87 lines
3.0 KiB
C++
87 lines
3.0 KiB
C++
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/*
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* Copyright 2011 The WebRTC Project Authors. All rights reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "webrtc/base/bandwidthsmoother.h"
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#include <limits.h>
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#include <algorithm>
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namespace rtc {
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BandwidthSmoother::BandwidthSmoother(int initial_bandwidth_guess,
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uint32_t 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_(std::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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std::min(1.0, std::max(0.0, min_sample_count_percent))) {
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}
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BandwidthSmoother::~BandwidthSmoother() = default;
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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_t 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 = static_cast<int>(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 rtc
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