Chrome MediaStream VideoTrack implementation.

content/renderer/media/media_stream_video_track.h

 // Copyright 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_MEDIA_STREAM_VIDEO_TRACK_H_
 #define CONTENT_RENDERER_MEDIA_MEDIA_STREAM_VIDEO_TRACK_H_
 
+#include <vector>
+
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_vector.h"
 #include "base/threading/thread_checker.h"
 #include "content/common/content_export.h"
 #include "content/public/renderer/media_stream_video_sink.h"
 #include "content/renderer/media/media_stream_track.h"
+#include "content/renderer/media/media_stream_video_source.h"
 
 namespace webrtc {
 class VideoTrackInterface;
 }
 
 namespace content {
 
 class MediaStreamDependencyFactory;
 class WebRtcVideoSinkAdapter;
 
 // MediaStreamVideoTrack is a video specific representation of a
 // blink::WebMediaStreamTrack in content. It is owned by the blink object
 // and can be retrieved from a blink object using
-// WebMediaStreamTrack::extraData()
+// WebMediaStreamTrack::extraData() or MediaStreamVideoTrack::GetVideoTrack.
 class CONTENT_EXPORT MediaStreamVideoTrack : public MediaStreamTrack {
  public:
+  // Help method to create a blink::WebMediaStreamTrack and a
+  // MediaStreamVideoTrack instance. The MediaStreamVideoTrack object is owned
+  // by the blink object in its WebMediaStreamTrack::ExtraData member.
+  // |callback| is triggered if the track is added to the source
+  // successfully and will receive video frames that match |constraints|
+  // or if the source fail to provide video frames.
+  // If |enabled| is true, sinks added to the track will
+  // receive video frames when the source deliver frames to the track.
+  static blink::WebMediaStreamTrack CreateVideoTrack(
+      MediaStreamVideoSource* source,
+      const blink::WebMediaConstraints& constraints,
+      const MediaStreamVideoSource::ConstraintsCallback& callback,
+      bool enabled,
+      MediaStreamDependencyFactory* factory);
+
+  static MediaStreamVideoTrack* GetVideoTrack(
+      const blink::WebMediaStreamTrack& track);
+
   // Constructor for local video tracks.
-  explicit MediaStreamVideoTrack(MediaStreamDependencyFactory* factory);
-  // Constructor for remote video tracks.
-  explicit MediaStreamVideoTrack(webrtc::VideoTrackInterface* track);
+   MediaStreamVideoTrack(
+       MediaStreamVideoSource* source,
+       const blink::WebMediaConstraints& constraints,
+       const MediaStreamVideoSource::ConstraintsCallback& callback,
+       bool enabled,
+       MediaStreamDependencyFactory* factory);
   virtual ~MediaStreamVideoTrack();
-  void AddSink(MediaStreamVideoSink* sink);
-  void RemoveSink(MediaStreamVideoSink* sink);
+  virtual void AddSink(MediaStreamVideoSink* sink);
+  virtual void RemoveSink(MediaStreamVideoSink* sink);
 
   virtual webrtc::VideoTrackInterface* GetVideoAdapter() OVERRIDE;
+  virtual void SetEnabled(bool enabled) OVERRIDE;
+
+  void OnVideoFrame(const scoped_refptr<media::VideoFrame>& frame);
+  void OnReadyStateChanged(blink::WebMediaStreamSource::ReadyState state);
+
+ protected:
+  // Used to DCHECK that we are called on the correct thread.
+  base::ThreadChecker thread_checker_;
 
  private:
-  // Used to DCHECK that we are called on the correct thread.
-  base::ThreadChecker thread_checker_;
-  ScopedVector<WebRtcVideoSinkAdapter> sinks_;
+  bool enabled_;
+  std::vector<MediaStreamVideoSink*> sinks_;
+
+  // Weak ref to the source this tracks is connected to.  |source_| is owned
+  // by the blink::WebMediaStreamSource and is guaranteed to outlive the
+  // track.
+  MediaStreamVideoSource* source_;
 
   // Weak ref to a MediaStreamDependencyFactory, owned by the RenderThread.
   // It's valid for the lifetime of RenderThread.
   MediaStreamDependencyFactory* factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaStreamVideoTrack);
 };
 
+// WebRtcMediaStreamVideoTrack is a Chrome representation of a video track.

[Ronghua Wu (Left Chromium), 2014/03/04 01:04:11]

MediaStreamVideoTrack is 'a representation in content'. And this one is 'a
Chrome representation'. I can't tell the different from the comment.

[perkj_chrome, 2014/03/04 10:44:51]

ok- sticking to content.

[Ronghua Wu (Left Chromium), 2014/03/04 23:50:55]

I was more of hoping you can explain what is the different between
WebRtcMediaStreamVideoTrack and MediaStreamVideoTrack

+// received on a PeerConnection.
+// TODO(perkj): Replace WebRtcMediaStreamVideoTrack with a remote
+// MediaStreamVideoSource class so that all tracks are MediaStreamVideoTracks
+// and new tracks can be cloned from the original remote video track.
+class CONTENT_EXPORT WebRtcMediaStreamVideoTrack
+    : public MediaStreamVideoTrack {
+ public:
+  explicit WebRtcMediaStreamVideoTrack(webrtc::VideoTrackInterface* track);
+  virtual ~WebRtcMediaStreamVideoTrack();
+  virtual void AddSink(MediaStreamVideoSink* sink) OVERRIDE;
+  virtual void RemoveSink(MediaStreamVideoSink* sink) OVERRIDE;
+
+ private:
+  ScopedVector<WebRtcVideoSinkAdapter> sinks_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebRtcMediaStreamVideoTrack);
+};
+
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_MEDIA_STREAM_VIDEO_TRACK_H_