frame_rate_estimator.h (2150B)
1 /* 2 * Copyright (c) 2019 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #ifndef COMMON_VIDEO_FRAME_RATE_ESTIMATOR_H_ 12 #define COMMON_VIDEO_FRAME_RATE_ESTIMATOR_H_ 13 14 #include <deque> 15 #include <optional> 16 17 #include "api/units/time_delta.h" 18 #include "api/units/timestamp.h" 19 20 namespace webrtc { 21 22 // Class used to estimate a frame-rate using inter-frame intervals. 23 // Some notes on usage: 24 // This class is intended to accurately estimate the frame rate during a 25 // continuous stream. Unlike a traditional rate estimator that looks at number 26 // of data points within a time window, if the input stops this implementation 27 // will not smoothly fall down towards 0. This is done so that the estimated 28 // fps is not affected by edge conditions like if we sample just before or just 29 // after the next frame. 30 // To avoid problems if a stream is stopped and restarted (where estimated fps 31 // could look too low), users of this class should explicitly call Reset() on 32 // restart. 33 // Also note that this class is not thread safe, it's up to the user to guard 34 // against concurrent access. 35 class FrameRateEstimator { 36 public: 37 explicit FrameRateEstimator(TimeDelta averaging_window); 38 39 // Insert a frame, potentially culling old frames that falls outside the 40 // averaging window. 41 void OnFrame(Timestamp time); 42 43 // Get the current average FPS, based on the frames currently in the window. 44 std::optional<double> GetAverageFps() const; 45 46 // Move the window so it ends at `now`, and return the new fps estimate. 47 std::optional<double> GetAverageFps(Timestamp now); 48 49 // Completely clear the averaging window. 50 void Reset(); 51 52 private: 53 void CullOld(Timestamp now); 54 const TimeDelta averaging_window_; 55 std::deque<Timestamp> frame_times_; 56 }; 57 58 } // namespace webrtc 59 60 #endif // COMMON_VIDEO_FRAME_RATE_ESTIMATOR_H_