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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 #include "media/filters/video_frame_scheduler_impl.h"
      6 
      7 #include <list>
      8 
      9 #include "base/single_thread_task_runner.h"
     10 #include "base/time/default_tick_clock.h"
     11 #include "media/base/video_frame.h"
     12 
     13 namespace media {
     14 
     15 VideoFrameSchedulerImpl::VideoFrameSchedulerImpl(
     16     const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
     17     const DisplayCB& display_cb)
     18     : task_runner_(task_runner),
     19       display_cb_(display_cb),
     20       tick_clock_(new base::DefaultTickClock()) {
     21 }
     22 
     23 VideoFrameSchedulerImpl::~VideoFrameSchedulerImpl() {
     24 }
     25 
     26 void VideoFrameSchedulerImpl::ScheduleVideoFrame(
     27     const scoped_refptr<VideoFrame>& frame,
     28     base::TimeTicks wall_ticks,
     29     const DoneCB& done_cb) {
     30   DCHECK(task_runner_->BelongsToCurrentThread());
     31   DCHECK(!frame->end_of_stream());
     32   pending_frames_.push(PendingFrame(frame, wall_ticks, done_cb));
     33   ResetTimerIfNecessary();
     34 }
     35 
     36 void VideoFrameSchedulerImpl::Reset() {
     37   pending_frames_ = PendingFrameQueue();
     38   timer_.Stop();
     39 }
     40 
     41 void VideoFrameSchedulerImpl::SetTickClockForTesting(
     42     scoped_ptr<base::TickClock> tick_clock) {
     43   tick_clock_.swap(tick_clock);
     44 }
     45 
     46 void VideoFrameSchedulerImpl::ResetTimerIfNecessary() {
     47   if (pending_frames_.empty()) {
     48     DCHECK(!timer_.IsRunning());
     49     return;
     50   }
     51 
     52   // Negative times will schedule the callback to run immediately.
     53   timer_.Stop();
     54   timer_.Start(FROM_HERE,
     55                pending_frames_.top().wall_ticks - tick_clock_->NowTicks(),
     56                base::Bind(&VideoFrameSchedulerImpl::OnTimerFired,
     57                           base::Unretained(this)));
     58 }
     59 
     60 void VideoFrameSchedulerImpl::OnTimerFired() {
     61   base::TimeTicks now = tick_clock_->NowTicks();
     62 
     63   // Move all frames that have reached their deadline into a separate queue.
     64   std::list<PendingFrame> expired_frames;
     65   while (!pending_frames_.empty() && pending_frames_.top().wall_ticks <= now) {
     66     expired_frames.push_back(pending_frames_.top());
     67     pending_frames_.pop();
     68   }
     69 
     70   // Signal that all frames except for the last one as dropped.
     71   while (expired_frames.size() > 1) {
     72     expired_frames.front().done_cb.Run(expired_frames.front().frame, DROPPED);
     73     expired_frames.pop_front();
     74   }
     75 
     76   // Display the last expired frame.
     77   if (!expired_frames.empty()) {
     78     display_cb_.Run(expired_frames.front().frame);
     79     expired_frames.front().done_cb.Run(expired_frames.front().frame, DISPLAYED);
     80     expired_frames.pop_front();
     81   }
     82 
     83   ResetTimerIfNecessary();
     84 }
     85 
     86 VideoFrameSchedulerImpl::PendingFrame::PendingFrame(
     87     const scoped_refptr<VideoFrame>& frame,
     88     base::TimeTicks wall_ticks,
     89     const DoneCB& done_cb)
     90     : frame(frame), wall_ticks(wall_ticks), done_cb(done_cb) {
     91 }
     92 
     93 VideoFrameSchedulerImpl::PendingFrame::~PendingFrame() {
     94 }
     95 
     96 bool VideoFrameSchedulerImpl::PendingFrame::operator<(
     97     const PendingFrame& other) const {
     98   // Flip the comparison as std::priority_queue<T>::top() returns the largest
     99   // element.
    100   //
    101   // Assume video frames with identical timestamps contain identical content.
    102   return wall_ticks > other.wall_ticks;
    103 }
    104 
    105 }  // namespace media
    106