play() and/or Pause() may have been called
   // multiple times before OnStreamCreated() gets called.
   if (play_on_start_)
     PlayOnIOThread();
 }
 
 void AudioOutputDevice::OnIPCClosed() {
   DCHECK(message_loop()->BelongsToCurrentThread());
   state_ = IPC_CLOSED;
   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,
-    base::SharedMemoryHandle memory,
+    SharedMemoryHandleVector memory,
     int memory_length,
     AudioRendererSink::RenderCallback* render_callback)
     : AudioDeviceThread::Callback(audio_parameters,
                                   memory,
                                   memory_length),
       render_callback_(render_callback) {
 }
 
 AudioOutputDevice::AudioThreadCallback::~AudioThreadCallback() {
 }
 
 void AudioOutputDevice::AudioThreadCallback::MapSharedMemory() {
-  shared_memory_.Map(TotalSharedMemorySizeInBytes(memory_length_));
+  DCHECK_EQ(shared_memory_.size(), 1u);
+  base::SharedMemory* shared_buffer = shared_memory_[0];
+  shared_buffer->Map(TotalSharedMemorySizeInBytes(memory_length_));
 
   // Calculate output and input memory size.
   int output_memory_size = AudioBus::CalculateMemorySize(audio_parameters_);
   int input_channels = audio_parameters_.input_channels();
   int frames = audio_parameters_.frames_per_buffer();
   int input_memory_size =
       AudioBus::CalculateMemorySize(input_channels, frames);
 
   int io_size = output_memory_size + input_memory_size;
 
   DCHECK_EQ(memory_length_, io_size);
 
   output_bus_ =
-      AudioBus::WrapMemory(audio_parameters_, shared_memory_.memory());
+      AudioBus::WrapMemory(audio_parameters_, shared_buffer->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;
+        static_cast<char*>(shared_buffer->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) {
+void AudioOutputDevice::AudioThreadCallback::Process(
+    int pending_data, int index) {
+  base::SharedMemory* shared_buffer = shared_memory_[0];
   if (pending_data == kPauseMark) {
-    memset(shared_memory_.memory(), 0, memory_length_);
-    SetActualDataSizeInBytes(&shared_memory_, memory_length_, 0);
+    memset(shared_buffer->memory(), 0, memory_length_);
+    SetActualDataSizeInBytes(shared_buffer, 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
@@ skipping 10 matching lines @@
     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_,
+      shared_buffer, memory_length_,
       num_frames * sizeof(*output_bus_->channel(0)) * output_bus_->channels());
 }
 
 }  // namespace media.