Integrate HTMLMediaElement with Web Audio API's MediaElementAudioSourceNode

content/renderer/render_audiosourceprovider.h

+// Copyright (c) 2011 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.
+//
+// RenderAudioSourceProvider provides a bridge between classes:
+//     WebKit::WebAudioSourceProvider <---> media::AudioRendererSink
+//
+// RenderAudioSourceProvider is a "sink" of audio, and uses a default
+// AudioDevice if a client has not explicitly been set.
+//
+// WebKit optionally sets a client, and then periodically calls provideInput()
+// to render a certain number of audio sample-frames.  provideInput()
+// uses the renderer to get this data, and then massages it into the form
+// required by provideInput().  In this case, the default AudioDevice
+// is no longer used.
+//
+// THREAD SAFETY:
+// It is assumed that the callers to setClient() and provideInput()
+// implement appropriate locking for thread safety when making
+// these calls.  This happens in WebKit.
+
+#ifndef CONTENT_RENDERER_RENDER_AUDIOSOURCEPROVIDER_H_
+#define CONTENT_RENDERER_RENDER_AUDIOSOURCEPROVIDER_H_
+
+#include <vector>
+
+#include "content/renderer/media/audio_device.h"
+#include "media/base/audio_renderer_sink.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebVector.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebAudioSourceProvider.h"
+
+namespace WebKit {
+class WebAudioSourceProviderClient;
+}
+
+class RenderAudioSourceProvider
+    : public WebKit::WebAudioSourceProvider,
+      public media::AudioRendererSink {
+ public:
+  RenderAudioSourceProvider();
+  virtual ~RenderAudioSourceProvider();
+
+  // WebKit::WebAudioSourceProvider implementation.
+
+  // WebKit calls setClient() if it desires to take control of the rendered
+  // audio stream.  We call client's setFormat() when the audio stream format
+  // is known.
+  virtual void setClient(WebKit::WebAudioSourceProviderClient* client);
+
+  // If setClient() has been called, then WebKit calls provideInput()
+  // periodically to get the rendered audio stream.
+  virtual void provideInput(const WebKit::WebVector<float*>& audio_data,
+                            size_t number_of_frames);
+
+  // AudioRendererSink implementation.
+  virtual void Start() OVERRIDE;
+  virtual void Stop() OVERRIDE;
+  virtual void Play() OVERRIDE;
+  virtual void Pause(bool flush) OVERRIDE;
+  virtual bool SetVolume(double volume) OVERRIDE;
+  virtual void GetVolume(double* volume) OVERRIDE;
+  virtual void Initialize(size_t buffer_size,
+                          int channels,
+                          double sample_rate,
+                          AudioParameters::Format latency_format,
+                          RenderCallback* renderer) OVERRIDE;
+
+ private:
+  // Set to true when Initialize() is called.
+  bool is_initialized_;
+  int channels_;
+  double sample_rate_;
+
+  bool is_running_;
+  double volume_;
+  media::AudioRendererSink::RenderCallback* renderer_;
+  WebKit::WebAudioSourceProviderClient* client_;
+
+  // Protects access to sink_
+  base::Lock sink_lock_;
+
+  // default_sink_ is the default sink.
+  scoped_refptr<media::AudioRendererSink> default_sink_;
+
+  DISALLOW_COPY_AND_ASSIGN(RenderAudioSourceProvider);
+};
+
+#endif  // CONTENT_RENDERER_RENDER_AUDIOSOURCEPROVIDER_H_