Integrate HTMLMediaElement with Web Audio API's MediaElementAudioSourceNode

media/filters/audio_renderer_sink.h

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.

[acolwell GONE FROM CHROMIUM, 2011/12/21 22:53:56]

I think this should go in media/base so it is in the same directory that the
AudioRenderer interface is declared.

[Chris Rogers, 2011/12/22 00:54:33]

Done.

+// 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

[acolwell GONE FROM CHROMIUM, 2011/12/21 22:53:56]

Remove "in the renderer process". media is techincally independent of the Chrome
process model. The last sentence should also be removed since this code can
operate independent of the Chrome process model.

[Chris Rogers, 2011/12/22 00:54:33]

Done.

+// periodically call Render() on a callback object.  The normal implementation
+// 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 {

[acolwell GONE FROM CHROMIUM, 2011/12/21 22:53:56]

Please convert this to 
typedef base::Callback<void(const std::vector<float*>&, size_t, size_t)>
RenderCallback; 

so it matches the callback pattern used in the rest of the media code.

[Chris Rogers, 2011/12/22 00:54:33]

I think it would be better to defer this change to a followup CL because it
brings several more files and changes into this CL (the current clients of
AudioDevice) with associated risk.  The current pattern is effectively identical
to what has been in AudioDevice for quite some time.  So the proposed change
seems orthogonal to the rest of the changes in this patch.  I don't disagree
with your proposal, just the staging of the change.  How about a TODO here? 

On 2011/12/21 22:53:56, acolwell wrote:

+   public:
+    virtual void 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;

[acolwell GONE FROM CHROMIUM, 2011/12/21 22:53:56]

Change to const RenderCallback&.

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