1 /* 2 * Copyright 2011 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 WEBRTC_BASE_BANDWIDTHSMOOTHER_H_ 12 #define WEBRTC_BASE_BANDWIDTHSMOOTHER_H_ 13 14 #include "webrtc/base/rollingaccumulator.h" 15 #include "webrtc/base/timeutils.h" 16 17 namespace rtc { 18 19 // The purpose of BandwidthSmoother is to smooth out bandwidth 20 // estimations so that 'trstate' messages can be triggered when we 21 // are "sure" there is sufficient bandwidth. To avoid frequent fluctuations, 22 // we take a slightly pessimistic view of our bandwidth. We only increase 23 // our estimation when we have sampled bandwidth measurements of values 24 // at least as large as the current estimation * percent_increase 25 // for at least time_between_increase time. If a sampled bandwidth 26 // is less than our current estimation we immediately decrease our estimation 27 // to that sampled value. 28 // We retain the initial bandwidth guess as our current bandwidth estimation 29 // until we have received (min_sample_count_percent * samples_count_to_average) 30 // number of samples. Min_sample_count_percent must be in range [0, 1]. 31 class BandwidthSmoother { 32 public: 33 BandwidthSmoother(int initial_bandwidth_guess, 34 uint32 time_between_increase, 35 double percent_increase, 36 size_t samples_count_to_average, 37 double min_sample_count_percent); 38 39 // Samples a new bandwidth measurement. 40 // bandwidth is expected to be non-negative. 41 // returns true if the bandwidth estimation changed 42 bool Sample(uint32 sample_time, int bandwidth); 43 44 int get_bandwidth_estimation() const { 45 return bandwidth_estimation_; 46 } 47 48 private: 49 uint32 time_between_increase_; 50 double percent_increase_; 51 uint32 time_at_last_change_; 52 int bandwidth_estimation_; 53 RollingAccumulator<int> accumulator_; 54 double min_sample_count_percent_; 55 }; 56 57 } // namespace rtc 58 59 #endif // WEBRTC_BASE_BANDWIDTHSMOOTHER_H_ 60
