media/base/clock.cc

   1 // Copyright (c) 2012 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/clock.h"
   6
   7 #include <algorithm>
   8
   9 #include "base/logging.h"
  10 #include "base/time/tick_clock.h"
  11 #include "media/base/buffers.h"
  12
  13 namespace media {
  14
  15 Clock::Clock(base::TickClock* clock) : clock_(clock) {
  16   DCHECK(clock_);
  17   Reset();
  18 }
  19
  20 Clock::~Clock() {}
  21
  22 bool Clock::IsPlaying() const {
  23   return playing_;
  24 }
  25
  26 base::TimeDelta Clock::Play() {
  27   DCHECK(!playing_);
  28   UpdateReferencePoints();
  29   playing_ = true;
  30   return media_time_;
  31 }
  32
  33 base::TimeDelta Clock::Pause() {
  34   DCHECK(playing_);
  35   UpdateReferencePoints();
  36   playing_ = false;
  37   return media_time_;
  38 }
  39
  40 void Clock::SetPlaybackRate(float playback_rate) {
  41   UpdateReferencePoints();
  42   playback_rate_ = playback_rate;
  43 }
  44
  45 void Clock::SetTime(base::TimeDelta current_time, base::TimeDelta max_time) {
  46   DCHECK(current_time <= max_time);
  47   DCHECK(current_time != kNoTimestamp());
  48
  49   UpdateReferencePoints(current_time);
  50   max_time_ = ClampToValidTimeRange(max_time);
  51   underflow_ = false;
  52 }
  53
  54 base::TimeDelta Clock::Elapsed() {
  55   if (duration_ == kNoTimestamp())
  56     return base::TimeDelta();
  57
  58   // The clock is not advancing, so return the last recorded time.
  59   if (!playing_ || underflow_)
  60     return media_time_;
  61
  62   base::TimeDelta elapsed = EstimatedElapsedTime();
  63   if (max_time_ != kNoTimestamp() && elapsed > max_time_) {
  64     UpdateReferencePoints(max_time_);
  65     underflow_ = true;
  66     elapsed = max_time_;
  67   }
  68
  69   return elapsed;
  70 }
  71
  72 void Clock::SetMaxTime(base::TimeDelta max_time) {
  73   DCHECK(max_time != kNoTimestamp());
  74
  75   UpdateReferencePoints();
  76   max_time_ = ClampToValidTimeRange(max_time);
  77
  78   underflow_ = media_time_ > max_time_;
  79   if (underflow_)
  80     media_time_ = max_time_;
  81 }
  82
  83 void Clock::SetDuration(base::TimeDelta duration) {
  84   DCHECK(duration > base::TimeDelta());
  85   duration_ = duration;
  86
  87   media_time_ = ClampToValidTimeRange(media_time_);
  88   if (max_time_ != kNoTimestamp())
  89     max_time_ = ClampToValidTimeRange(max_time_);
  90 }
  91
  92 base::TimeDelta Clock::ElapsedViaProvidedTime(
  93     const base::TimeTicks& time) const {
  94   // TODO(scherkus): floating point badness scaling time by playback rate.
  95   int64 now_us = (time - reference_).InMicroseconds();
  96   now_us = static_cast<int64>(now_us * playback_rate_);
  97   return media_time_ + base::TimeDelta::FromMicroseconds(now_us);
  98 }
  99
 100 base::TimeDelta Clock::ClampToValidTimeRange(base::TimeDelta time) const {
 101   if (duration_ == kNoTimestamp())
 102     return base::TimeDelta();
 103   return std::max(std::min(time, duration_), base::TimeDelta());
 104 }
 105
 106 void Clock::EndOfStream() {
 107   Pause();
 108   SetTime(Duration(), Duration());
 109 }
 110
 111 base::TimeDelta Clock::Duration() const {
 112   if (duration_ == kNoTimestamp())
 113     return base::TimeDelta();
 114   return duration_;
 115 }
 116
 117 void Clock::UpdateReferencePoints() {
 118   UpdateReferencePoints(Elapsed());
 119 }
 120
 121 void Clock::UpdateReferencePoints(base::TimeDelta current_time) {
 122   media_time_ = ClampToValidTimeRange(current_time);
 123   reference_ = clock_->NowTicks();
 124 }
 125
 126 base::TimeDelta Clock::EstimatedElapsedTime() {
 127   return ClampToValidTimeRange(ElapsedViaProvidedTime(clock_->NowTicks()));
 128 }
 129
 130 void Clock::Reset() {
 131   playing_ = false;
 132   playback_rate_ = 1.0f;
 133   max_time_ = kNoTimestamp();
 134   duration_ = kNoTimestamp();
 135   media_time_ = base::TimeDelta();
 136   reference_ = base::TimeTicks();
 137   underflow_ = false;
 138 }
 139
 140 }  // namespace media