media/filters/video_frame_scheduler.h

// Copyright 2014 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 MEDIA_FILTERS_VIDEO_FRAME_SCHEDULER_H_
#define MEDIA_FILTERS_VIDEO_FRAME_SCHEDULER_H_

#include "base/callback.h"
#include "base/memory/ref_counted.h"
#include "base/time/time.h"
#include "media/base/media_export.h"

namespace media {

class VideoFrame;

// Defines an abstract video frame scheduler that is capable of managing the
// display of video frames at explicit times.
class MEDIA_EXPORT VideoFrameScheduler {
 public:
  VideoFrameScheduler() {}
  virtual ~VideoFrameScheduler() {}

  enum Reason {
    DISPLAYED,  // Frame was displayed.
    DROPPED,    // Frame was dropped.
  };
  typedef base::Callback<void(const scoped_refptr<VideoFrame>&, Reason)> DoneCB;

  // Schedule |frame| to be displayed at |wall_ticks|, firing |done_cb| when
  // the scheduler has finished with the frame.
  //
  // To avoid reentrancy issues, |done_cb| is run on a separate calling stack.
  virtual void ScheduleVideoFrame(const scoped_refptr<VideoFrame>& frame,
                                  base::TimeTicks wall_ticks,
                                  const DoneCB& done_cb) = 0;

  // Causes the scheduler to cancel any previously scheduled frames.
  //
  // There is no guarantee that |done_cb|'s for previously scheduled frames
  // will not be run. Clients should implement callback tracking/cancellation
  // if they are sensitive to old callbacks being run.
  virtual void Reset() = 0;
};

}  // namespace media

#endif  // MEDIA_FILTERS_VIDEO_FRAME_SCHEDULER_H_