1cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)// Copyright 2014 The Chromium Authors. All rights reserved. 2cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)// Use of this source code is governed by a BSD-style license that can be 3cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)// found in the LICENSE file. 4cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) 5116680a4aac90f2aa7413d9095a592090648e557Ben Murdoch#include "media/cast/common/clock_drift_smoother.h" 6cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) 7cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)#include "base/logging.h" 8cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) 9cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)namespace media { 10cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)namespace cast { 11cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) 12cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)ClockDriftSmoother::ClockDriftSmoother(base::TimeDelta time_constant) 13cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) : time_constant_(time_constant), 14cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) estimate_us_(0.0) { 15cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) DCHECK(time_constant_ > base::TimeDelta()); 16cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)} 17cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) 18cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)ClockDriftSmoother::~ClockDriftSmoother() {} 19cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) 20cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)base::TimeDelta ClockDriftSmoother::Current() const { 21cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) DCHECK(!last_update_time_.is_null()); 22cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) return base::TimeDelta::FromMicroseconds( 23cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) static_cast<int64>(estimate_us_ + 0.5)); // Round to nearest microsecond. 24cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)} 25cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) 26cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)void ClockDriftSmoother::Reset(base::TimeTicks now, 27cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) base::TimeDelta measured_offset) { 28cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) DCHECK(!now.is_null()); 29cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) last_update_time_ = now; 30cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) estimate_us_ = measured_offset.InMicroseconds(); 31cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)} 32cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) 33cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)void ClockDriftSmoother::Update(base::TimeTicks now, 34cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) base::TimeDelta measured_offset) { 35cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) DCHECK(!now.is_null()); 36cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) if (last_update_time_.is_null()) { 37cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) Reset(now, measured_offset); 38cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) } else if (now < last_update_time_) { 39cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) // |now| is not monotonically non-decreasing. 40cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) NOTREACHED(); 41cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) } else { 42cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) const double elapsed_us = (now - last_update_time_).InMicroseconds(); 43cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) last_update_time_ = now; 44cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) const double weight = 45cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) elapsed_us / (elapsed_us + time_constant_.InMicroseconds()); 46cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) estimate_us_ = weight * measured_offset.InMicroseconds() + 47cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) (1.0 - weight) * estimate_us_; 48cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) } 49cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)} 50cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) 51cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)// static 52cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)base::TimeDelta ClockDriftSmoother::GetDefaultTimeConstant() { 53cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) static const int kDefaultTimeConstantInSeconds = 30; 54cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) return base::TimeDelta::FromSeconds(kDefaultTimeConstantInSeconds); 55cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)} 56cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles) 57cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)} // namespace cast 58cedac228d2dd51db4b79ea1e72c7f249408ee061Torne (Richard Coles)} // namespace media 59