/* * libjingle * Copyright 2011, Google Inc. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * 1. Redistributions of source code must retain the above copyright notice, * this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * 3. The name of the author may not be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include "talk/base/bandwidthsmoother.h" #include <limits.h> namespace talk_base { BandwidthSmoother::BandwidthSmoother(int initial_bandwidth_guess, uint32 time_between_increase, double percent_increase, size_t samples_count_to_average, double min_sample_count_percent) : time_between_increase_(time_between_increase), percent_increase_(talk_base::_max(1.0, percent_increase)), time_at_last_change_(0), bandwidth_estimation_(initial_bandwidth_guess), accumulator_(samples_count_to_average), min_sample_count_percent_( talk_base::_min(1.0, talk_base::_max(0.0, min_sample_count_percent))) { } // Samples a new bandwidth measurement // returns true if the bandwidth estimation changed bool BandwidthSmoother::Sample(uint32 sample_time, int bandwidth) { if (bandwidth < 0) { return false; } accumulator_.AddSample(bandwidth); if (accumulator_.count() < static_cast<size_t>( accumulator_.max_count() * min_sample_count_percent_)) { // We have not collected enough samples yet. return false; } // Replace bandwidth with the mean of sampled bandwidths. const int mean_bandwidth = accumulator_.ComputeMean(); if (mean_bandwidth < bandwidth_estimation_) { time_at_last_change_ = sample_time; bandwidth_estimation_ = mean_bandwidth; return true; } const int old_bandwidth_estimation = bandwidth_estimation_; const double increase_threshold_d = percent_increase_ * bandwidth_estimation_; if (increase_threshold_d > INT_MAX) { // If bandwidth goes any higher we would overflow. return false; } const int increase_threshold = static_cast<int>(increase_threshold_d); if (mean_bandwidth < increase_threshold) { time_at_last_change_ = sample_time; // The value of bandwidth_estimation remains the same if we don't exceed // percent_increase_ * bandwidth_estimation_ for at least // time_between_increase_ time. } else if (sample_time >= time_at_last_change_ + time_between_increase_) { time_at_last_change_ = sample_time; if (increase_threshold == 0) { // Bandwidth_estimation_ must be zero. Assume a jump from zero to a // positive bandwidth means we have regained connectivity. bandwidth_estimation_ = mean_bandwidth; } else { bandwidth_estimation_ = increase_threshold; } } // Else don't make a change. return old_bandwidth_estimation != bandwidth_estimation_; } } // namespace talk_base