1
    2
    3
    4
    5
    6
    7
    8
    9
   10
   11
   12
   13
   14
   15
   16
   17
   18
   19
   20
   21
   22
   23
   24
   25
   26
   27
   28
   29
   30
   31
   32
   33
   34
   35
   36
   37
   38
   39
   40
   41
   42
   43
   44
   45
   46
   47
   48
   49
   50
   51
   52
   53
   54
   55
   56
   57
   58
   59
   60
   61
   62
   63
   64
   65
   66
   67
   68
   69
   70
   71
   72
   73
   74
   75
   76
   77
   78
   79
   80
   81
   82
   83
   84
   85
   86
   87
   88
   89
   90
   91
   92
   93
   94
   95
   96


media / base / wall_clock_time_source.cc [blame]

// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "media/base/wall_clock_time_source.h"

#include "base/logging.h"

namespace media {

WallClockTimeSource::WallClockTimeSource()
    : tick_clock_(base::DefaultTickClock::GetInstance()) {}

WallClockTimeSource::WallClockTimeSource(const base::TickClock* tick_clock)
    : tick_clock_(tick_clock) {}

WallClockTimeSource::~WallClockTimeSource() = default;

void WallClockTimeSource::StartTicking() {
  DVLOG(1) << __func__;
  base::AutoLock auto_lock(lock_);
  DCHECK(!ticking_);
  ticking_ = true;
  reference_time_ = tick_clock_->NowTicks();
}

void WallClockTimeSource::StopTicking() {
  DVLOG(1) << __func__;
  base::AutoLock auto_lock(lock_);
  DCHECK(ticking_);
  base_timestamp_ = CurrentMediaTime_Locked();
  ticking_ = false;
  reference_time_ = tick_clock_->NowTicks();
}

void WallClockTimeSource::SetPlaybackRate(double playback_rate) {
  DVLOG(1) << __func__ << "(" << playback_rate << ")";
  base::AutoLock auto_lock(lock_);
  // Estimate current media time using old rate to use as a new base time for
  // the new rate.
  if (ticking_) {
    base_timestamp_ = CurrentMediaTime_Locked();
    reference_time_ = tick_clock_->NowTicks();
  }

  playback_rate_ = playback_rate;
}

void WallClockTimeSource::SetMediaTime(base::TimeDelta time) {
  DVLOG(1) << __func__ << "(" << time.InMicroseconds() << ")";
  base::AutoLock auto_lock(lock_);
  CHECK(!ticking_);
  base_timestamp_ = time;
  reference_time_ = base::TimeTicks();
}

base::TimeDelta WallClockTimeSource::CurrentMediaTime() {
  base::AutoLock auto_lock(lock_);
  return CurrentMediaTime_Locked();
}

bool WallClockTimeSource::GetWallClockTimes(
    const std::vector<base::TimeDelta>& media_timestamps,
    std::vector<base::TimeTicks>* wall_clock_times) {
  base::AutoLock auto_lock(lock_);
  DCHECK(wall_clock_times->empty());

  if (media_timestamps.empty()) {
    wall_clock_times->push_back(reference_time_);
  } else {
    // When playback is paused (rate is zero), assume a rate of 1.0.
    const double playback_rate = playback_rate_ ? playback_rate_ : 1.0;

    wall_clock_times->reserve(media_timestamps.size());
    for (const auto& media_timestamp : media_timestamps) {
      wall_clock_times->push_back(reference_time_ +
                                  (media_timestamp - base_timestamp_) /
                                      playback_rate);
    }
  }

  return playback_rate_ && ticking_;
}

base::TimeDelta WallClockTimeSource::CurrentMediaTime_Locked() {
  lock_.AssertAcquired();
  if (!ticking_ || !playback_rate_)
    return base_timestamp_;

  base::TimeTicks now = tick_clock_->NowTicks();
  return base_timestamp_ +
         base::Microseconds((now - reference_time_).InMicroseconds() *
                            playback_rate_);
}

}  // namespace media