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/*
* Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef RTC_BASE_NUMERICS_MOVING_MEDIAN_FILTER_H_
#define RTC_BASE_NUMERICS_MOVING_MEDIAN_FILTER_H_
#include <stddef.h>
#include <cstddef>
#include <list>
#include "rtc_base/checks.h"
#include "rtc_base/constructor_magic.h"
#include "rtc_base/numerics/percentile_filter.h"
namespace webrtc {
// Class to efficiently get moving median filter from a stream of samples.
template <typename T>
class MovingMedianFilter {
public:
// Construct filter. `window_size` is how many latest samples are stored and
// used to take median. `window_size` must be positive.
explicit MovingMedianFilter(size_t window_size);
// Insert a new sample.
void Insert(const T& value);
// Removes all samples;
void Reset();
// Get median over the latest window.
T GetFilteredValue() const;
// The number of samples that are currently stored.
size_t GetNumberOfSamplesStored() const;
private:
PercentileFilter<T> percentile_filter_;
std::list<T> samples_;
size_t samples_stored_;
const size_t window_size_;
RTC_DISALLOW_COPY_AND_ASSIGN(MovingMedianFilter);
};
template <typename T>
MovingMedianFilter<T>::MovingMedianFilter(size_t window_size)
: percentile_filter_(0.5f), samples_stored_(0), window_size_(window_size) {
RTC_CHECK_GT(window_size, 0);
}
template <typename T>
void MovingMedianFilter<T>::Insert(const T& value) {
percentile_filter_.Insert(value);
samples_.emplace_back(value);
++samples_stored_;
if (samples_stored_ > window_size_) {
percentile_filter_.Erase(samples_.front());
samples_.pop_front();
--samples_stored_;
}
}
template <typename T>
T MovingMedianFilter<T>::GetFilteredValue() const {
return percentile_filter_.GetPercentileValue();
}
template <typename T>
void MovingMedianFilter<T>::Reset() {
percentile_filter_.Reset();
samples_.clear();
samples_stored_ = 0;
}
template <typename T>
size_t MovingMedianFilter<T>::GetNumberOfSamplesStored() const {
return samples_stored_;
}
} // namespace webrtc
#endif // RTC_BASE_NUMERICS_MOVING_MEDIAN_FILTER_H_