Implement renderer AudioDevice API for low-latency audio output...

chrome/renderer/audio_device.h

+// Copyright (c) 2010 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.
+
+#ifndef CHROME_RENDERER_AUDIO_DEVICE_H_
+#define CHROME_RENDERER_AUDIO_DEVICE_H_
+#pragma once
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/scoped_ptr.h"
+#include "base/shared_memory.h"
+#include "base/threading/simple_thread.h"
+#include "chrome/common/render_messages.h"
+#include "chrome/renderer/audio_message_filter.h"
+
+// Each instance of AudioDevice corresponds to one host stream.
+// This class is not thread-safe, so its methods must be called from
+// the same thread.
+class AudioDevice : public AudioMessageFilter::Delegate,
+                    public base::DelegateSimpleThread::Delegate {
+ public:
+  class RenderCallback {
+   public:
+    virtual void Render(const std::vector<float*>& audio_data,
+                        size_t number_of_frames) = 0;
+   protected:
+    virtual ~RenderCallback() {}
+  };
+
+  // |buffer_size| is the number of sample-frames.
+  AudioDevice(size_t buffer_size,
+              int channels,
+              double sample_rate,
+              RenderCallback* callback);
+  virtual ~AudioDevice();
+
+  // Returns |true| on success.
+  bool Start();
+  bool Stop();
+
+ private:
+  // AudioMessageFilter::Delegate implementation.
+  virtual void OnRequestPacket(AudioBuffersState buffers_state);
+  virtual void OnStateChanged(const ViewMsg_AudioStreamState_Params& state);
+  virtual void OnCreated(base::SharedMemoryHandle handle, uint32 length);
+  virtual void OnLowLatencyCreated(base::SharedMemoryHandle handle,
+                                   base::SyncSocket::Handle socket_handle,
+                                   uint32 length);
+  virtual void OnVolume(double volume);
+  virtual void OnDestroy();
+
+  // DelegateSimpleThread::Delegate implementation.
+  virtual void Run();
+
+  // Format
+  size_t buffer_size_;  // in sample-frames
+  int channels_;
+  double sample_rate_;
+
+  // Calls the client's callback for rendering audio.
+  void FireRenderCallback();
+  RenderCallback* callback_;
+
+  // The client callback renders audio into here.
+  std::vector<float*> audio_data_;
+
+  // Callbacks for rendering audio occur on this thread.
+  scoped_ptr<base::DelegateSimpleThread> audio_thread_;
+
+  // IPC message stuff.
+  base::SharedMemory* shared_memory() { return shared_memory_.get(); }
+  base::SyncSocket* socket() { return socket_.get(); }
+  void* shared_memory_data() { return shared_memory()->memory(); }
+
+  static scoped_refptr<AudioMessageFilter> filter_;
+  int32 stream_id_;
+  scoped_ptr<base::SharedMemory> shared_memory_;
+  scoped_ptr<base::SyncSocket> socket_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioDevice);
+};
+
+#endif  // CHROME_RENDERER_AUDIO_DEVICE_H_