webrtc/talk/base/bandwidthsmoother.cc

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/*
* 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