blob: 0f188e2ca146023a40db65e925064451ed447c9b [file] [log] [blame]
 // Copyright 2015 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #include "media/base/moving_average.h" #include namespace media { MovingAverage::MovingAverage(size_t depth) : depth_(depth), samples_(depth_) {} MovingAverage::~MovingAverage() = default; void MovingAverage::AddSample(base::TimeDelta sample) { // |samples_| is zero-initialized, so |oldest| is also zero before |count_| // exceeds |depth_|. base::TimeDelta& oldest = samples_[count_++ % depth_]; total_ += sample - oldest; oldest = sample; if (sample > max_) max_ = sample; } base::TimeDelta MovingAverage::Average() const { DCHECK_GT(count_, 0u); // TODO(dalecurtis): Consider limiting |depth| to powers of two so that we can // replace the integer divide with a bit shift operation. return total_ / std::min(static_cast(depth_), count_); } base::TimeDelta MovingAverage::Deviation() const { DCHECK_GT(count_, 0u); const base::TimeDelta average = Average(); const uint64_t size = std::min(static_cast(depth_), count_); // Perform the calculation in floating point since squaring the delta can // exceed the bounds of a uint64_t value given two int64_t inputs. double deviation_secs = 0; for (uint64_t i = 0; i < size; ++i) { const double x = (samples_[i] - average).InSecondsF(); deviation_secs += x * x; } deviation_secs /= size; return base::TimeDelta::FromSecondsD(std::sqrt(deviation_secs)); } void MovingAverage::Reset() { count_ = 0; total_ = base::TimeDelta(); max_ = kNoTimestamp; std::fill(samples_.begin(), samples_.end(), base::TimeDelta()); } } // namespace media