src/media/base/time_delta_interpolator.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/time_delta_interpolator.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 TimeDeltaInterpolator::TimeDeltaInterpolator(base::TickClock* tick_clock)
  16     : tick_clock_(tick_clock),
  17       interpolating_(false),
  18       upper_bound_(kNoTimestamp()),
  19       playback_rate_(1.0f) {
  20   DCHECK(tick_clock_);
  21 }
  22
  23 TimeDeltaInterpolator::~TimeDeltaInterpolator() {
  24 }
  25
  26 base::TimeDelta TimeDeltaInterpolator::StartInterpolating() {
  27   DCHECK(!interpolating_);
  28   reference_ = tick_clock_->NowTicks();
  29   interpolating_ = true;
  30   return lower_bound_;
  31 }
  32
  33 base::TimeDelta TimeDeltaInterpolator::StopInterpolating() {
  34   DCHECK(interpolating_);
  35   lower_bound_ = GetInterpolatedTime();
  36   interpolating_ = false;
  37   return lower_bound_;
  38 }
  39
  40 void TimeDeltaInterpolator::SetPlaybackRate(float playback_rate) {
  41   lower_bound_ = GetInterpolatedTime();
  42   reference_ = tick_clock_->NowTicks();
  43   playback_rate_ = playback_rate;
  44 }
  45
  46 void TimeDeltaInterpolator::SetBounds(base::TimeDelta lower_bound,
  47                                       base::TimeDelta upper_bound) {
  48   DCHECK(lower_bound <= upper_bound);
  49   DCHECK(lower_bound != kNoTimestamp());
  50
  51   lower_bound_ = std::max(base::TimeDelta(), lower_bound);
  52   upper_bound_ = std::max(base::TimeDelta(), upper_bound);
  53   reference_ = tick_clock_->NowTicks();
  54 }
  55
  56 void TimeDeltaInterpolator::SetUpperBound(base::TimeDelta upper_bound) {
  57   DCHECK(upper_bound != kNoTimestamp());
  58
  59   lower_bound_ = GetInterpolatedTime();
  60   reference_ = tick_clock_->NowTicks();
  61   upper_bound_ = upper_bound;
  62 }
  63
  64 base::TimeDelta TimeDeltaInterpolator::GetInterpolatedTime() {
  65   if (!interpolating_)
  66     return lower_bound_;
  67
  68   int64 now_us = (tick_clock_->NowTicks() - reference_).InMicroseconds();
  69   now_us = static_cast<int64>(now_us * playback_rate_);
  70   base::TimeDelta interpolated_time =
  71       lower_bound_ + base::TimeDelta::FromMicroseconds(now_us);
  72
  73   if (upper_bound_ == kNoTimestamp())
  74     return interpolated_time;
  75
  76   return std::min(interpolated_time, upper_bound_);
  77 }
  78
  79 }  // namespace media