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      1 // Copyright 2013 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef CONTENT_PUBLIC_RENDERER_MEDIA_STREAM_VIDEO_SINK_H_
      6 #define CONTENT_PUBLIC_RENDERER_MEDIA_STREAM_VIDEO_SINK_H_
      7 
      8 #include "base/callback.h"
      9 #include "base/compiler_specific.h"
     10 #include "base/memory/ref_counted.h"
     11 #include "base/time/time.h"
     12 #include "content/common/content_export.h"
     13 #include "content/public/renderer/media_stream_sink.h"
     14 
     15 namespace media {
     16 class VideoCaptureFormat;
     17 class VideoFrame;
     18 }
     19 
     20 namespace blink {
     21 class WebMediaStreamTrack;
     22 }
     23 
     24 namespace content {
     25 
     26 // This callback is used to deliver video frames.
     27 // |estimated_capture_time| - An optional field to provide the capture time of
     28 // the delivered video frame. This field usually means the local time when the
     29 // video frame was generated. It is possible for this value to be null if this
     30 // timing information cannot be determined. There is no gurantee that this
     31 // value is accurate. For example video frames from a remote source can only
     32 // provide this timing information as an estimate.
     33 // |video_frame->timestamp()| gives the presentation timestamp of the video
     34 // frame relative to the first frame generated by the corresponding source.
     35 // Because a source can start generating frames before a subscriber is added,
     36 // the first video frame delivered may not have timestamp equal to 0.
     37 typedef base::Callback<
     38   void(const scoped_refptr<media::VideoFrame>& video_frame,
     39        const media::VideoCaptureFormat& format,
     40        const base::TimeTicks& estimated_capture_time)>
     41     VideoCaptureDeliverFrameCB;
     42 
     43 // MediaStreamVideoSink is an interface used for receiving video frames from a
     44 // Video Stream Track or a Video Source.
     45 // http://dev.w3.org/2011/webrtc/editor/getusermedia.html
     46 // All methods calls will be done from the main render thread.
     47 class CONTENT_EXPORT MediaStreamVideoSink : public MediaStreamSink {
     48  public:
     49   // An implementation of MediaStreamVideoSink should call AddToVideoTrack when
     50   // it is ready to receive data from a video track. Before the implementation
     51   // is destroyed, RemoveFromVideoTrack must be called.
     52   //
     53   // Calls to these methods must be done on the main render thread.
     54   // Note that |callback| for frame delivery happens on the IO thread.
     55   //
     56   // Calling RemoveFromVideoTrack also not stop frame delivery through the
     57   // callback immediately because it may happen on another thread.
     58   // The added callback will be reset on the render thread.
     59   static void AddToVideoTrack(MediaStreamVideoSink* sink,
     60                               const VideoCaptureDeliverFrameCB& callback,
     61                               const blink::WebMediaStreamTrack& track);
     62   static void RemoveFromVideoTrack(MediaStreamVideoSink* sink,
     63                                    const blink::WebMediaStreamTrack& track);
     64 
     65  protected:
     66   virtual ~MediaStreamVideoSink() {}
     67 };
     68 
     69 
     70 }  // namespace content
     71 
     72 #endif  // CONTENT_PUBLIC_RENDERER_MEDIA_STREAM_VIDEO_SINK_H_
     73