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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 
Clock(base::TickClock * clock)15 Clock::Clock(base::TickClock* clock) : clock_(clock) {
16   DCHECK(clock_);
17   Reset();
18 }
19 
~Clock()20 Clock::~Clock() {}
21 
IsPlaying() const22 bool Clock::IsPlaying() const {
23   return playing_;
24 }
25 
Play()26 base::TimeDelta Clock::Play() {
27   DCHECK(!playing_);
28   UpdateReferencePoints();
29   playing_ = true;
30   return media_time_;
31 }
32 
Pause()33 base::TimeDelta Clock::Pause() {
34   DCHECK(playing_);
35   UpdateReferencePoints();
36   playing_ = false;
37   return media_time_;
38 }
39 
SetPlaybackRate(float playback_rate)40 void Clock::SetPlaybackRate(float playback_rate) {
41   UpdateReferencePoints();
42   playback_rate_ = playback_rate;
43 }
44 
SetTime(base::TimeDelta current_time,base::TimeDelta max_time)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 
Elapsed()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 
SetMaxTime(base::TimeDelta max_time)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 
SetDuration(base::TimeDelta duration)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 
ElapsedViaProvidedTime(const base::TimeTicks & time) const92 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 
ClampToValidTimeRange(base::TimeDelta time) const100 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 
EndOfStream()106 void Clock::EndOfStream() {
107   Pause();
108   SetTime(Duration(), Duration());
109 }
110 
Duration() const111 base::TimeDelta Clock::Duration() const {
112   if (duration_ == kNoTimestamp())
113     return base::TimeDelta();
114   return duration_;
115 }
116 
UpdateReferencePoints()117 void Clock::UpdateReferencePoints() {
118   UpdateReferencePoints(Elapsed());
119 }
120 
UpdateReferencePoints(base::TimeDelta current_time)121 void Clock::UpdateReferencePoints(base::TimeDelta current_time) {
122   media_time_ = ClampToValidTimeRange(current_time);
123   reference_ = clock_->NowTicks();
124 }
125 
EstimatedElapsedTime()126 base::TimeDelta Clock::EstimatedElapsedTime() {
127   return ClampToValidTimeRange(ElapsedViaProvidedTime(clock_->NowTicks()));
128 }
129 
Reset()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
141