modules/congestion_controller/goog_cc/loss_based_bandwidth_estimation.cc - src - Git at Google

 /*
  *  Copyright (c) 2018 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 "modules/congestion_controller/goog_cc/loss_based_bandwidth_estimation.h"

 #include <algorithm>
 #include <string>
 #include <vector>

 #include "api/units/data_rate.h"
 #include "api/units/time_delta.h"
 #include "system_wrappers/include/field_trial.h"

 namespace webrtc {
 namespace {
 const char kBweLossBasedControl[] = "WebRTC-Bwe-LossBasedControl";

 // Increase slower when RTT is high.
 double GetIncreaseFactor(const LossBasedControlConfig& config, TimeDelta rtt) {
   // Clamp the RTT
   if (rtt < config.increase_low_rtt) {
     rtt = config.increase_low_rtt;
   } else if (rtt > config.increase_high_rtt) {
     rtt = config.increase_high_rtt;
   }
   auto rtt_range = config.increase_high_rtt.Get() - config.increase_low_rtt;
   if (rtt_range <= TimeDelta::Zero()) {
     RTC_DCHECK(false);  // Only on misconfiguration.
     return config.min_increase_factor;
   }
   auto rtt_offset = rtt - config.increase_low_rtt;
   auto relative_offset = std::max(0.0, std::min(rtt_offset / rtt_range, 1.0));
   auto factor_range = config.max_increase_factor - config.min_increase_factor;
   return config.min_increase_factor + (1 - relative_offset) * factor_range;
 }

 double LossFromBitrate(DataRate bitrate,
                        DataRate loss_bandwidth_balance,
                        double exponent) {
   if (loss_bandwidth_balance >= bitrate)
     return 1.0;
   return pow(loss_bandwidth_balance / bitrate, exponent);
 }

 DataRate BitrateFromLoss(double loss,
                          DataRate loss_bandwidth_balance,
                          double exponent) {
   if (exponent <= 0) {
     RTC_DCHECK(false);
     return DataRate::Infinity();
   }
   if (loss < 1e-5)
     return DataRate::Infinity();
   return loss_bandwidth_balance * pow(loss, -1.0 / exponent);
 }

 double ExponentialUpdate(TimeDelta window, TimeDelta interval) {
   // Use the convention that exponential window length (which is really
   // infinite) is the time it takes to dampen to 1/e.
   if (window <= TimeDelta::Zero()) {
     RTC_DCHECK(false);
     return 1.0f;
   }
   return 1.0f - exp(interval / window * -1.0);
 }

 }  // namespace

 LossBasedControlConfig::LossBasedControlConfig()
     : enabled(field_trial::IsEnabled(kBweLossBasedControl)),
       min_increase_factor("min_incr", 1.02),
       max_increase_factor("max_incr", 1.08),
       increase_low_rtt("incr_low_rtt", TimeDelta::Millis(200)),
       increase_high_rtt("incr_high_rtt", TimeDelta::Millis(800)),
       decrease_factor("decr", 0.99),
       loss_window("loss_win", TimeDelta::Millis(800)),
       loss_max_window("loss_max_win", TimeDelta::Millis(800)),
       acknowledged_rate_max_window("ackrate_max_win", TimeDelta::Millis(800)),
       increase_offset("incr_offset", DataRate::BitsPerSec(1000)),
       loss_bandwidth_balance_increase("balance_incr",
                                       DataRate::KilobitsPerSec(0.5)),
       loss_bandwidth_balance_decrease("balance_decr",
                                       DataRate::KilobitsPerSec(4)),
       loss_bandwidth_balance_exponent("exponent", 0.5),
       allow_resets("resets", false),
       decrease_interval("decr_intvl", TimeDelta::Millis(300)),
       loss_report_timeout("timeout", TimeDelta::Millis(6000)) {
   std::string trial_string = field_trial::FindFullName(kBweLossBasedControl);
   ParseFieldTrial(
       {&min_increase_factor, &max_increase_factor, &increase_low_rtt,
        &increase_high_rtt, &decrease_factor, &loss_window, &loss_max_window,
        &acknowledged_rate_max_window, &increase_offset,
        &loss_bandwidth_balance_increase, &loss_bandwidth_balance_decrease,
        &loss_bandwidth_balance_exponent, &allow_resets, &decrease_interval,
        &loss_report_timeout},
       trial_string);
 }
 LossBasedControlConfig::LossBasedControlConfig(const LossBasedControlConfig&) =
     default;
 LossBasedControlConfig::~LossBasedControlConfig() = default;

 LossBasedBandwidthEstimation::LossBasedBandwidthEstimation()
     : config_(LossBasedControlConfig()),
       average_loss_(0),
       average_loss_max_(0),
       loss_based_bitrate_(DataRate::Zero()),
       acknowledged_bitrate_max_(DataRate::Zero()),
       acknowledged_bitrate_last_update_(Timestamp::MinusInfinity()),
       time_last_decrease_(Timestamp::MinusInfinity()),
       has_decreased_since_last_loss_report_(false),
       last_loss_packet_report_(Timestamp::MinusInfinity()),
       last_loss_ratio_(0) {}

 void LossBasedBandwidthEstimation::UpdateLossStatistics(
     const std::vector<PacketResult>& packet_results,
     Timestamp at_time) {
   if (packet_results.empty()) {
     RTC_DCHECK(false);
     return;
   }
   int loss_count = 0;
   for (const auto& pkt : packet_results) {
     loss_count += pkt.receive_time.IsInfinite() ? 1 : 0;
   }
   last_loss_ratio_ = static_cast<double>(loss_count) / packet_results.size();
   const TimeDelta time_passed = last_loss_packet_report_.IsFinite()
                                     ? at_time - last_loss_packet_report_
                                     : TimeDelta::Seconds(1);
   last_loss_packet_report_ = at_time;
   has_decreased_since_last_loss_report_ = false;

   average_loss_ += ExponentialUpdate(config_.loss_window, time_passed) *
                    (last_loss_ratio_ - average_loss_);
   if (average_loss_ > average_loss_max_) {
     average_loss_max_ = average_loss_;
   } else {
     average_loss_max_ +=
         ExponentialUpdate(config_.loss_max_window, time_passed) *
         (average_loss_ - average_loss_max_);
   }
 }

 void LossBasedBandwidthEstimation::UpdateAcknowledgedBitrate(
     DataRate acknowledged_bitrate,
     Timestamp at_time) {
   const TimeDelta time_passed =
       acknowledged_bitrate_last_update_.IsFinite()
           ? at_time - acknowledged_bitrate_last_update_
           : TimeDelta::Seconds(1);
   acknowledged_bitrate_last_update_ = at_time;
   if (acknowledged_bitrate > acknowledged_bitrate_max_) {
     acknowledged_bitrate_max_ = acknowledged_bitrate;
   } else {
     acknowledged_bitrate_max_ -=
         ExponentialUpdate(config_.acknowledged_rate_max_window, time_passed) *
         (acknowledged_bitrate_max_ - acknowledged_bitrate);
   }
 }

 void LossBasedBandwidthEstimation::Update(Timestamp at_time,
                                           DataRate min_bitrate,
                                           TimeDelta last_round_trip_time) {
   // Only increase if loss has been low for some time.
   const double loss_estimate_for_increase = average_loss_max_;
   // Avoid multiple decreases from averaging over one loss spike.
   const double loss_estimate_for_decrease =
       std::min(average_loss_, last_loss_ratio_);
   const bool allow_decrease =
       !has_decreased_since_last_loss_report_ &&
       (at_time - time_last_decrease_ >=
        last_round_trip_time + config_.decrease_interval);

   if (loss_estimate_for_increase < loss_increase_threshold()) {
     // Increase bitrate by RTT-adaptive ratio.
     DataRate new_increased_bitrate =
         min_bitrate * GetIncreaseFactor(config_, last_round_trip_time) +
         config_.increase_offset;
     // The bitrate that would make the loss "just high enough".
     const DataRate new_increased_bitrate_cap = BitrateFromLoss(
         loss_estimate_for_increase, config_.loss_bandwidth_balance_increase,
         config_.loss_bandwidth_balance_exponent);
     new_increased_bitrate =
         std::min(new_increased_bitrate, new_increased_bitrate_cap);
     loss_based_bitrate_ = std::max(new_increased_bitrate, loss_based_bitrate_);
   } else if (loss_estimate_for_decrease > loss_decrease_threshold() &&
              allow_decrease) {
     // The bitrate that would make the loss "just acceptable".
     const DataRate new_decreased_bitrate_floor = BitrateFromLoss(
         loss_estimate_for_decrease, config_.loss_bandwidth_balance_decrease,
         config_.loss_bandwidth_balance_exponent);
     DataRate new_decreased_bitrate =
         std::max(decreased_bitrate(), new_decreased_bitrate_floor);
     if (new_decreased_bitrate < loss_based_bitrate_) {
       time_last_decrease_ = at_time;
       has_decreased_since_last_loss_report_ = true;
       loss_based_bitrate_ = new_decreased_bitrate;
     }
   }
 }

 void LossBasedBandwidthEstimation::Reset(DataRate bitrate) {
   loss_based_bitrate_ = bitrate;
   average_loss_ = 0;
   average_loss_max_ = 0;
 }

 double LossBasedBandwidthEstimation::loss_increase_threshold() const {
   return LossFromBitrate(loss_based_bitrate_,
                          config_.loss_bandwidth_balance_increase,
                          config_.loss_bandwidth_balance_exponent);
 }

 double LossBasedBandwidthEstimation::loss_decrease_threshold() const {
   return LossFromBitrate(loss_based_bitrate_,
                          config_.loss_bandwidth_balance_decrease,
                          config_.loss_bandwidth_balance_exponent);
 }

 DataRate LossBasedBandwidthEstimation::decreased_bitrate() const {
   return config_.decrease_factor * acknowledged_bitrate_max_;
 }

 void LossBasedBandwidthEstimation::MaybeReset(DataRate bitrate) {
   if (config_.allow_resets)
     Reset(bitrate);
 }

 void LossBasedBandwidthEstimation::SetInitialBitrate(DataRate bitrate) {
   Reset(bitrate);
 }

 }  // namespace webrtc
	/*
	* Copyright (c) 2018 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 "modules/congestion_controller/goog_cc/loss_based_bandwidth_estimation.h"

	#include <algorithm>
	#include <string>
	#include <vector>

	#include "api/units/data_rate.h"
	#include "api/units/time_delta.h"
	#include "system_wrappers/include/field_trial.h"

	namespace webrtc {
	namespace {
	const char kBweLossBasedControl[] = "WebRTC-Bwe-LossBasedControl";

	// Increase slower when RTT is high.
	double GetIncreaseFactor(const LossBasedControlConfig& config, TimeDelta rtt) {
	// Clamp the RTT
	if (rtt < config.increase_low_rtt) {
	rtt = config.increase_low_rtt;
	} else if (rtt > config.increase_high_rtt) {
	rtt = config.increase_high_rtt;
	}
	auto rtt_range = config.increase_high_rtt.Get() - config.increase_low_rtt;
	if (rtt_range <= TimeDelta::Zero()) {
	RTC_DCHECK(false); // Only on misconfiguration.
	return config.min_increase_factor;
	}
	auto rtt_offset = rtt - config.increase_low_rtt;
	auto relative_offset = std::max(0.0, std::min(rtt_offset / rtt_range, 1.0));
	auto factor_range = config.max_increase_factor - config.min_increase_factor;
	return config.min_increase_factor + (1 - relative_offset) * factor_range;
	}

	double LossFromBitrate(DataRate bitrate,
	DataRate loss_bandwidth_balance,
	double exponent) {
	if (loss_bandwidth_balance >= bitrate)
	return 1.0;
	return pow(loss_bandwidth_balance / bitrate, exponent);
	}

	DataRate BitrateFromLoss(double loss,
	DataRate loss_bandwidth_balance,
	double exponent) {
	if (exponent <= 0) {
	RTC_DCHECK(false);
	return DataRate::Infinity();
	}
	if (loss < 1e-5)
	return DataRate::Infinity();
	return loss_bandwidth_balance * pow(loss, -1.0 / exponent);
	}

	double ExponentialUpdate(TimeDelta window, TimeDelta interval) {
	// Use the convention that exponential window length (which is really
	// infinite) is the time it takes to dampen to 1/e.
	if (window <= TimeDelta::Zero()) {
	RTC_DCHECK(false);
	return 1.0f;
	}
	return 1.0f - exp(interval / window * -1.0);
	}

	} // namespace

	LossBasedControlConfig::LossBasedControlConfig()
	: enabled(field_trial::IsEnabled(kBweLossBasedControl)),
	min_increase_factor("min_incr", 1.02),
	max_increase_factor("max_incr", 1.08),
	increase_low_rtt("incr_low_rtt", TimeDelta::Millis(200)),
	increase_high_rtt("incr_high_rtt", TimeDelta::Millis(800)),
	decrease_factor("decr", 0.99),
	loss_window("loss_win", TimeDelta::Millis(800)),
	loss_max_window("loss_max_win", TimeDelta::Millis(800)),
	acknowledged_rate_max_window("ackrate_max_win", TimeDelta::Millis(800)),
	increase_offset("incr_offset", DataRate::BitsPerSec(1000)),
	loss_bandwidth_balance_increase("balance_incr",
	DataRate::KilobitsPerSec(0.5)),
	loss_bandwidth_balance_decrease("balance_decr",
	DataRate::KilobitsPerSec(4)),
	loss_bandwidth_balance_exponent("exponent", 0.5),
	allow_resets("resets", false),
	decrease_interval("decr_intvl", TimeDelta::Millis(300)),
	loss_report_timeout("timeout", TimeDelta::Millis(6000)) {
	std::string trial_string = field_trial::FindFullName(kBweLossBasedControl);
	ParseFieldTrial(
	{&min_increase_factor, &max_increase_factor, &increase_low_rtt,
	&increase_high_rtt, &decrease_factor, &loss_window, &loss_max_window,
	&acknowledged_rate_max_window, &increase_offset,
	&loss_bandwidth_balance_increase, &loss_bandwidth_balance_decrease,
	&loss_bandwidth_balance_exponent, &allow_resets, &decrease_interval,
	&loss_report_timeout},
	trial_string);
	}
	LossBasedControlConfig::LossBasedControlConfig(const LossBasedControlConfig&) =
	default;
	LossBasedControlConfig::~LossBasedControlConfig() = default;

	LossBasedBandwidthEstimation::LossBasedBandwidthEstimation()
	: config_(LossBasedControlConfig()),
	average_loss_(0),
	average_loss_max_(0),
	loss_based_bitrate_(DataRate::Zero()),
	acknowledged_bitrate_max_(DataRate::Zero()),
	acknowledged_bitrate_last_update_(Timestamp::MinusInfinity()),
	time_last_decrease_(Timestamp::MinusInfinity()),
	has_decreased_since_last_loss_report_(false),
	last_loss_packet_report_(Timestamp::MinusInfinity()),
	last_loss_ratio_(0) {}

	void LossBasedBandwidthEstimation::UpdateLossStatistics(
	const std::vector<PacketResult>& packet_results,
	Timestamp at_time) {
	if (packet_results.empty()) {
	RTC_DCHECK(false);
	return;
	}
	int loss_count = 0;
	for (const auto& pkt : packet_results) {
	loss_count += pkt.receive_time.IsInfinite() ? 1 : 0;
	}
	last_loss_ratio_ = static_cast<double>(loss_count) / packet_results.size();
	const TimeDelta time_passed = last_loss_packet_report_.IsFinite()
	? at_time - last_loss_packet_report_
	: TimeDelta::Seconds(1);
	last_loss_packet_report_ = at_time;
	has_decreased_since_last_loss_report_ = false;

	average_loss_ += ExponentialUpdate(config_.loss_window, time_passed) *
	(last_loss_ratio_ - average_loss_);
	if (average_loss_ > average_loss_max_) {
	average_loss_max_ = average_loss_;
	} else {
	average_loss_max_ +=
	ExponentialUpdate(config_.loss_max_window, time_passed) *
	(average_loss_ - average_loss_max_);
	}
	}

	void LossBasedBandwidthEstimation::UpdateAcknowledgedBitrate(
	DataRate acknowledged_bitrate,
	Timestamp at_time) {
	const TimeDelta time_passed =
	acknowledged_bitrate_last_update_.IsFinite()
	? at_time - acknowledged_bitrate_last_update_
	: TimeDelta::Seconds(1);
	acknowledged_bitrate_last_update_ = at_time;
	if (acknowledged_bitrate > acknowledged_bitrate_max_) {
	acknowledged_bitrate_max_ = acknowledged_bitrate;
	} else {
	acknowledged_bitrate_max_ -=
	ExponentialUpdate(config_.acknowledged_rate_max_window, time_passed) *
	(acknowledged_bitrate_max_ - acknowledged_bitrate);
	}
	}

	void LossBasedBandwidthEstimation::Update(Timestamp at_time,
	DataRate min_bitrate,
	TimeDelta last_round_trip_time) {
	// Only increase if loss has been low for some time.
	const double loss_estimate_for_increase = average_loss_max_;
	// Avoid multiple decreases from averaging over one loss spike.
	const double loss_estimate_for_decrease =
	std::min(average_loss_, last_loss_ratio_);
	const bool allow_decrease =
	!has_decreased_since_last_loss_report_ &&
	(at_time - time_last_decrease_ >=
	last_round_trip_time + config_.decrease_interval);

	if (loss_estimate_for_increase < loss_increase_threshold()) {
	// Increase bitrate by RTT-adaptive ratio.
	DataRate new_increased_bitrate =
	min_bitrate * GetIncreaseFactor(config_, last_round_trip_time) +
	config_.increase_offset;
	// The bitrate that would make the loss "just high enough".
	const DataRate new_increased_bitrate_cap = BitrateFromLoss(
	loss_estimate_for_increase, config_.loss_bandwidth_balance_increase,
	config_.loss_bandwidth_balance_exponent);
	new_increased_bitrate =
	std::min(new_increased_bitrate, new_increased_bitrate_cap);
	loss_based_bitrate_ = std::max(new_increased_bitrate, loss_based_bitrate_);
	} else if (loss_estimate_for_decrease > loss_decrease_threshold() &&
	allow_decrease) {
	// The bitrate that would make the loss "just acceptable".
	const DataRate new_decreased_bitrate_floor = BitrateFromLoss(
	loss_estimate_for_decrease, config_.loss_bandwidth_balance_decrease,
	config_.loss_bandwidth_balance_exponent);
	DataRate new_decreased_bitrate =
	std::max(decreased_bitrate(), new_decreased_bitrate_floor);
	if (new_decreased_bitrate < loss_based_bitrate_) {
	time_last_decrease_ = at_time;
	has_decreased_since_last_loss_report_ = true;
	loss_based_bitrate_ = new_decreased_bitrate;
	}
	}
	}

	void LossBasedBandwidthEstimation::Reset(DataRate bitrate) {
	loss_based_bitrate_ = bitrate;
	average_loss_ = 0;
	average_loss_max_ = 0;
	}

	double LossBasedBandwidthEstimation::loss_increase_threshold() const {
	return LossFromBitrate(loss_based_bitrate_,
	config_.loss_bandwidth_balance_increase,
	config_.loss_bandwidth_balance_exponent);
	}

	double LossBasedBandwidthEstimation::loss_decrease_threshold() const {
	return LossFromBitrate(loss_based_bitrate_,
	config_.loss_bandwidth_balance_decrease,
	config_.loss_bandwidth_balance_exponent);
	}

	DataRate LossBasedBandwidthEstimation::decreased_bitrate() const {
	return config_.decrease_factor * acknowledged_bitrate_max_;
	}

	void LossBasedBandwidthEstimation::MaybeReset(DataRate bitrate) {
	if (config_.allow_resets)
	Reset(bitrate);
	}

	void LossBasedBandwidthEstimation::SetInitialBitrate(DataRate bitrate) {
	Reset(bitrate);
	}

	} // namespace webrtc