Integrate HTMLMediaElement with Web Audio API's MediaElementAudioSourceNode

media/base/audio_renderer_sink.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.
+
+#ifndef MEDIA_BASE_AUDIO_RENDERER_SINK_H_
+#define MEDIA_BASE_AUDIO_RENDERER_SINK_H_
+
+#include <vector>
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "media/audio/audio_parameters.h"
+
+namespace media {
+
+// AudioRendererSink is an interface representing the end-point for
+// rendered audio.  An implementation is expected to
+// periodically call Render() on a callback object.
+
+class AudioRendererSink
+    : public base::RefCountedThreadSafe<media::AudioRendererSink> {
+ public:
+  class RenderCallback {
+   public:
+    // Fills entire buffer of length |number_of_frames| but returns actual
+    // number of frames it got from its source (|number_of_frames| in case of
+    // continuous stream). That actual number of frames is passed to host
+    // together with PCM audio data and host is free to use or ignore it.
+    // TODO(crogers): use base:Callback instead.
+    virtual size_t Render(const std::vector<float*>& audio_data,
+                          size_t number_of_frames,
+                          size_t audio_delay_milliseconds) = 0;
+
+   protected:
+    virtual ~RenderCallback() {}
+  };
+
+  virtual ~AudioRendererSink() {}
+
+  // Sets important information about the audio stream format.
+  // It must be called before any of the other methods.
+  virtual void Initialize(size_t buffer_size,
+                          int channels,
+                          double sample_rate,
+                          AudioParameters::Format latency_format,
+                          RenderCallback* callback) = 0;
+
+  // Starts audio playback.
+  virtual void Start() = 0;
+
+  // Stops audio playback.
+  virtual void Stop() = 0;
+
+  // Pauses playback.
+  virtual void Pause(bool flush) = 0;
+
+  // Resumes playback after calling Pause().
+  virtual void Play() = 0;
+
+  // Sets the playback volume, with range [0.0, 1.0] inclusive.
+  // Returns |true| on success.
+  virtual bool SetVolume(double volume) = 0;
+
+  // Gets the playback volume, with range [0.0, 1.0] inclusive.
+  virtual void GetVolume(double* volume) = 0;
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_AUDIO_RENDERER_SINK_H_