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      1 // Copyright 2014 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 MEDIA_FILTERS_VIDEO_FRAME_SCHEDULER_H_
      6 #define MEDIA_FILTERS_VIDEO_FRAME_SCHEDULER_H_
      7 
      8 #include "base/callback.h"
      9 #include "base/memory/ref_counted.h"
     10 #include "base/time/time.h"
     11 #include "media/base/media_export.h"
     12 
     13 namespace media {
     14 
     15 class VideoFrame;
     16 
     17 // Defines an abstract video frame scheduler that is capable of managing the
     18 // display of video frames at explicit times.
     19 class MEDIA_EXPORT VideoFrameScheduler {
     20  public:
     21   VideoFrameScheduler() {}
     22   virtual ~VideoFrameScheduler() {}
     23 
     24   enum Reason {
     25     DISPLAYED,  // Frame was displayed.
     26     DROPPED,    // Frame was dropped.
     27   };
     28   typedef base::Callback<void(const scoped_refptr<VideoFrame>&, Reason)> DoneCB;
     29 
     30   // Schedule |frame| to be displayed at |wall_ticks|, firing |done_cb| when
     31   // the scheduler has finished with the frame.
     32   //
     33   // To avoid reentrancy issues, |done_cb| is run on a separate calling stack.
     34   virtual void ScheduleVideoFrame(const scoped_refptr<VideoFrame>& frame,
     35                                   base::TimeTicks wall_ticks,
     36                                   const DoneCB& done_cb) = 0;
     37 
     38   // Causes the scheduler to cancel any previously scheduled frames.
     39   //
     40   // There is no guarantee that |done_cb|'s for previously scheduled frames
     41   // will not be run. Clients should implement callback tracking/cancellation
     42   // if they are sensitive to old callbacks being run.
     43   virtual void Reset() = 0;
     44 };
     45 
     46 }  // namespace media
     47 
     48 #endif  // MEDIA_FILTERS_VIDEO_FRAME_SCHEDULER_H_
     49