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 #include "base/time/default_tick_clock.h"
   9
  10 namespace media {
  11
  12 WallClockTimeSource::WallClockTimeSource()
  13     : tick_clock_(new base::DefaultTickClock()),
  14       ticking_(false),
  15       playback_rate_(1.0f) {
  16 }
  17
  18 WallClockTimeSource::~WallClockTimeSource() {
  19 }
  20
  21 void WallClockTimeSource::StartTicking() {
  22   DVLOG(1) << __FUNCTION__;
  23   base::AutoLock auto_lock(lock_);
  24   DCHECK(!ticking_);
  25   ticking_ = true;
  26   reference_wall_ticks_ = tick_clock_->NowTicks();
  27 }
  28
  29 void WallClockTimeSource::StopTicking() {
  30   DVLOG(1) << __FUNCTION__;
  31   base::AutoLock auto_lock(lock_);
  32   DCHECK(ticking_);
  33   base_time_ = CurrentMediaTime_Locked();
  34   ticking_ = false;
  35   reference_wall_ticks_ = tick_clock_->NowTicks();
  36 }
  37
  38 void WallClockTimeSource::SetPlaybackRate(float playback_rate) {
  39   DVLOG(1) << __FUNCTION__ << "(" << playback_rate << ")";
  40   base::AutoLock auto_lock(lock_);
  41   // Estimate current media time using old rate to use as a new base time for
  42   // the new rate.
  43   if (ticking_) {
  44     base_time_ = CurrentMediaTime_Locked();
  45     reference_wall_ticks_ = tick_clock_->NowTicks();
  46   }
  47
  48   playback_rate_ = playback_rate;
  49 }
  50
  51 void WallClockTimeSource::SetMediaTime(base::TimeDelta time) {
  52   DVLOG(1) << __FUNCTION__ << "(" << time.InMicroseconds() << ")";
  53   base::AutoLock auto_lock(lock_);
  54   CHECK(!ticking_);
  55   base_time_ = time;
  56 }
  57
  58 base::TimeDelta WallClockTimeSource::CurrentMediaTime() {
  59   base::AutoLock auto_lock(lock_);
  60   return CurrentMediaTime_Locked();
  61 }
  62
  63 base::TimeTicks WallClockTimeSource::GetWallClockTime(base::TimeDelta time) {
  64   base::AutoLock auto_lock(lock_);
  65   if (!ticking_ || playback_rate_ == 0.0)
  66     return base::TimeTicks();
  67
  68   // See notes about |time| values less than |base_time_| in TimeSource header.
  69   return reference_wall_ticks_ +
  70          base::TimeDelta::FromMicroseconds(
  71              (time - base_time_).InMicroseconds() / playback_rate_);
  72 }
  73
  74 void WallClockTimeSource::SetTickClockForTesting(
  75     scoped_ptr<base::TickClock> tick_clock) {
  76   tick_clock_.swap(tick_clock);
  77 }
  78
  79 base::TimeDelta WallClockTimeSource::CurrentMediaTime_Locked() {
  80   lock_.AssertAcquired();
  81   if (!ticking_ || playback_rate_ == 0.0)
  82     return base_time_;
  83
  84   base::TimeTicks now = tick_clock_->NowTicks();
  85   return base_time_ +
  86          base::TimeDelta::FromMicroseconds(
  87              (now - reference_wall_ticks_).InMicroseconds() * playback_rate_);
  88 }
  89
  90 }  // namespace media