28e2075280
trunk/talk git-svn-id: http://webrtc.googlecode.com/svn/trunk@4318 4adac7df-926f-26a2-2b94-8c16560cd09d
102 lines
4.0 KiB
C++
102 lines
4.0 KiB
C++
/*
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* libjingle
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* Copyright 2011, Google Inc.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
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* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "talk/base/bandwidthsmoother.h"
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#include <limits.h>
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namespace talk_base {
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BandwidthSmoother::BandwidthSmoother(int initial_bandwidth_guess,
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uint32 time_between_increase,
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double percent_increase,
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size_t samples_count_to_average,
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double min_sample_count_percent)
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: time_between_increase_(time_between_increase),
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percent_increase_(talk_base::_max(1.0, percent_increase)),
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time_at_last_change_(0),
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bandwidth_estimation_(initial_bandwidth_guess),
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accumulator_(samples_count_to_average),
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min_sample_count_percent_(
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talk_base::_min(1.0,
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talk_base::_max(0.0, min_sample_count_percent))) {
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}
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// Samples a new bandwidth measurement
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// returns true if the bandwidth estimation changed
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bool BandwidthSmoother::Sample(uint32 sample_time, int bandwidth) {
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if (bandwidth < 0) {
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return false;
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}
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accumulator_.AddSample(bandwidth);
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if (accumulator_.count() < static_cast<size_t>(
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accumulator_.max_count() * min_sample_count_percent_)) {
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// We have not collected enough samples yet.
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return false;
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}
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// Replace bandwidth with the mean of sampled bandwidths.
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const int mean_bandwidth = accumulator_.ComputeMean();
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if (mean_bandwidth < bandwidth_estimation_) {
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time_at_last_change_ = sample_time;
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bandwidth_estimation_ = mean_bandwidth;
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return true;
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}
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const int old_bandwidth_estimation = bandwidth_estimation_;
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const double increase_threshold_d = percent_increase_ * bandwidth_estimation_;
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if (increase_threshold_d > INT_MAX) {
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// If bandwidth goes any higher we would overflow.
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return false;
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}
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const int increase_threshold = static_cast<int>(increase_threshold_d);
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if (mean_bandwidth < increase_threshold) {
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time_at_last_change_ = sample_time;
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// The value of bandwidth_estimation remains the same if we don't exceed
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// percent_increase_ * bandwidth_estimation_ for at least
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// time_between_increase_ time.
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} else if (sample_time >= time_at_last_change_ + time_between_increase_) {
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time_at_last_change_ = sample_time;
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if (increase_threshold == 0) {
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// Bandwidth_estimation_ must be zero. Assume a jump from zero to a
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// positive bandwidth means we have regained connectivity.
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bandwidth_estimation_ = mean_bandwidth;
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} else {
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bandwidth_estimation_ = increase_threshold;
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}
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}
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// Else don't make a change.
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return old_bandwidth_estimation != bandwidth_estimation_;
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}
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} // namespace talk_base
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