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 #include "webrtc/base/bandwidthsmoother.h" 12 13 #include <limits.h> 14 15 namespace rtc { 16 17 BandwidthSmoother::BandwidthSmoother(int initial_bandwidth_guess, 18 uint32 time_between_increase, 19 double percent_increase, 20 size_t samples_count_to_average, 21 double min_sample_count_percent) 22 : time_between_increase_(time_between_increase), 23 percent_increase_(rtc::_max(1.0, percent_increase)), 24 time_at_last_change_(0), 25 bandwidth_estimation_(initial_bandwidth_guess), 26 accumulator_(samples_count_to_average), 27 min_sample_count_percent_( 28 rtc::_min(1.0, 29 rtc::_max(0.0, min_sample_count_percent))) { 30 } 31 32 // Samples a new bandwidth measurement 33 // returns true if the bandwidth estimation changed 34 bool BandwidthSmoother::Sample(uint32 sample_time, int bandwidth) { 35 if (bandwidth < 0) { 36 return false; 37 } 38 39 accumulator_.AddSample(bandwidth); 40 41 if (accumulator_.count() < static_cast<size_t>( 42 accumulator_.max_count() * min_sample_count_percent_)) { 43 // We have not collected enough samples yet. 44 return false; 45 } 46 47 // Replace bandwidth with the mean of sampled bandwidths. 48 const int mean_bandwidth = static_cast<int>(accumulator_.ComputeMean()); 49 50 if (mean_bandwidth < bandwidth_estimation_) { 51 time_at_last_change_ = sample_time; 52 bandwidth_estimation_ = mean_bandwidth; 53 return true; 54 } 55 56 const int old_bandwidth_estimation = bandwidth_estimation_; 57 const double increase_threshold_d = percent_increase_ * bandwidth_estimation_; 58 if (increase_threshold_d > INT_MAX) { 59 // If bandwidth goes any higher we would overflow. 60 return false; 61 } 62 63 const int increase_threshold = static_cast<int>(increase_threshold_d); 64 if (mean_bandwidth < increase_threshold) { 65 time_at_last_change_ = sample_time; 66 // The value of bandwidth_estimation remains the same if we don't exceed 67 // percent_increase_ * bandwidth_estimation_ for at least 68 // time_between_increase_ time. 69 } else if (sample_time >= time_at_last_change_ + time_between_increase_) { 70 time_at_last_change_ = sample_time; 71 if (increase_threshold == 0) { 72 // Bandwidth_estimation_ must be zero. Assume a jump from zero to a 73 // positive bandwidth means we have regained connectivity. 74 bandwidth_estimation_ = mean_bandwidth; 75 } else { 76 bandwidth_estimation_ = increase_threshold; 77 } 78 } 79 // Else don't make a change. 80 81 return old_bandwidth_estimation != bandwidth_estimation_; 82 } 83 84 } // namespace rtc 85