media/filters/video_frame_scheduler.h

   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_