media/base/wall_clock_time_source.cc

   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/base/wall_clock_time_source.h"
   6
   7 #include "base/logging.h"
   8
   9 namespace media {
  10
  11 WallClockTimeSource::WallClockTimeSource()
  12     : tick_clock_(&default_tick_clock_), ticking_(false), playback_rate_(1.0) {
  13 }
  14
  15 WallClockTimeSource::~WallClockTimeSource() {
  16 }
  17
  18 void WallClockTimeSource::StartTicking() {
  19   DVLOG(1) << __FUNCTION__;
  20   base::AutoLock auto_lock(lock_);
  21   DCHECK(!ticking_);
  22   ticking_ = true;
  23   reference_time_ = tick_clock_->NowTicks();
  24 }
  25
  26 void WallClockTimeSource::StopTicking() {
  27   DVLOG(1) << __FUNCTION__;
  28   base::AutoLock auto_lock(lock_);
  29   DCHECK(ticking_);
  30   base_timestamp_ = CurrentMediaTime_Locked();
  31   ticking_ = false;
  32   reference_time_ = tick_clock_->NowTicks();
  33 }
  34
  35 void WallClockTimeSource::SetPlaybackRate(double playback_rate) {
  36   DVLOG(1) << __FUNCTION__ << "(" << playback_rate << ")";
  37   base::AutoLock auto_lock(lock_);
  38   // Estimate current media time using old rate to use as a new base time for
  39   // the new rate.
  40   if (ticking_) {
  41     base_timestamp_ = CurrentMediaTime_Locked();
  42     reference_time_ = tick_clock_->NowTicks();
  43   }
  44
  45   playback_rate_ = playback_rate;
  46 }
  47
  48 void WallClockTimeSource::SetMediaTime(base::TimeDelta time) {
  49   DVLOG(1) << __FUNCTION__ << "(" << time.InMicroseconds() << ")";
  50   base::AutoLock auto_lock(lock_);
  51   CHECK(!ticking_);
  52   base_timestamp_ = time;
  53 }
  54
  55 base::TimeDelta WallClockTimeSource::CurrentMediaTime() {
  56   base::AutoLock auto_lock(lock_);
  57   return CurrentMediaTime_Locked();
  58 }
  59
  60 bool WallClockTimeSource::GetWallClockTimes(
  61     const std::vector<base::TimeDelta>& media_timestamps,
  62     std::vector<base::TimeTicks>* wall_clock_times) {
  63   base::AutoLock auto_lock(lock_);
  64   DCHECK(wall_clock_times->empty());
  65
  66   if (media_timestamps.empty()) {
  67     wall_clock_times->push_back(reference_time_);
  68   } else {
  69     // When playback is paused (rate is zero), assume a rate of 1.0.
  70     const double playback_rate = playback_rate_ ? playback_rate_ : 1.0;
  71
  72     wall_clock_times->reserve(media_timestamps.size());
  73     for (const auto& media_timestamp : media_timestamps) {
  74       wall_clock_times->push_back(reference_time_ +
  75                                   (media_timestamp - base_timestamp_) /
  76                                       playback_rate);
  77     }
  78   }
  79
  80   return playback_rate_ && ticking_;
  81 }
  82
  83 base::TimeDelta WallClockTimeSource::CurrentMediaTime_Locked() {
  84   lock_.AssertAcquired();
  85   if (!ticking_ || !playback_rate_)
  86     return base_timestamp_;
  87
  88   base::TimeTicks now = tick_clock_->NowTicks();
  89   return base_timestamp_ +
  90          base::TimeDelta::FromMicroseconds(
  91              (now - reference_time_).InMicroseconds() * playback_rate_);
  92 }
  93
  94 }  // namespace media