| /* |
| * 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 "absl/strings/match.h" |
| #include "api/units/data_rate.h" |
| #include "api/units/time_delta.h" |
| |
| namespace webrtc { |
| namespace { |
| const char kBweLossBasedControl[] = "WebRTC-Bwe-LossBasedControl"; |
| |
| // Expecting RTCP feedback to be sent with roughly 1s intervals, a 5s gap |
| // indicates a channel outage. |
| constexpr TimeDelta kMaxRtcpFeedbackInterval = TimeDelta::Millis(5000); |
| |
| // 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_NOTREACHED(); // 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_NOTREACHED(); |
| 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_NOTREACHED(); |
| return 1.0f; |
| } |
| return 1.0f - exp(interval / window * -1.0); |
| } |
| |
| bool IsEnabled(const webrtc::FieldTrialsView& key_value_config, |
| absl::string_view name) { |
| return absl::StartsWith(key_value_config.Lookup(name), "Enabled"); |
| } |
| |
| } // namespace |
| |
| LossBasedControlConfig::LossBasedControlConfig( |
| const FieldTrialsView* key_value_config) |
| : enabled(IsEnabled(*key_value_config, 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_reset("balance_reset", |
| DataRate::KilobitsPerSec(0.1)), |
| 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)) { |
| 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_reset, &loss_bandwidth_balance_exponent, |
| &allow_resets, &decrease_interval, &loss_report_timeout}, |
| key_value_config->Lookup(kBweLossBasedControl)); |
| } |
| LossBasedControlConfig::LossBasedControlConfig(const LossBasedControlConfig&) = |
| default; |
| LossBasedControlConfig::~LossBasedControlConfig() = default; |
| |
| LossBasedBandwidthEstimation::LossBasedBandwidthEstimation( |
| const FieldTrialsView* key_value_config) |
| : config_(key_value_config), |
| 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_NOTREACHED(); |
| return; |
| } |
| int loss_count = 0; |
| for (const auto& pkt : packet_results) { |
| loss_count += !pkt.IsReceived() ? 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); |
| } |
| } |
| |
| DataRate LossBasedBandwidthEstimation::Update(Timestamp at_time, |
| DataRate min_bitrate, |
| DataRate wanted_bitrate, |
| TimeDelta last_round_trip_time) { |
| if (loss_based_bitrate_.IsZero()) { |
| loss_based_bitrate_ = wanted_bitrate; |
| } |
| |
| // 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 packet lost reports are too old, dont increase bitrate. |
| const bool loss_report_valid = |
| at_time - last_loss_packet_report_ < 1.2 * kMaxRtcpFeedbackInterval; |
| |
| if (loss_report_valid && config_.allow_resets && |
| loss_estimate_for_increase < loss_reset_threshold()) { |
| loss_based_bitrate_ = wanted_bitrate; |
| } else if (loss_report_valid && |
| 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; |
| } |
| } |
| return loss_based_bitrate_; |
| } |
| |
| void LossBasedBandwidthEstimation::Initialize(DataRate bitrate) { |
| loss_based_bitrate_ = bitrate; |
| average_loss_ = 0; |
| average_loss_max_ = 0; |
| } |
| |
| double LossBasedBandwidthEstimation::loss_reset_threshold() const { |
| return LossFromBitrate(loss_based_bitrate_, |
| config_.loss_bandwidth_balance_reset, |
| config_.loss_bandwidth_balance_exponent); |
| } |
| |
| 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_; |
| } |
| } // namespace webrtc |
