Effects Pepper Plugin and MediaStream Glue.

content/renderer/media/video_destination_handler.h

+// Copyright (c) 2013 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 CONTENT_RENDERER_MEDIA_VIDEO_DESTINATION_HANDLER_H_
+#define CONTENT_RENDERER_MEDIA_VIDEO_DESTINATION_HANDLER_H_
+
+#include <string>
+#include <vector>

[wjia(left Chromium), 2013/05/03 02:00:38]

not needed since vector is used as part of API in cricket::VideoCapturer.

[Ronghua Wu (Left Chromium), 2013/05/03 05:37:28]

True. But somehow lint is not happy if I don't include vector. So I will keep it
anyway.

+
+#include "base/compiler_specific.h"
+#include "content/common/content_export.h"
+#include "third_party/libjingle/source/talk/media/base/videocapturer.h"
+#include "third_party/WebKit/Source/Platform/chromium/public/WebMediaStream.h"

[wjia(left Chromium), 2013/05/03 02:00:38]

not used?

[Ronghua Wu (Left Chromium), 2013/05/03 05:37:28]

Done.

+
+namespace webkit {
+namespace ppapi {
+class PPB_ImageData_Impl;
+}
+}
+
+namespace content {
+
+class MediaStreamDependencyFactory;
+class MediaStreamRegistryInterface;
+
+// Interface used by the effects pepper plugin to output the processed frame
+// to the video track.
+class CONTENT_EXPORT FrameWriterInterface {
+ public:
+  // The ownership of the |image_data| deosn't transfer. So the implementation
+  // of this interface should make a copy of the |image_data| before return.
+  virtual void PutFrame(webkit::ppapi::PPB_ImageData_Impl* image_data,
+                        int64 time_stamp_ns) = 0;
+
+ protected:
+  virtual ~FrameWriterInterface() {}
+};
+
+// PpFrameWriter implements cricket::VideoCapturer so that it can be used in
+// the native video track's video source. It also implements
+// FrameWriterInterface, which will be used by the effects pepper plugin to
+// inject the processed frame.
+class CONTENT_EXPORT PpFrameWriter

[wjia(left Chromium), 2013/05/03 02:00:38]

How is lifetime of PpFrameWriter managed? It will be accessed from both
libjingle and Pepper. How to guarantee it won't be used after free?

[Ronghua Wu (Left Chromium), 2013/05/03 05:37:28]

Good question. The PpFrameWriter is owned by the mediatrack. What about let the
Pepper owns a reference to the mediatrack, then PpFrameWriter will always be
valid before the mediatrack is released.

Please see the PpFrameWriterProxy I added.

+    : public NON_EXPORTED_BASE(cricket::VideoCapturer),
+      public FrameWriterInterface {
+ public:
+  PpFrameWriter();
+  virtual ~PpFrameWriter();
+
+  // cricket::VideoCapturer implementation.
+  // These methods are accessed from a libJingle worker thread.
+  virtual cricket::CaptureState Start(
+      const cricket::VideoFormat& capture_format) OVERRIDE;
+  virtual void Stop() OVERRIDE;
+  virtual bool IsRunning() OVERRIDE;
+  virtual bool GetPreferredFourccs(std::vector<uint32>* fourccs) OVERRIDE;
+  virtual bool GetBestCaptureFormat(const cricket::VideoFormat& desired,
+                                    cricket::VideoFormat* best_format) OVERRIDE;
+  virtual bool IsScreencast() const OVERRIDE;
+
+  // FrameWriterInterface implementation.
+  virtual void PutFrame(webkit::ppapi::PPB_ImageData_Impl* image_data,
+                        int64 time_stamp_ns) OVERRIDE;
+
+ private:
+  bool started_;
+
+  DISALLOW_COPY_AND_ASSIGN(PpFrameWriter);
+};
+
+// VideoDestinationHandler is a glue class between the webrtc MediaStream and
+// the effects pepper plugin host.
+class CONTENT_EXPORT VideoDestinationHandler {

[wjia(left Chromium), 2013/05/03 02:00:38]

Will this class be expanded in the future? If not, how about making it a static
function inside PpFrameWriter, e.g.,

static Open(MediaStreamDependencyFactory* factory,
            MediaStreamRegistryInterface* registry,
            const std::string& url,
            FrameWriterInterface** frame_writer);

[Ronghua Wu (Left Chromium), 2013/05/03 05:37:28]

Didn't seem will be expanded from what I can tell. I think it's a good idea. 

+ public:
+  VideoDestinationHandler(MediaStreamDependencyFactory* factory,
+                          MediaStreamRegistryInterface* registry);
+  // Instantiates and adds a new video track to the MediaStream specified by
+  // |url|. Returns a handler for delivering frames to the new video track as
+  // |frame_writer|.
+  // Returns true on success and false on failure.
+  bool Open(const std::string& url, FrameWriterInterface** frame_writer);
+  virtual ~VideoDestinationHandler();
+
+ private:
+  MediaStreamDependencyFactory* factory_;
+  MediaStreamRegistryInterface* registry_;
+
+  DISALLOW_COPY_AND_ASSIGN(VideoDestinationHandler);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_MEDIA_VIDEO_DESTINATION_HANDLER_H_
+