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/*
* Copyright 2011 The WebRTC Project Authors. All rights reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "webrtc/base/bandwidthsmoother.h"
#include <limits.h>
#include <algorithm>
namespace rtc {
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_(std::max(1.0, percent_increase)),
time_at_last_change_(0),
bandwidth_estimation_(initial_bandwidth_guess),
accumulator_(samples_count_to_average),
min_sample_count_percent_(
std::min(1.0, std::max(0.0, min_sample_count_percent))) {
}
BandwidthSmoother::~BandwidthSmoother() = default;
// 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 = static_cast<int>(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 rtc