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>
+
+#include "base/compiler_specific.h"
+#include "base/synchronization/lock.h"
+#include "content/common/content_export.h"
+#include "third_party/libjingle/source/talk/media/base/videocapturer.h"
+
+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,

[wjia(left Chromium), 2013/05/03 21:42:55]

const webkit::ppapi::PPB_ImageData_Impl& image_data ? It seems image_data will
not be modified inside PutFrame().

[Ronghua Wu (Left Chromium), 2013/05/03 22:40:02]

I can't actually. Before using the PPB_ImageData_Impl, I need to verify it with
ImageDataAutoMapper, which doesn't take a const pointer.

+                        int64 time_stamp_ns) = 0;
+  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
+    : 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.
+  // This method will be called by the Pepper host from render thread.
+  virtual void PutFrame(webkit::ppapi::PPB_ImageData_Impl* image_data,
+                        int64 time_stamp_ns) OVERRIDE;
+
+ private:
+  bool started_;
+  base::Lock lock_;

[wjia(left Chromium), 2013/05/03 21:42:55]

Please add comment on which is protected by this |lock_|.

[Ronghua Wu (Left Chromium), 2013/05/03 22:40:02]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(PpFrameWriter);
+};
+
+// VideoDestinationHandler is a glue class between the webrtc MediaStream and
+// the effects pepper plugin host.
+class CONTENT_EXPORT VideoDestinationHandler {
+ public:
+  // 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|.
+  // The caller of the function takes the ownership of |frame_writer|.
+  // Returns true on success and false on failure.

[wjia(left Chromium), 2013/05/03 21:42:55]

Could you add some comments on what are |factory| and |registry|? |registry|
could be NULL?

[Ronghua Wu (Left Chromium), 2013/05/03 22:40:02]

Added comments. And change the code a bit so that the factory can be null as
well. 

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

[wjia(left Chromium), 2013/05/03 21:42:55]

Is it possible to use frame_writer==NULL as indication of false? If so, you can
return FrameWriterInterface*, instead of bool.

[Ronghua Wu (Left Chromium), 2013/05/03 22:40:02]

I prefer to keep as it's to align with the other Open we have in the
video_source_handler.

+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(VideoDestinationHandler);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_MEDIA_VIDEO_DESTINATION_HANDLER_H_
+