| /* |
| * Copyright (c) 2016 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/delay_based_bwe.h" |
| |
| #include <algorithm> |
| #include <cstdint> |
| #include <cstdio> |
| #include <string> |
| |
| #include "absl/memory/memory.h" |
| #include "api/transport/network_types.h" // For PacedPacketInfo |
| #include "logging/rtc_event_log/events/rtc_event.h" |
| #include "logging/rtc_event_log/events/rtc_event_bwe_update_delay_based.h" |
| #include "logging/rtc_event_log/rtc_event_log.h" |
| #include "modules/congestion_controller/goog_cc/trendline_estimator.h" |
| #include "modules/remote_bitrate_estimator/test/bwe_test_logging.h" |
| #include "rtc_base/checks.h" |
| #include "rtc_base/logging.h" |
| #include "system_wrappers/include/field_trial.h" |
| #include "system_wrappers/include/metrics.h" |
| |
| namespace webrtc { |
| namespace { |
| constexpr TimeDelta kStreamTimeOut = TimeDelta::Seconds<2>(); |
| constexpr int kTimestampGroupLengthMs = 5; |
| constexpr int kAbsSendTimeFraction = 18; |
| constexpr int kAbsSendTimeInterArrivalUpshift = 8; |
| constexpr int kInterArrivalShift = |
| kAbsSendTimeFraction + kAbsSendTimeInterArrivalUpshift; |
| constexpr double kTimestampToMs = |
| 1000.0 / static_cast<double>(1 << kInterArrivalShift); |
| // This ssrc is used to fulfill the current API but will be removed |
| // after the API has been changed. |
| constexpr uint32_t kFixedSsrc = 0; |
| |
| // Parameters for linear least squares fit of regression line to noisy data. |
| constexpr size_t kDefaultTrendlineWindowSize = 20; |
| constexpr double kDefaultTrendlineSmoothingCoeff = 0.9; |
| constexpr double kDefaultTrendlineThresholdGain = 4.0; |
| |
| const char kBweWindowSizeInPacketsExperiment[] = |
| "WebRTC-BweWindowSizeInPackets"; |
| |
| size_t ReadTrendlineFilterWindowSize() { |
| std::string experiment_string = |
| webrtc::field_trial::FindFullName(kBweWindowSizeInPacketsExperiment); |
| size_t window_size; |
| int parsed_values = |
| sscanf(experiment_string.c_str(), "Enabled-%zu", &window_size); |
| if (parsed_values == 1) { |
| if (window_size > 1) |
| return window_size; |
| RTC_LOG(WARNING) << "Window size must be greater than 1."; |
| } |
| RTC_LOG(LS_WARNING) << "Failed to parse parameters for BweWindowSizeInPackets" |
| " experiment from field trial string. Using default."; |
| return kDefaultTrendlineWindowSize; |
| } |
| } // namespace |
| |
| DelayBasedBwe::Result::Result() |
| : updated(false), |
| probe(false), |
| target_bitrate(DataRate::Zero()), |
| recovered_from_overuse(false), |
| backoff_in_alr(false) {} |
| |
| DelayBasedBwe::Result::Result(bool probe, DataRate target_bitrate) |
| : updated(true), |
| probe(probe), |
| target_bitrate(target_bitrate), |
| recovered_from_overuse(false), |
| backoff_in_alr(false) {} |
| |
| DelayBasedBwe::Result::~Result() {} |
| |
| DelayBasedBwe::DelayBasedBwe(RtcEventLog* event_log) |
| : event_log_(event_log), |
| inter_arrival_(), |
| delay_detector_(), |
| last_seen_packet_(Timestamp::MinusInfinity()), |
| uma_recorded_(false), |
| trendline_window_size_( |
| webrtc::field_trial::IsEnabled(kBweWindowSizeInPacketsExperiment) |
| ? ReadTrendlineFilterWindowSize() |
| : kDefaultTrendlineWindowSize), |
| trendline_smoothing_coeff_(kDefaultTrendlineSmoothingCoeff), |
| trendline_threshold_gain_(kDefaultTrendlineThresholdGain), |
| prev_bitrate_(DataRate::Zero()), |
| prev_state_(BandwidthUsage::kBwNormal), |
| alr_limited_backoff_enabled_( |
| field_trial::IsEnabled("WebRTC-Bwe-AlrLimitedBackoff")) { |
| RTC_LOG(LS_INFO) |
| << "Using Trendline filter for delay change estimation with window size " |
| << trendline_window_size_; |
| delay_detector_.reset(new TrendlineEstimator(trendline_window_size_, |
| trendline_smoothing_coeff_, |
| trendline_threshold_gain_)); |
| } |
| |
| DelayBasedBwe::~DelayBasedBwe() {} |
| |
| DelayBasedBwe::Result DelayBasedBwe::IncomingPacketFeedbackVector( |
| const std::vector<PacketFeedback>& packet_feedback_vector, |
| absl::optional<DataRate> acked_bitrate, |
| absl::optional<DataRate> probe_bitrate, |
| bool in_alr, |
| Timestamp at_time) { |
| RTC_DCHECK(std::is_sorted(packet_feedback_vector.begin(), |
| packet_feedback_vector.end(), |
| PacketFeedbackComparator())); |
| RTC_DCHECK_RUNS_SERIALIZED(&network_race_); |
| |
| // TOOD(holmer): An empty feedback vector here likely means that |
| // all acks were too late and that the send time history had |
| // timed out. We should reduce the rate when this occurs. |
| if (packet_feedback_vector.empty()) { |
| RTC_LOG(LS_WARNING) << "Very late feedback received."; |
| return DelayBasedBwe::Result(); |
| } |
| |
| if (!uma_recorded_) { |
| RTC_HISTOGRAM_ENUMERATION(kBweTypeHistogram, |
| BweNames::kSendSideTransportSeqNum, |
| BweNames::kBweNamesMax); |
| uma_recorded_ = true; |
| } |
| bool delayed_feedback = true; |
| bool recovered_from_overuse = false; |
| BandwidthUsage prev_detector_state = delay_detector_->State(); |
| for (const auto& packet_feedback : packet_feedback_vector) { |
| if (packet_feedback.send_time_ms < 0) |
| continue; |
| delayed_feedback = false; |
| IncomingPacketFeedback(packet_feedback, at_time); |
| if (prev_detector_state == BandwidthUsage::kBwUnderusing && |
| delay_detector_->State() == BandwidthUsage::kBwNormal) { |
| recovered_from_overuse = true; |
| } |
| prev_detector_state = delay_detector_->State(); |
| } |
| |
| if (delayed_feedback) { |
| // TODO(bugs.webrtc.org/10125): Design a better mechanism to safe-guard |
| // against building very large network queues. |
| return Result(); |
| } |
| return MaybeUpdateEstimate(acked_bitrate, probe_bitrate, |
| recovered_from_overuse, in_alr, at_time); |
| } |
| |
| void DelayBasedBwe::IncomingPacketFeedback( |
| const PacketFeedback& packet_feedback, |
| Timestamp at_time) { |
| // Reset if the stream has timed out. |
| if (last_seen_packet_.IsInfinite() || |
| at_time - last_seen_packet_ > kStreamTimeOut) { |
| inter_arrival_.reset( |
| new InterArrival((kTimestampGroupLengthMs << kInterArrivalShift) / 1000, |
| kTimestampToMs, true)); |
| delay_detector_.reset(new TrendlineEstimator(trendline_window_size_, |
| trendline_smoothing_coeff_, |
| trendline_threshold_gain_)); |
| } |
| last_seen_packet_ = at_time; |
| |
| uint32_t send_time_24bits = |
| static_cast<uint32_t>( |
| ((static_cast<uint64_t>(packet_feedback.send_time_ms) |
| << kAbsSendTimeFraction) + |
| 500) / |
| 1000) & |
| 0x00FFFFFF; |
| // Shift up send time to use the full 32 bits that inter_arrival works with, |
| // so wrapping works properly. |
| uint32_t timestamp = send_time_24bits << kAbsSendTimeInterArrivalUpshift; |
| |
| uint32_t ts_delta = 0; |
| int64_t t_delta = 0; |
| int size_delta = 0; |
| if (inter_arrival_->ComputeDeltas(timestamp, packet_feedback.arrival_time_ms, |
| at_time.ms(), packet_feedback.payload_size, |
| &ts_delta, &t_delta, &size_delta)) { |
| double ts_delta_ms = (1000.0 * ts_delta) / (1 << kInterArrivalShift); |
| delay_detector_->Update(t_delta, ts_delta_ms, |
| packet_feedback.arrival_time_ms); |
| } |
| } |
| |
| DelayBasedBwe::Result DelayBasedBwe::MaybeUpdateEstimate( |
| absl::optional<DataRate> acked_bitrate, |
| absl::optional<DataRate> probe_bitrate, |
| bool recovered_from_overuse, |
| bool in_alr, |
| Timestamp at_time) { |
| Result result; |
| |
| // Currently overusing the bandwidth. |
| if (delay_detector_->State() == BandwidthUsage::kBwOverusing) { |
| if (in_alr && alr_limited_backoff_enabled_ && |
| rate_control_.TimeToReduceFurther(at_time, prev_bitrate_)) { |
| result.updated = |
| UpdateEstimate(at_time, prev_bitrate_, &result.target_bitrate); |
| result.backoff_in_alr = true; |
| } else if (acked_bitrate && |
| rate_control_.TimeToReduceFurther(at_time, *acked_bitrate)) { |
| result.updated = |
| UpdateEstimate(at_time, acked_bitrate, &result.target_bitrate); |
| } else if (!acked_bitrate && rate_control_.ValidEstimate() && |
| rate_control_.InitialTimeToReduceFurther(at_time)) { |
| // Overusing before we have a measured acknowledged bitrate. Reduce send |
| // rate by 50% every 200 ms. |
| // TODO(tschumim): Improve this and/or the acknowledged bitrate estimator |
| // so that we (almost) always have a bitrate estimate. |
| rate_control_.SetEstimate(rate_control_.LatestEstimate() / 2, at_time); |
| result.updated = true; |
| result.probe = false; |
| result.target_bitrate = rate_control_.LatestEstimate(); |
| } |
| } else { |
| if (probe_bitrate) { |
| result.probe = true; |
| result.updated = true; |
| result.target_bitrate = *probe_bitrate; |
| rate_control_.SetEstimate(*probe_bitrate, at_time); |
| } else { |
| result.updated = |
| UpdateEstimate(at_time, acked_bitrate, &result.target_bitrate); |
| result.recovered_from_overuse = recovered_from_overuse; |
| } |
| } |
| BandwidthUsage detector_state = delay_detector_->State(); |
| if ((result.updated && prev_bitrate_ != result.target_bitrate) || |
| detector_state != prev_state_) { |
| DataRate bitrate = result.updated ? result.target_bitrate : prev_bitrate_; |
| |
| BWE_TEST_LOGGING_PLOT(1, "target_bitrate_bps", at_time.ms(), bitrate.bps()); |
| |
| if (event_log_) { |
| event_log_->Log(absl::make_unique<RtcEventBweUpdateDelayBased>( |
| bitrate.bps(), detector_state)); |
| } |
| |
| prev_bitrate_ = bitrate; |
| prev_state_ = detector_state; |
| } |
| return result; |
| } |
| |
| bool DelayBasedBwe::UpdateEstimate(Timestamp at_time, |
| absl::optional<DataRate> acked_bitrate, |
| DataRate* target_rate) { |
| const RateControlInput input(delay_detector_->State(), acked_bitrate); |
| *target_rate = rate_control_.Update(&input, at_time); |
| return rate_control_.ValidEstimate(); |
| } |
| |
| void DelayBasedBwe::OnRttUpdate(TimeDelta avg_rtt) { |
| rate_control_.SetRtt(avg_rtt); |
| } |
| |
| bool DelayBasedBwe::LatestEstimate(std::vector<uint32_t>* ssrcs, |
| DataRate* bitrate) const { |
| // Currently accessed from both the process thread (see |
| // ModuleRtpRtcpImpl::Process()) and the configuration thread (see |
| // Call::GetStats()). Should in the future only be accessed from a single |
| // thread. |
| RTC_DCHECK(ssrcs); |
| RTC_DCHECK(bitrate); |
| if (!rate_control_.ValidEstimate()) |
| return false; |
| |
| *ssrcs = {kFixedSsrc}; |
| *bitrate = rate_control_.LatestEstimate(); |
| return true; |
| } |
| |
| void DelayBasedBwe::SetStartBitrate(DataRate start_bitrate) { |
| RTC_LOG(LS_INFO) << "BWE Setting start bitrate to: " |
| << ToString(start_bitrate); |
| rate_control_.SetStartBitrate(start_bitrate); |
| } |
| |
| void DelayBasedBwe::SetMinBitrate(DataRate min_bitrate) { |
| // Called from both the configuration thread and the network thread. Shouldn't |
| // be called from the network thread in the future. |
| rate_control_.SetMinBitrate(min_bitrate); |
| } |
| |
| TimeDelta DelayBasedBwe::GetExpectedBwePeriod() const { |
| return rate_control_.GetExpectedBandwidthPeriod(); |
| } |
| |
| void DelayBasedBwe::SetAlrLimitedBackoffExperiment(bool enabled) { |
| alr_limited_backoff_enabled_ = enabled; |
| } |
| |
| } // namespace webrtc |
