/* * 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. */ #ifndef TALK_BASE_BANDWIDTHSMOOTHER_H_ #define TALK_BASE_BANDWIDTHSMOOTHER_H_ #include "talk/base/rollingaccumulator.h" #include "talk/base/timeutils.h" namespace talk_base { // The purpose of BandwidthSmoother is to smooth out bandwidth // estimations so that 'trstate' messages can be triggered when we // are "sure" there is sufficient bandwidth. To avoid frequent fluctuations, // we take a slightly pessimistic view of our bandwidth. We only increase // our estimation when we have sampled bandwidth measurements of values // at least as large as the current estimation * percent_increase // for at least time_between_increase time. If a sampled bandwidth // is less than our current estimation we immediately decrease our estimation // to that sampled value. // We retain the initial bandwidth guess as our current bandwidth estimation // until we have received (min_sample_count_percent * samples_count_to_average) // number of samples. Min_sample_count_percent must be in range [0, 1]. class BandwidthSmoother { public: BandwidthSmoother(int initial_bandwidth_guess, uint32 time_between_increase, double percent_increase, size_t samples_count_to_average, double min_sample_count_percent); // Samples a new bandwidth measurement. // bandwidth is expected to be non-negative. // returns true if the bandwidth estimation changed bool Sample(uint32 sample_time, int bandwidth); int get_bandwidth_estimation() const { return bandwidth_estimation_; } private: uint32 time_between_increase_; double percent_increase_; uint32 time_at_last_change_; int bandwidth_estimation_; RollingAccumulator<int> accumulator_; double min_sample_count_percent_; }; } // namespace talk_base #endif // TALK_BASE_BANDWIDTHSMOOTHER_H_