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338 lines
12 KiB
C++
338 lines
12 KiB
C++
/*
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* Copyright (c) 2014 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/modules/remote_bitrate_estimator/aimd_rate_control.h"
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#include <algorithm>
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#include <cassert>
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#include <cmath>
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#include "webrtc/modules/remote_bitrate_estimator/test/bwe_test_logging.h"
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namespace webrtc {
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static const int64_t kDefaultRttMs = 200;
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static const int64_t kLogIntervalMs = 1000;
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static const double kWithinIncomingBitrateHysteresis = 1.05;
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AimdRateControl::AimdRateControl(uint32_t min_bitrate_bps)
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: min_configured_bitrate_bps_(min_bitrate_bps),
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max_configured_bitrate_bps_(30000000),
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current_bitrate_bps_(max_configured_bitrate_bps_),
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max_hold_rate_bps_(0),
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avg_max_bitrate_kbps_(-1.0f),
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var_max_bitrate_kbps_(0.4f),
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rate_control_state_(kRcHold),
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came_from_state_(kRcDecrease),
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rate_control_region_(kRcMaxUnknown),
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time_last_bitrate_change_(-1),
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current_input_(kBwNormal, 0, 1.0),
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updated_(false),
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time_first_incoming_estimate_(-1),
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bitrate_is_initialized_(false),
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beta_(0.9f),
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rtt_(kDefaultRttMs),
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time_of_last_log_(-1) {}
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RateControlType AimdRateControl::GetControlType() const {
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return kAimdControl;
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}
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uint32_t AimdRateControl::GetMinBitrate() const {
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return min_configured_bitrate_bps_;
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}
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bool AimdRateControl::ValidEstimate() const {
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return bitrate_is_initialized_;
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}
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int64_t AimdRateControl::GetFeedbackInterval() const {
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// Estimate how often we can send RTCP if we allocate up to 5% of bandwidth
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// to feedback.
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static const int kRtcpSize = 80;
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int64_t interval = static_cast<int64_t>(
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kRtcpSize * 8.0 * 1000.0 / (0.05 * current_bitrate_bps_) + 0.5);
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const int64_t kMinFeedbackIntervalMs = 200;
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return std::min(std::max(interval, kMinFeedbackIntervalMs),
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kMaxFeedbackIntervalMs);
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}
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bool AimdRateControl::TimeToReduceFurther(int64_t time_now,
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uint32_t incoming_bitrate_bps) const {
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const int64_t bitrate_reduction_interval =
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std::max<int64_t>(std::min<int64_t>(rtt_, 200), 10);
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if (time_now - time_last_bitrate_change_ >= bitrate_reduction_interval) {
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return true;
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}
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if (ValidEstimate()) {
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const int threshold = static_cast<int>(kWithinIncomingBitrateHysteresis *
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incoming_bitrate_bps);
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const int bitrate_difference = LatestEstimate() - incoming_bitrate_bps;
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return bitrate_difference > threshold;
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}
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return false;
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}
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uint32_t AimdRateControl::LatestEstimate() const {
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return current_bitrate_bps_;
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}
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uint32_t AimdRateControl::UpdateBandwidthEstimate(int64_t now_ms) {
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current_bitrate_bps_ = ChangeBitrate(current_bitrate_bps_,
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current_input_._incomingBitRate,
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now_ms);
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if (now_ms - time_of_last_log_ > kLogIntervalMs) {
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time_of_last_log_ = now_ms;
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}
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return current_bitrate_bps_;
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}
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void AimdRateControl::SetRtt(int64_t rtt) {
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rtt_ = rtt;
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}
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RateControlRegion AimdRateControl::Update(const RateControlInput* input,
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int64_t now_ms) {
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assert(input);
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// Set the initial bit rate value to what we're receiving the first half
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// second.
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if (!bitrate_is_initialized_) {
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if (time_first_incoming_estimate_ < 0) {
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if (input->_incomingBitRate > 0) {
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time_first_incoming_estimate_ = now_ms;
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}
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} else if (now_ms - time_first_incoming_estimate_ > 500 &&
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input->_incomingBitRate > 0) {
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current_bitrate_bps_ = input->_incomingBitRate;
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bitrate_is_initialized_ = true;
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}
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}
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if (updated_ && current_input_._bwState == kBwOverusing) {
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// Only update delay factor and incoming bit rate. We always want to react
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// on an over-use.
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current_input_._noiseVar = input->_noiseVar;
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current_input_._incomingBitRate = input->_incomingBitRate;
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} else {
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updated_ = true;
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current_input_ = *input;
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}
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return rate_control_region_;
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}
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void AimdRateControl::SetEstimate(int bitrate_bps, int64_t now_ms) {
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updated_ = true;
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bitrate_is_initialized_ = true;
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current_bitrate_bps_ = ChangeBitrate(bitrate_bps, bitrate_bps, now_ms);
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}
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uint32_t AimdRateControl::ChangeBitrate(uint32_t current_bitrate_bps,
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uint32_t incoming_bitrate_bps,
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int64_t now_ms) {
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BWE_TEST_LOGGING_PLOT("estimated_incoming#1", -1,
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incoming_bitrate_bps / 1000);
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if (!updated_) {
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return current_bitrate_bps_;
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}
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updated_ = false;
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ChangeState(current_input_, now_ms);
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// Calculated here because it's used in multiple places.
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const float incoming_bitrate_kbps = incoming_bitrate_bps / 1000.0f;
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// Calculate the max bit rate std dev given the normalized
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// variance and the current incoming bit rate.
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const float std_max_bit_rate = sqrt(var_max_bitrate_kbps_ *
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avg_max_bitrate_kbps_);
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bool fast_recovery_after_hold = false;
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switch (rate_control_state_) {
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case kRcHold: {
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max_hold_rate_bps_ = std::max(max_hold_rate_bps_, incoming_bitrate_bps);
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break;
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}
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case kRcIncrease: {
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if (avg_max_bitrate_kbps_ >= 0) {
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if (incoming_bitrate_kbps > avg_max_bitrate_kbps_ +
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3 * std_max_bit_rate) {
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ChangeRegion(kRcMaxUnknown);
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avg_max_bitrate_kbps_ = -1.0;
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} else if (incoming_bitrate_kbps > avg_max_bitrate_kbps_ +
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2.5 * std_max_bit_rate) {
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ChangeRegion(kRcAboveMax);
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}
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}
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if (rate_control_region_ == kRcNearMax) {
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// Approximate the over-use estimator delay to 100 ms.
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const int64_t response_time = rtt_ + 100;
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uint32_t additive_increase_bps = AdditiveRateIncrease(
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now_ms, time_last_bitrate_change_, response_time);
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BWE_TEST_LOGGING_PLOT("add_increase#1", -1,
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additive_increase_bps / 1000);
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current_bitrate_bps += additive_increase_bps;
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} else {
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uint32_t multiplicative_increase_bps = MultiplicativeRateIncrease(
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now_ms, time_last_bitrate_change_, current_bitrate_bps);
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BWE_TEST_LOGGING_PLOT("mult_increase#1", -1,
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multiplicative_increase_bps / 1000);
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current_bitrate_bps += multiplicative_increase_bps;
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}
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if (max_hold_rate_bps_ > 0 &&
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beta_ * max_hold_rate_bps_ > current_bitrate_bps) {
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current_bitrate_bps = static_cast<uint32_t>(beta_ * max_hold_rate_bps_);
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avg_max_bitrate_kbps_ = beta_ * max_hold_rate_bps_ / 1000.0f;
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ChangeRegion(kRcNearMax);
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fast_recovery_after_hold = true;
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}
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max_hold_rate_bps_ = 0;
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time_last_bitrate_change_ = now_ms;
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break;
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}
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case kRcDecrease: {
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if (incoming_bitrate_bps < min_configured_bitrate_bps_) {
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current_bitrate_bps = min_configured_bitrate_bps_;
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} else {
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// Set bit rate to something slightly lower than max
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// to get rid of any self-induced delay.
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current_bitrate_bps = static_cast<uint32_t>(beta_ *
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incoming_bitrate_bps + 0.5);
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if (current_bitrate_bps > current_bitrate_bps_) {
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// Avoid increasing the rate when over-using.
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if (rate_control_region_ != kRcMaxUnknown) {
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current_bitrate_bps = static_cast<uint32_t>(
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beta_ * avg_max_bitrate_kbps_ * 1000 + 0.5f);
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}
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current_bitrate_bps = std::min(current_bitrate_bps,
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current_bitrate_bps_);
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}
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ChangeRegion(kRcNearMax);
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if (incoming_bitrate_kbps < avg_max_bitrate_kbps_ -
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3 * std_max_bit_rate) {
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avg_max_bitrate_kbps_ = -1.0f;
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}
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UpdateMaxBitRateEstimate(incoming_bitrate_kbps);
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}
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// Stay on hold until the pipes are cleared.
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ChangeState(kRcHold);
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time_last_bitrate_change_ = now_ms;
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break;
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}
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default:
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assert(false);
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}
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if (!fast_recovery_after_hold && (incoming_bitrate_bps > 100000 ||
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current_bitrate_bps > 150000) &&
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current_bitrate_bps > 1.5 * incoming_bitrate_bps) {
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// Allow changing the bit rate if we are operating at very low rates
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// Don't change the bit rate if the send side is too far off
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current_bitrate_bps = current_bitrate_bps_;
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time_last_bitrate_change_ = now_ms;
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}
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return current_bitrate_bps;
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}
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uint32_t AimdRateControl::MultiplicativeRateIncrease(
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int64_t now_ms, int64_t last_ms, uint32_t current_bitrate_bps) const {
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double alpha = 1.08;
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if (last_ms > -1) {
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int time_since_last_update_ms = std::min(static_cast<int>(now_ms - last_ms),
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1000);
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alpha = pow(alpha, time_since_last_update_ms / 1000.0);
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}
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uint32_t multiplicative_increase_bps = std::max(
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current_bitrate_bps * (alpha - 1.0), 1000.0);
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return multiplicative_increase_bps;
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}
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uint32_t AimdRateControl::AdditiveRateIncrease(
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int64_t now_ms, int64_t last_ms, int64_t response_time_ms) const {
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assert(response_time_ms > 0);
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double beta = 0.0;
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if (last_ms > 0) {
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beta = std::min((now_ms - last_ms) /
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static_cast<double>(response_time_ms), 1.0);
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}
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double bits_per_frame = static_cast<double>(current_bitrate_bps_) / 30.0;
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double packets_per_frame = std::ceil(bits_per_frame / (8.0 * 1200.0));
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double avg_packet_size_bits = bits_per_frame / packets_per_frame;
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uint32_t additive_increase_bps = std::max(
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1000.0, beta * avg_packet_size_bits);
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return additive_increase_bps;
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}
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void AimdRateControl::UpdateMaxBitRateEstimate(float incoming_bitrate_kbps) {
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const float alpha = 0.05f;
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if (avg_max_bitrate_kbps_ == -1.0f) {
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avg_max_bitrate_kbps_ = incoming_bitrate_kbps;
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} else {
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avg_max_bitrate_kbps_ = (1 - alpha) * avg_max_bitrate_kbps_ +
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alpha * incoming_bitrate_kbps;
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}
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// Estimate the max bit rate variance and normalize the variance
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// with the average max bit rate.
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const float norm = std::max(avg_max_bitrate_kbps_, 1.0f);
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var_max_bitrate_kbps_ = (1 - alpha) * var_max_bitrate_kbps_ +
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alpha * (avg_max_bitrate_kbps_ - incoming_bitrate_kbps) *
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(avg_max_bitrate_kbps_ - incoming_bitrate_kbps) / norm;
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// 0.4 ~= 14 kbit/s at 500 kbit/s
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if (var_max_bitrate_kbps_ < 0.4f) {
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var_max_bitrate_kbps_ = 0.4f;
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}
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// 2.5f ~= 35 kbit/s at 500 kbit/s
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if (var_max_bitrate_kbps_ > 2.5f) {
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var_max_bitrate_kbps_ = 2.5f;
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}
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}
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void AimdRateControl::ChangeState(const RateControlInput& input,
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int64_t now_ms) {
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switch (current_input_._bwState) {
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case kBwNormal:
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if (rate_control_state_ == kRcHold) {
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time_last_bitrate_change_ = now_ms;
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ChangeState(kRcIncrease);
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}
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break;
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case kBwOverusing:
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if (rate_control_state_ != kRcDecrease) {
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ChangeState(kRcDecrease);
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}
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break;
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case kBwUnderusing:
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ChangeState(kRcHold);
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break;
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default:
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assert(false);
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}
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}
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void AimdRateControl::ChangeRegion(RateControlRegion region) {
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rate_control_region_ = region;
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switch (rate_control_region_) {
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case kRcAboveMax:
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case kRcMaxUnknown:
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beta_ = 0.9f;
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break;
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case kRcNearMax:
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beta_ = 0.95f;
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break;
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default:
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assert(false);
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}
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}
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void AimdRateControl::ChangeState(RateControlState new_state) {
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came_from_state_ = rate_control_state_;
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rate_control_state_ = new_state;
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}
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} // namespace webrtc
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