Integrate HTMLMediaElement with Web Audio API's MediaElementAudioSourceNode

media/filters/audio_renderer_sink.h

Index: media/filters/audio_renderer_sink.h
===================================================================
--- media/filters/audio_renderer_sink.h	(revision 0)
+++ media/filters/audio_renderer_sink.h	(revision 0)
@@ -0,0 +1,66 @@
+// 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_FILTERS_AUDIO_RENDERER_SINK_H_
+#define MEDIA_FILTERS_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 in the renderer process.  An implementation is expected to
+// periodically call Render() on a callback object.  The normal implementation

[henrika (OOO until Aug 14), 2011/12/19 14:27:05]

And a non-normal implementation would do what ;-)

[Chris Rogers, 2011/12/19 21:40:35]

RenderAudioSourceProvider is an example in this CL of a "non-normal"
implementation.  So the abstraction we're making here isn't just an intellectual
exercise.  But, your point is well taken that the language "normal
implementation" is a bit awkward.  Any suggestions for how I could reword this
comment?

On 2011/12/19 14:27:05, henrika wrote:

[henrika (OOO until Aug 14), 2011/12/20 21:01:01]

typical instead of normal?

+// will talk with the browser process to get a rendered audio stream to the
+// audio hardware.
+
+class AudioRendererSink
+    : public base::RefCountedThreadSafe<media::AudioRendererSink> {
+ public:
+  class RenderCallback {
+   public:
+    virtual void Render(const std::vector<float*>& audio_data,
+                        size_t number_of_frames,
+                        size_t audio_delay_milliseconds) = 0;
+
+    virtual void SetAudioRendererSink(media::AudioRendererSink* audio_sink) { }

[henrika (OOO until Aug 14), 2011/12/19 14:27:05]

What about adding a comment on this method?

[Chris Rogers, 2011/12/19 21:40:35]

Tommi had a similar comment about this method in audio_renderer_impl.h

There I responded that maybe it's best to simplify this and remove this method
from the abstract interface here, since it's not that generally useful.  And
instead just have it be a method specific to AudioRendererImpl.

What do you think?
On 2011/12/19 14:27:05, henrika wrote:

[henrika (OOO until Aug 14), 2011/12/20 21:01:01]

Seems like you did changes here already. No further comments here.

+
+   protected:
+    virtual ~RenderCallback() { }

[tommi (sloooow) - chröme, 2011/12/19 15:26:24]

{}

[Chris Rogers, 2011/12/19 21:40:35]

Done.

+  };
+
+  virtual ~AudioRendererSink() { }

[tommi (sloooow) - chröme, 2011/12/19 15:26:24]

{}

[Chris Rogers, 2011/12/19 21:40:35]

Done.

+
+  // Initialize() sets important information about the audio stream format.

[henrika (OOO until Aug 14), 2011/12/19 14:27:05]

nit, don't think we have to list the function name in the comment as well.

[Chris Rogers, 2011/12/19 21:40:35]

Done.

+  // 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;
+};
+
+}  // namespace media
+
+#endif  // MEDIA_FILTERS_AUDIO_RENDERER_SINK_H_