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/*
* Copyright (c) 2019 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 COMMON_VIDEO_FRAME_RATE_ESTIMATOR_H_
#define COMMON_VIDEO_FRAME_RATE_ESTIMATOR_H_
#include <deque>
#include "absl/types/optional.h"
#include "api/units/time_delta.h"
#include "api/units/timestamp.h"
namespace webrtc {
// Class used to estimate a frame-rate using inter-frame intervals.
// Some notes on usage:
// This class is intended to accurately estimate the frame rate during a
// continuous stream. Unlike a traditional rate estimator that looks at number
// of data points within a time window, if the input stops this implementation
// will not smoothly fall down towards 0. This is done so that the estimated
// fps is not affected by edge conditions like if we sample just before or just
// after the next frame.
// To avoid problems if a stream is stopped and restarted (where estimated fps
// could look too low), users of this class should explicitly call Reset() on
// restart.
// Also note that this class is not thread safe, it's up to the user to guard
// against concurrent access.
class FrameRateEstimator {
public:
explicit FrameRateEstimator(TimeDelta averaging_window);
// Insert a frame, potentially culling old frames that falls outside the
// averaging window.
void OnFrame(Timestamp time);
// Get the current average FPS, based on the frames currently in the window.
absl::optional<double> GetAverageFps() const;
// Move the window so it ends at `now`, and return the new fps estimate.
absl::optional<double> GetAverageFps(Timestamp now);
// Completely clear the averaging window.
void Reset();
private:
void CullOld(Timestamp now);
const TimeDelta averaging_window_;
std::deque<Timestamp> frame_times_;
};
} // namespace webrtc
#endif // COMMON_VIDEO_FRAME_RATE_ESTIMATOR_H_
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