| /* |
| * Copyright (c) 2012 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/send_side_bandwidth_estimation.h" |
| |
| #include <algorithm> |
| #include <cmath> |
| #include <cstdint> |
| #include <cstdio> |
| #include <limits> |
| #include <memory> |
| #include <optional> |
| #include <string> |
| #include <utility> |
| |
| #include "api/field_trials_view.h" |
| #include "api/rtc_event_log/rtc_event_log.h" |
| #include "api/transport/bandwidth_usage.h" |
| #include "api/transport/network_types.h" |
| #include "api/units/data_rate.h" |
| #include "api/units/time_delta.h" |
| #include "api/units/timestamp.h" |
| #include "logging/rtc_event_log/events/rtc_event_bwe_update_loss_based.h" |
| #include "modules/congestion_controller/goog_cc/loss_based_bwe_v2.h" |
| #include "modules/remote_bitrate_estimator/include/bwe_defines.h" |
| #include "rtc_base/checks.h" |
| #include "rtc_base/experiments/field_trial_parser.h" |
| #include "rtc_base/logging.h" |
| #include "system_wrappers/include/metrics.h" |
| |
| namespace webrtc { |
| namespace { |
| constexpr TimeDelta kBweIncreaseInterval = TimeDelta::Millis(1000); |
| constexpr TimeDelta kBweDecreaseInterval = TimeDelta::Millis(300); |
| constexpr TimeDelta kStartPhase = TimeDelta::Millis(2000); |
| constexpr TimeDelta kBweConverganceTime = TimeDelta::Millis(20000); |
| constexpr int kLimitNumPackets = 20; |
| constexpr DataRate kDefaultMaxBitrate = DataRate::BitsPerSec(1000000000); |
| constexpr TimeDelta kLowBitrateLogPeriod = TimeDelta::Millis(10000); |
| constexpr TimeDelta kRtcEventLogPeriod = TimeDelta::Millis(5000); |
| // Expecting that RTCP feedback is sent uniformly within [0.5, 1.5]s intervals. |
| constexpr TimeDelta kMaxRtcpFeedbackInterval = TimeDelta::Millis(5000); |
| |
| constexpr float kDefaultLowLossThreshold = 0.02f; |
| constexpr float kDefaultHighLossThreshold = 0.1f; |
| constexpr DataRate kDefaultBitrateThreshold = DataRate::Zero(); |
| |
| struct UmaRampUpMetric { |
| const char* metric_name; |
| int bitrate_kbps; |
| }; |
| |
| const UmaRampUpMetric kUmaRampupMetrics[] = { |
| {"WebRTC.BWE.RampUpTimeTo500kbpsInMs", 500}, |
| {"WebRTC.BWE.RampUpTimeTo1000kbpsInMs", 1000}, |
| {"WebRTC.BWE.RampUpTimeTo2000kbpsInMs", 2000}}; |
| const size_t kNumUmaRampupMetrics = |
| sizeof(kUmaRampupMetrics) / sizeof(kUmaRampupMetrics[0]); |
| |
| const char kBweLosExperiment[] = "WebRTC-BweLossExperiment"; |
| |
| bool BweLossExperimentIsEnabled(const FieldTrialsView& field_trials) { |
| return field_trials.IsEnabled(kBweLosExperiment); |
| } |
| |
| bool ReadBweLossExperimentParameters(const FieldTrialsView& field_trials, |
| float* low_loss_threshold, |
| float* high_loss_threshold, |
| uint32_t* bitrate_threshold_kbps) { |
| RTC_DCHECK(low_loss_threshold); |
| RTC_DCHECK(high_loss_threshold); |
| RTC_DCHECK(bitrate_threshold_kbps); |
| std::string experiment_string = field_trials.Lookup(kBweLosExperiment); |
| int parsed_values = |
| sscanf(experiment_string.c_str(), "Enabled-%f,%f,%u", low_loss_threshold, |
| high_loss_threshold, bitrate_threshold_kbps); |
| if (parsed_values == 3) { |
| RTC_CHECK_GT(*low_loss_threshold, 0.0f) |
| << "Loss threshold must be greater than 0."; |
| RTC_CHECK_LE(*low_loss_threshold, 1.0f) |
| << "Loss threshold must be less than or equal to 1."; |
| RTC_CHECK_GT(*high_loss_threshold, 0.0f) |
| << "Loss threshold must be greater than 0."; |
| RTC_CHECK_LE(*high_loss_threshold, 1.0f) |
| << "Loss threshold must be less than or equal to 1."; |
| RTC_CHECK_LE(*low_loss_threshold, *high_loss_threshold) |
| << "The low loss threshold must be less than or equal to the high loss " |
| "threshold."; |
| RTC_CHECK_GE(*bitrate_threshold_kbps, 0) |
| << "Bitrate threshold can't be negative."; |
| RTC_CHECK_LT(*bitrate_threshold_kbps, |
| std::numeric_limits<int>::max() / 1000) |
| << "Bitrate must be smaller enough to avoid overflows."; |
| return true; |
| } |
| RTC_LOG(LS_WARNING) << "Failed to parse parameters for BweLossExperiment " |
| "experiment from field trial string. Using default."; |
| *low_loss_threshold = kDefaultLowLossThreshold; |
| *high_loss_threshold = kDefaultHighLossThreshold; |
| *bitrate_threshold_kbps = kDefaultBitrateThreshold.kbps(); |
| return false; |
| } |
| } // namespace |
| |
| void LinkCapacityTracker::UpdateDelayBasedEstimate( |
| Timestamp at_time, |
| DataRate delay_based_bitrate) { |
| if (delay_based_bitrate < last_delay_based_estimate_) { |
| capacity_estimate_bps_ = |
| std::min(capacity_estimate_bps_, delay_based_bitrate.bps<double>()); |
| last_link_capacity_update_ = at_time; |
| } |
| last_delay_based_estimate_ = delay_based_bitrate; |
| } |
| |
| void LinkCapacityTracker::OnStartingRate(DataRate start_rate) { |
| if (last_link_capacity_update_.IsInfinite()) |
| capacity_estimate_bps_ = start_rate.bps<double>(); |
| } |
| |
| void LinkCapacityTracker::OnRateUpdate(std::optional<DataRate> acknowledged, |
| DataRate target, |
| Timestamp at_time) { |
| if (!acknowledged) |
| return; |
| DataRate acknowledged_target = std::min(*acknowledged, target); |
| if (acknowledged_target.bps() > capacity_estimate_bps_) { |
| TimeDelta delta = at_time - last_link_capacity_update_; |
| double alpha = |
| delta.IsFinite() ? exp(-(delta / TimeDelta::Seconds(10))) : 0; |
| capacity_estimate_bps_ = alpha * capacity_estimate_bps_ + |
| (1 - alpha) * acknowledged_target.bps<double>(); |
| } |
| last_link_capacity_update_ = at_time; |
| } |
| |
| void LinkCapacityTracker::OnRttBackoff(DataRate backoff_rate, |
| Timestamp at_time) { |
| capacity_estimate_bps_ = |
| std::min(capacity_estimate_bps_, backoff_rate.bps<double>()); |
| last_link_capacity_update_ = at_time; |
| } |
| |
| DataRate LinkCapacityTracker::estimate() const { |
| return DataRate::BitsPerSec(capacity_estimate_bps_); |
| } |
| |
| RttBasedBackoff::RttBasedBackoff(const FieldTrialsView* key_value_config) |
| : disabled_("Disabled"), |
| configured_limit_("limit", TimeDelta::Seconds(3)), |
| drop_fraction_("fraction", 0.8), |
| drop_interval_("interval", TimeDelta::Seconds(1)), |
| bandwidth_floor_("floor", DataRate::KilobitsPerSec(5)), |
| rtt_limit_(TimeDelta::PlusInfinity()), |
| // By initializing this to plus infinity, we make sure that we never |
| // trigger rtt backoff unless packet feedback is enabled. |
| last_propagation_rtt_update_(Timestamp::PlusInfinity()), |
| last_propagation_rtt_(TimeDelta::Zero()), |
| last_packet_sent_(Timestamp::MinusInfinity()) { |
| ParseFieldTrial({&disabled_, &configured_limit_, &drop_fraction_, |
| &drop_interval_, &bandwidth_floor_}, |
| key_value_config->Lookup("WebRTC-Bwe-MaxRttLimit")); |
| if (!disabled_) { |
| rtt_limit_ = configured_limit_.Get(); |
| } |
| } |
| |
| void RttBasedBackoff::UpdatePropagationRtt(Timestamp at_time, |
| TimeDelta propagation_rtt) { |
| last_propagation_rtt_update_ = at_time; |
| last_propagation_rtt_ = propagation_rtt; |
| } |
| |
| bool RttBasedBackoff::IsRttAboveLimit() const { |
| return CorrectedRtt() > rtt_limit_; |
| } |
| |
| TimeDelta RttBasedBackoff::CorrectedRtt() const { |
| // Avoid timeout when no packets are being sent. |
| TimeDelta timeout_correction = std::max( |
| last_packet_sent_ - last_propagation_rtt_update_, TimeDelta::Zero()); |
| return timeout_correction + last_propagation_rtt_; |
| } |
| |
| RttBasedBackoff::~RttBasedBackoff() = default; |
| |
| SendSideBandwidthEstimation::SendSideBandwidthEstimation( |
| const FieldTrialsView* key_value_config, RtcEventLog* event_log) |
| : key_value_config_(key_value_config), |
| rtt_backoff_(key_value_config), |
| lost_packets_since_last_loss_update_(0), |
| expected_packets_since_last_loss_update_(0), |
| current_target_(DataRate::Zero()), |
| last_logged_target_(DataRate::Zero()), |
| min_bitrate_configured_(kCongestionControllerMinBitrate), |
| max_bitrate_configured_(kDefaultMaxBitrate), |
| last_low_bitrate_log_(Timestamp::MinusInfinity()), |
| has_decreased_since_last_fraction_loss_(false), |
| last_loss_feedback_(Timestamp::MinusInfinity()), |
| last_loss_packet_report_(Timestamp::MinusInfinity()), |
| last_fraction_loss_(0), |
| last_logged_fraction_loss_(0), |
| last_round_trip_time_(TimeDelta::Zero()), |
| receiver_limit_(DataRate::PlusInfinity()), |
| delay_based_limit_(DataRate::PlusInfinity()), |
| time_last_decrease_(Timestamp::MinusInfinity()), |
| first_report_time_(Timestamp::MinusInfinity()), |
| initially_lost_packets_(0), |
| bitrate_at_2_seconds_(DataRate::Zero()), |
| uma_update_state_(kNoUpdate), |
| uma_rtt_state_(kNoUpdate), |
| rampup_uma_stats_updated_(kNumUmaRampupMetrics, false), |
| event_log_(event_log), |
| last_rtc_event_log_(Timestamp::MinusInfinity()), |
| low_loss_threshold_(kDefaultLowLossThreshold), |
| high_loss_threshold_(kDefaultHighLossThreshold), |
| bitrate_threshold_(kDefaultBitrateThreshold), |
| loss_based_bandwidth_estimator_v1_(key_value_config), |
| loss_based_bandwidth_estimator_v2_(new LossBasedBweV2(key_value_config)), |
| loss_based_state_(LossBasedState::kDelayBasedEstimate), |
| disable_receiver_limit_caps_only_("Disabled") { |
| RTC_DCHECK(event_log); |
| if (BweLossExperimentIsEnabled(*key_value_config_)) { |
| uint32_t bitrate_threshold_kbps; |
| if (ReadBweLossExperimentParameters( |
| *key_value_config_, &low_loss_threshold_, &high_loss_threshold_, |
| &bitrate_threshold_kbps)) { |
| RTC_LOG(LS_INFO) << "Enabled BweLossExperiment with parameters " |
| << low_loss_threshold_ << ", " << high_loss_threshold_ |
| << ", " << bitrate_threshold_kbps; |
| bitrate_threshold_ = DataRate::KilobitsPerSec(bitrate_threshold_kbps); |
| } |
| } |
| ParseFieldTrial({&disable_receiver_limit_caps_only_}, |
| key_value_config->Lookup("WebRTC-Bwe-ReceiverLimitCapsOnly")); |
| if (LossBasedBandwidthEstimatorV2Enabled()) { |
| loss_based_bandwidth_estimator_v2_->SetMinMaxBitrate( |
| min_bitrate_configured_, max_bitrate_configured_); |
| } |
| } |
| |
| SendSideBandwidthEstimation::~SendSideBandwidthEstimation() {} |
| |
| void SendSideBandwidthEstimation::OnRouteChange() { |
| lost_packets_since_last_loss_update_ = 0; |
| expected_packets_since_last_loss_update_ = 0; |
| current_target_ = DataRate::Zero(); |
| min_bitrate_configured_ = kCongestionControllerMinBitrate; |
| max_bitrate_configured_ = kDefaultMaxBitrate; |
| last_low_bitrate_log_ = Timestamp::MinusInfinity(); |
| has_decreased_since_last_fraction_loss_ = false; |
| last_loss_feedback_ = Timestamp::MinusInfinity(); |
| last_loss_packet_report_ = Timestamp::MinusInfinity(); |
| last_fraction_loss_ = 0; |
| last_logged_fraction_loss_ = 0; |
| last_round_trip_time_ = TimeDelta::Zero(); |
| receiver_limit_ = DataRate::PlusInfinity(); |
| delay_based_limit_ = DataRate::PlusInfinity(); |
| time_last_decrease_ = Timestamp::MinusInfinity(); |
| first_report_time_ = Timestamp::MinusInfinity(); |
| initially_lost_packets_ = 0; |
| bitrate_at_2_seconds_ = DataRate::Zero(); |
| uma_update_state_ = kNoUpdate; |
| uma_rtt_state_ = kNoUpdate; |
| last_rtc_event_log_ = Timestamp::MinusInfinity(); |
| if (LossBasedBandwidthEstimatorV2Enabled() && |
| loss_based_bandwidth_estimator_v2_->UseInStartPhase()) { |
| loss_based_bandwidth_estimator_v2_.reset( |
| new LossBasedBweV2(key_value_config_)); |
| } |
| } |
| |
| void SendSideBandwidthEstimation::SetBitrates( |
| std::optional<DataRate> send_bitrate, |
| DataRate min_bitrate, |
| DataRate max_bitrate, |
| Timestamp at_time) { |
| SetMinMaxBitrate(min_bitrate, max_bitrate); |
| if (send_bitrate) { |
| link_capacity_.OnStartingRate(*send_bitrate); |
| SetSendBitrate(*send_bitrate, at_time); |
| } |
| } |
| |
| void SendSideBandwidthEstimation::SetSendBitrate(DataRate bitrate, |
| Timestamp at_time) { |
| RTC_DCHECK_GT(bitrate, DataRate::Zero()); |
| // Reset to avoid being capped by the estimate. |
| delay_based_limit_ = DataRate::PlusInfinity(); |
| UpdateTargetBitrate(bitrate, at_time); |
| // Clear last sent bitrate history so the new value can be used directly |
| // and not capped. |
| min_bitrate_history_.clear(); |
| } |
| |
| void SendSideBandwidthEstimation::SetMinMaxBitrate(DataRate min_bitrate, |
| DataRate max_bitrate) { |
| min_bitrate_configured_ = |
| std::max(min_bitrate, kCongestionControllerMinBitrate); |
| if (max_bitrate > DataRate::Zero() && max_bitrate.IsFinite()) { |
| max_bitrate_configured_ = std::max(min_bitrate_configured_, max_bitrate); |
| } else { |
| max_bitrate_configured_ = kDefaultMaxBitrate; |
| } |
| loss_based_bandwidth_estimator_v2_->SetMinMaxBitrate(min_bitrate_configured_, |
| max_bitrate_configured_); |
| } |
| |
| int SendSideBandwidthEstimation::GetMinBitrate() const { |
| return min_bitrate_configured_.bps<int>(); |
| } |
| |
| DataRate SendSideBandwidthEstimation::target_rate() const { |
| DataRate target = current_target_; |
| if (!disable_receiver_limit_caps_only_) |
| target = std::min(target, receiver_limit_); |
| return std::max(min_bitrate_configured_, target); |
| } |
| |
| LossBasedState SendSideBandwidthEstimation::loss_based_state() const { |
| return loss_based_state_; |
| } |
| |
| bool SendSideBandwidthEstimation::IsRttAboveLimit() const { |
| return rtt_backoff_.IsRttAboveLimit(); |
| } |
| |
| DataRate SendSideBandwidthEstimation::GetEstimatedLinkCapacity() const { |
| return link_capacity_.estimate(); |
| } |
| |
| void SendSideBandwidthEstimation::UpdateReceiverEstimate(Timestamp at_time, |
| DataRate bandwidth) { |
| // TODO(srte): Ensure caller passes PlusInfinity, not zero, to represent no |
| // limitation. |
| receiver_limit_ = bandwidth.IsZero() ? DataRate::PlusInfinity() : bandwidth; |
| ApplyTargetLimits(at_time); |
| } |
| |
| void SendSideBandwidthEstimation::UpdateDelayBasedEstimate(Timestamp at_time, |
| DataRate bitrate) { |
| link_capacity_.UpdateDelayBasedEstimate(at_time, bitrate); |
| // TODO(srte): Ensure caller passes PlusInfinity, not zero, to represent no |
| // limitation. |
| delay_based_limit_ = bitrate.IsZero() ? DataRate::PlusInfinity() : bitrate; |
| ApplyTargetLimits(at_time); |
| } |
| |
| void SendSideBandwidthEstimation::SetAcknowledgedRate( |
| std::optional<DataRate> acknowledged_rate, |
| Timestamp at_time) { |
| acknowledged_rate_ = acknowledged_rate; |
| if (!acknowledged_rate.has_value()) { |
| return; |
| } |
| if (LossBasedBandwidthEstimatorV1Enabled()) { |
| loss_based_bandwidth_estimator_v1_.UpdateAcknowledgedBitrate( |
| *acknowledged_rate, at_time); |
| } |
| if (LossBasedBandwidthEstimatorV2Enabled()) { |
| loss_based_bandwidth_estimator_v2_->SetAcknowledgedBitrate( |
| *acknowledged_rate); |
| } |
| } |
| |
| void SendSideBandwidthEstimation::UpdateLossBasedEstimator( |
| const TransportPacketsFeedback& report, |
| BandwidthUsage /* delay_detector_state */, |
| std::optional<DataRate> /* probe_bitrate */, |
| bool in_alr) { |
| if (LossBasedBandwidthEstimatorV1Enabled()) { |
| loss_based_bandwidth_estimator_v1_.UpdateLossStatistics( |
| report.packet_feedbacks, report.feedback_time); |
| } |
| if (LossBasedBandwidthEstimatorV2Enabled()) { |
| loss_based_bandwidth_estimator_v2_->UpdateBandwidthEstimate( |
| report.packet_feedbacks, delay_based_limit_, in_alr); |
| UpdateEstimate(report.feedback_time); |
| } |
| } |
| |
| void SendSideBandwidthEstimation::UpdatePacketsLost(int64_t packets_lost, |
| int64_t number_of_packets, |
| Timestamp at_time) { |
| last_loss_feedback_ = at_time; |
| if (first_report_time_.IsInfinite()) |
| first_report_time_ = at_time; |
| |
| // Check sequence number diff and weight loss report |
| if (number_of_packets > 0) { |
| int64_t expected = |
| expected_packets_since_last_loss_update_ + number_of_packets; |
| |
| // Don't generate a loss rate until it can be based on enough packets. |
| if (expected < kLimitNumPackets) { |
| // Accumulate reports. |
| expected_packets_since_last_loss_update_ = expected; |
| lost_packets_since_last_loss_update_ += packets_lost; |
| return; |
| } |
| |
| has_decreased_since_last_fraction_loss_ = false; |
| int64_t lost_q8 = |
| std::max<int64_t>(lost_packets_since_last_loss_update_ + packets_lost, |
| 0) |
| << 8; |
| last_fraction_loss_ = std::min<int>(lost_q8 / expected, 255); |
| |
| // Reset accumulators. |
| lost_packets_since_last_loss_update_ = 0; |
| expected_packets_since_last_loss_update_ = 0; |
| last_loss_packet_report_ = at_time; |
| UpdateEstimate(at_time); |
| } |
| |
| UpdateUmaStatsPacketsLost(at_time, packets_lost); |
| } |
| |
| void SendSideBandwidthEstimation::UpdateUmaStatsPacketsLost(Timestamp at_time, |
| int packets_lost) { |
| DataRate bitrate_kbps = |
| DataRate::KilobitsPerSec((current_target_.bps() + 500) / 1000); |
| for (size_t i = 0; i < kNumUmaRampupMetrics; ++i) { |
| if (!rampup_uma_stats_updated_[i] && |
| bitrate_kbps.kbps() >= kUmaRampupMetrics[i].bitrate_kbps) { |
| RTC_HISTOGRAMS_COUNTS_100000(i, kUmaRampupMetrics[i].metric_name, |
| (at_time - first_report_time_).ms()); |
| rampup_uma_stats_updated_[i] = true; |
| } |
| } |
| if (IsInStartPhase(at_time)) { |
| initially_lost_packets_ += packets_lost; |
| } else if (uma_update_state_ == kNoUpdate) { |
| uma_update_state_ = kFirstDone; |
| bitrate_at_2_seconds_ = bitrate_kbps; |
| RTC_HISTOGRAM_COUNTS("WebRTC.BWE.InitiallyLostPackets", |
| initially_lost_packets_, 0, 100, 50); |
| RTC_HISTOGRAM_COUNTS("WebRTC.BWE.InitialBandwidthEstimate", |
| bitrate_at_2_seconds_.kbps(), 0, 2000, 50); |
| } else if (uma_update_state_ == kFirstDone && |
| at_time - first_report_time_ >= kBweConverganceTime) { |
| uma_update_state_ = kDone; |
| int bitrate_diff_kbps = std::max( |
| bitrate_at_2_seconds_.kbps<int>() - bitrate_kbps.kbps<int>(), 0); |
| RTC_HISTOGRAM_COUNTS("WebRTC.BWE.InitialVsConvergedDiff", bitrate_diff_kbps, |
| 0, 2000, 50); |
| } |
| } |
| |
| void SendSideBandwidthEstimation::UpdateRtt(TimeDelta rtt, Timestamp at_time) { |
| // Update RTT if we were able to compute an RTT based on this RTCP. |
| // FlexFEC doesn't send RTCP SR, which means we won't be able to compute RTT. |
| if (rtt > TimeDelta::Zero()) |
| last_round_trip_time_ = rtt; |
| |
| if (!IsInStartPhase(at_time) && uma_rtt_state_ == kNoUpdate) { |
| uma_rtt_state_ = kDone; |
| RTC_HISTOGRAM_COUNTS("WebRTC.BWE.InitialRtt", rtt.ms<int>(), 0, 2000, 50); |
| } |
| } |
| |
| void SendSideBandwidthEstimation::UpdateEstimate(Timestamp at_time) { |
| if (rtt_backoff_.IsRttAboveLimit()) { |
| if (at_time - time_last_decrease_ >= rtt_backoff_.drop_interval_ && |
| current_target_ > rtt_backoff_.bandwidth_floor_) { |
| time_last_decrease_ = at_time; |
| DataRate new_bitrate = |
| std::max(current_target_ * rtt_backoff_.drop_fraction_, |
| rtt_backoff_.bandwidth_floor_.Get()); |
| link_capacity_.OnRttBackoff(new_bitrate, at_time); |
| UpdateTargetBitrate(new_bitrate, at_time); |
| return; |
| } |
| // TODO(srte): This is likely redundant in most cases. |
| ApplyTargetLimits(at_time); |
| return; |
| } |
| |
| // We trust the REMB and/or delay-based estimate during the first 2 seconds if |
| // we haven't had any packet loss reported, to allow startup bitrate probing. |
| if (last_fraction_loss_ == 0 && IsInStartPhase(at_time) && |
| !loss_based_bandwidth_estimator_v2_->ReadyToUseInStartPhase()) { |
| DataRate new_bitrate = current_target_; |
| // TODO(srte): We should not allow the new_bitrate to be larger than the |
| // receiver limit here. |
| if (receiver_limit_.IsFinite()) |
| new_bitrate = std::max(receiver_limit_, new_bitrate); |
| if (delay_based_limit_.IsFinite()) |
| new_bitrate = std::max(delay_based_limit_, new_bitrate); |
| if (LossBasedBandwidthEstimatorV1Enabled()) { |
| loss_based_bandwidth_estimator_v1_.Initialize(new_bitrate); |
| } |
| |
| if (new_bitrate != current_target_) { |
| min_bitrate_history_.clear(); |
| if (LossBasedBandwidthEstimatorV1Enabled()) { |
| min_bitrate_history_.push_back(std::make_pair(at_time, new_bitrate)); |
| } else { |
| min_bitrate_history_.push_back( |
| std::make_pair(at_time, current_target_)); |
| } |
| UpdateTargetBitrate(new_bitrate, at_time); |
| return; |
| } |
| } |
| UpdateMinHistory(at_time); |
| if (last_loss_packet_report_.IsInfinite()) { |
| // No feedback received. |
| // TODO(srte): This is likely redundant in most cases. |
| ApplyTargetLimits(at_time); |
| return; |
| } |
| |
| if (LossBasedBandwidthEstimatorV1ReadyForUse()) { |
| DataRate new_bitrate = loss_based_bandwidth_estimator_v1_.Update( |
| at_time, min_bitrate_history_.front().second, delay_based_limit_, |
| last_round_trip_time_); |
| UpdateTargetBitrate(new_bitrate, at_time); |
| return; |
| } |
| |
| if (LossBasedBandwidthEstimatorV2ReadyForUse()) { |
| LossBasedBweV2::Result result = |
| loss_based_bandwidth_estimator_v2_->GetLossBasedResult(); |
| loss_based_state_ = result.state; |
| UpdateTargetBitrate(result.bandwidth_estimate, at_time); |
| return; |
| } |
| |
| TimeDelta time_since_loss_packet_report = at_time - last_loss_packet_report_; |
| if (time_since_loss_packet_report < 1.2 * kMaxRtcpFeedbackInterval) { |
| // We only care about loss above a given bitrate threshold. |
| float loss = last_fraction_loss_ / 256.0f; |
| // We only make decisions based on loss when the bitrate is above a |
| // threshold. This is a crude way of handling loss which is uncorrelated |
| // to congestion. |
| if (current_target_ < bitrate_threshold_ || loss <= low_loss_threshold_) { |
| // Loss < 2%: Increase rate by 8% of the min bitrate in the last |
| // kBweIncreaseInterval. |
| // Note that by remembering the bitrate over the last second one can |
| // rampup up one second faster than if only allowed to start ramping |
| // at 8% per second rate now. E.g.: |
| // If sending a constant 100kbps it can rampup immediately to 108kbps |
| // whenever a receiver report is received with lower packet loss. |
| // If instead one would do: current_bitrate_ *= 1.08^(delta time), |
| // it would take over one second since the lower packet loss to achieve |
| // 108kbps. |
| DataRate new_bitrate = DataRate::BitsPerSec( |
| min_bitrate_history_.front().second.bps() * 1.08 + 0.5); |
| |
| // Add 1 kbps extra, just to make sure that we do not get stuck |
| // (gives a little extra increase at low rates, negligible at higher |
| // rates). |
| new_bitrate += DataRate::BitsPerSec(1000); |
| UpdateTargetBitrate(new_bitrate, at_time); |
| return; |
| } else if (current_target_ > bitrate_threshold_) { |
| if (loss <= high_loss_threshold_) { |
| // Loss between 2% - 10%: Do nothing. |
| } else { |
| // Loss > 10%: Limit the rate decreases to once a kBweDecreaseInterval |
| // + rtt. |
| if (!has_decreased_since_last_fraction_loss_ && |
| (at_time - time_last_decrease_) >= |
| (kBweDecreaseInterval + last_round_trip_time_)) { |
| time_last_decrease_ = at_time; |
| |
| // Reduce rate: |
| // newRate = rate * (1 - 0.5*lossRate); |
| // where packetLoss = 256*lossRate; |
| DataRate new_bitrate = DataRate::BitsPerSec( |
| (current_target_.bps() * |
| static_cast<double>(512 - last_fraction_loss_)) / |
| 512.0); |
| has_decreased_since_last_fraction_loss_ = true; |
| UpdateTargetBitrate(new_bitrate, at_time); |
| return; |
| } |
| } |
| } |
| } |
| // TODO(srte): This is likely redundant in most cases. |
| ApplyTargetLimits(at_time); |
| } |
| |
| void SendSideBandwidthEstimation::UpdatePropagationRtt( |
| Timestamp at_time, |
| TimeDelta propagation_rtt) { |
| rtt_backoff_.UpdatePropagationRtt(at_time, propagation_rtt); |
| } |
| |
| void SendSideBandwidthEstimation::OnSentPacket(const SentPacket& sent_packet) { |
| // Only feedback-triggering packets will be reported here. |
| rtt_backoff_.last_packet_sent_ = sent_packet.send_time; |
| } |
| |
| bool SendSideBandwidthEstimation::IsInStartPhase(Timestamp at_time) const { |
| return first_report_time_.IsInfinite() || |
| at_time - first_report_time_ < kStartPhase; |
| } |
| |
| void SendSideBandwidthEstimation::UpdateMinHistory(Timestamp at_time) { |
| // Remove old data points from history. |
| // Since history precision is in ms, add one so it is able to increase |
| // bitrate if it is off by as little as 0.5ms. |
| while (!min_bitrate_history_.empty() && |
| at_time - min_bitrate_history_.front().first + TimeDelta::Millis(1) > |
| kBweIncreaseInterval) { |
| min_bitrate_history_.pop_front(); |
| } |
| |
| // Typical minimum sliding-window algorithm: Pop values higher than current |
| // bitrate before pushing it. |
| while (!min_bitrate_history_.empty() && |
| current_target_ <= min_bitrate_history_.back().second) { |
| min_bitrate_history_.pop_back(); |
| } |
| |
| min_bitrate_history_.push_back(std::make_pair(at_time, current_target_)); |
| } |
| |
| DataRate SendSideBandwidthEstimation::GetUpperLimit() const { |
| DataRate upper_limit = delay_based_limit_; |
| if (disable_receiver_limit_caps_only_) |
| upper_limit = std::min(upper_limit, receiver_limit_); |
| return std::min(upper_limit, max_bitrate_configured_); |
| } |
| |
| void SendSideBandwidthEstimation::MaybeLogLowBitrateWarning(DataRate bitrate, |
| Timestamp at_time) { |
| if (at_time - last_low_bitrate_log_ > kLowBitrateLogPeriod) { |
| RTC_LOG(LS_WARNING) << "Estimated available bandwidth " << ToString(bitrate) |
| << " is below configured min bitrate " |
| << ToString(min_bitrate_configured_) << "."; |
| last_low_bitrate_log_ = at_time; |
| } |
| } |
| |
| void SendSideBandwidthEstimation::MaybeLogLossBasedEvent(Timestamp at_time) { |
| if (current_target_ != last_logged_target_ || |
| last_fraction_loss_ != last_logged_fraction_loss_ || |
| at_time - last_rtc_event_log_ > kRtcEventLogPeriod) { |
| event_log_->Log(std::make_unique<RtcEventBweUpdateLossBased>( |
| current_target_.bps(), last_fraction_loss_, |
| expected_packets_since_last_loss_update_)); |
| last_logged_fraction_loss_ = last_fraction_loss_; |
| last_logged_target_ = current_target_; |
| last_rtc_event_log_ = at_time; |
| } |
| } |
| |
| void SendSideBandwidthEstimation::UpdateTargetBitrate(DataRate new_bitrate, |
| Timestamp at_time) { |
| new_bitrate = std::min(new_bitrate, GetUpperLimit()); |
| if (new_bitrate < min_bitrate_configured_) { |
| MaybeLogLowBitrateWarning(new_bitrate, at_time); |
| new_bitrate = min_bitrate_configured_; |
| } |
| current_target_ = new_bitrate; |
| MaybeLogLossBasedEvent(at_time); |
| link_capacity_.OnRateUpdate(acknowledged_rate_, current_target_, at_time); |
| } |
| |
| void SendSideBandwidthEstimation::ApplyTargetLimits(Timestamp at_time) { |
| UpdateTargetBitrate(current_target_, at_time); |
| } |
| |
| bool SendSideBandwidthEstimation::LossBasedBandwidthEstimatorV1Enabled() const { |
| return loss_based_bandwidth_estimator_v1_.Enabled() && |
| !LossBasedBandwidthEstimatorV2Enabled(); |
| } |
| |
| bool SendSideBandwidthEstimation::LossBasedBandwidthEstimatorV1ReadyForUse() |
| const { |
| return LossBasedBandwidthEstimatorV1Enabled() && |
| loss_based_bandwidth_estimator_v1_.InUse(); |
| } |
| |
| bool SendSideBandwidthEstimation::LossBasedBandwidthEstimatorV2Enabled() const { |
| return loss_based_bandwidth_estimator_v2_->IsEnabled(); |
| } |
| |
| bool SendSideBandwidthEstimation::LossBasedBandwidthEstimatorV2ReadyForUse() |
| const { |
| return loss_based_bandwidth_estimator_v2_->IsReady(); |
| } |
| |
| bool SendSideBandwidthEstimation::PaceAtLossBasedEstimate() const { |
| return LossBasedBandwidthEstimatorV2ReadyForUse() && |
| loss_based_bandwidth_estimator_v2_->PaceAtLossBasedEstimate(); |
| } |
| |
| } // namespace webrtc |
