| /* |
| * 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 "webrtc/modules/congestion_controller/delay_based_bwe.h" |
| |
| #include <algorithm> |
| #include <cmath> |
| #include <string> |
| |
| #include "webrtc/base/checks.h" |
| #include "webrtc/base/constructormagic.h" |
| #include "webrtc/base/logging.h" |
| #include "webrtc/base/thread_annotations.h" |
| #include "webrtc/logging/rtc_event_log/rtc_event_log.h" |
| #include "webrtc/modules/congestion_controller/include/congestion_controller.h" |
| #include "webrtc/modules/pacing/paced_sender.h" |
| #include "webrtc/modules/remote_bitrate_estimator/include/remote_bitrate_estimator.h" |
| #include "webrtc/modules/remote_bitrate_estimator/test/bwe_test_logging.h" |
| #include "webrtc/system_wrappers/include/field_trial.h" |
| #include "webrtc/system_wrappers/include/metrics.h" |
| #include "webrtc/typedefs.h" |
| |
| namespace { |
| 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; |
| constexpr int kInitialRateWindowMs = 500; |
| constexpr int kRateWindowMs = 150; |
| |
| // 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; |
| |
| constexpr int kMaxConsecutiveFailedLookups = 5; |
| |
| const char kBweSparseUpdateExperiment[] = "WebRTC-BweSparseUpdateExperiment"; |
| |
| bool BweSparseUpdateExperimentIsEnabled() { |
| std::string experiment_string = |
| webrtc::field_trial::FindFullName(kBweSparseUpdateExperiment); |
| return experiment_string == "Enabled"; |
| } |
| |
| class PacketFeedbackComparator { |
| public: |
| inline bool operator()(const webrtc::PacketFeedback& lhs, |
| const webrtc::PacketFeedback& rhs) { |
| if (lhs.arrival_time_ms != rhs.arrival_time_ms) |
| return lhs.arrival_time_ms < rhs.arrival_time_ms; |
| if (lhs.send_time_ms != rhs.send_time_ms) |
| return lhs.send_time_ms < rhs.send_time_ms; |
| return lhs.sequence_number < rhs.sequence_number; |
| } |
| }; |
| |
| void SortPacketFeedbackVector(const std::vector<webrtc::PacketFeedback>& input, |
| std::vector<webrtc::PacketFeedback>* output) { |
| auto pred = [](const webrtc::PacketFeedback& packet_feedback) { |
| return packet_feedback.arrival_time_ms != |
| webrtc::PacketFeedback::kNotReceived; |
| }; |
| std::copy_if(input.begin(), input.end(), std::back_inserter(*output), pred); |
| std::sort(output->begin(), output->end(), PacketFeedbackComparator()); |
| } |
| } // namespace |
| |
| namespace webrtc { |
| |
| DelayBasedBwe::BitrateEstimator::BitrateEstimator() |
| : sum_(0), |
| current_win_ms_(0), |
| prev_time_ms_(-1), |
| bitrate_estimate_(-1.0f), |
| bitrate_estimate_var_(50.0f) {} |
| |
| void DelayBasedBwe::BitrateEstimator::Update(int64_t now_ms, int bytes) { |
| int rate_window_ms = kRateWindowMs; |
| // We use a larger window at the beginning to get a more stable sample that |
| // we can use to initialize the estimate. |
| if (bitrate_estimate_ < 0.f) |
| rate_window_ms = kInitialRateWindowMs; |
| float bitrate_sample = UpdateWindow(now_ms, bytes, rate_window_ms); |
| if (bitrate_sample < 0.0f) |
| return; |
| if (bitrate_estimate_ < 0.0f) { |
| // This is the very first sample we get. Use it to initialize the estimate. |
| bitrate_estimate_ = bitrate_sample; |
| return; |
| } |
| // Define the sample uncertainty as a function of how far away it is from the |
| // current estimate. |
| float sample_uncertainty = |
| 10.0f * std::abs(bitrate_estimate_ - bitrate_sample) / bitrate_estimate_; |
| float sample_var = sample_uncertainty * sample_uncertainty; |
| // Update a bayesian estimate of the rate, weighting it lower if the sample |
| // uncertainty is large. |
| // The bitrate estimate uncertainty is increased with each update to model |
| // that the bitrate changes over time. |
| float pred_bitrate_estimate_var = bitrate_estimate_var_ + 5.f; |
| bitrate_estimate_ = (sample_var * bitrate_estimate_ + |
| pred_bitrate_estimate_var * bitrate_sample) / |
| (sample_var + pred_bitrate_estimate_var); |
| bitrate_estimate_var_ = sample_var * pred_bitrate_estimate_var / |
| (sample_var + pred_bitrate_estimate_var); |
| } |
| |
| float DelayBasedBwe::BitrateEstimator::UpdateWindow(int64_t now_ms, |
| int bytes, |
| int rate_window_ms) { |
| // Reset if time moves backwards. |
| if (now_ms < prev_time_ms_) { |
| prev_time_ms_ = -1; |
| sum_ = 0; |
| current_win_ms_ = 0; |
| } |
| if (prev_time_ms_ >= 0) { |
| current_win_ms_ += now_ms - prev_time_ms_; |
| // Reset if nothing has been received for more than a full window. |
| if (now_ms - prev_time_ms_ > rate_window_ms) { |
| sum_ = 0; |
| current_win_ms_ %= rate_window_ms; |
| } |
| } |
| prev_time_ms_ = now_ms; |
| float bitrate_sample = -1.0f; |
| if (current_win_ms_ >= rate_window_ms) { |
| bitrate_sample = 8.0f * sum_ / static_cast<float>(rate_window_ms); |
| current_win_ms_ -= rate_window_ms; |
| sum_ = 0; |
| } |
| sum_ += bytes; |
| return bitrate_sample; |
| } |
| |
| rtc::Optional<uint32_t> DelayBasedBwe::BitrateEstimator::bitrate_bps() const { |
| if (bitrate_estimate_ < 0.f) |
| return rtc::Optional<uint32_t>(); |
| return rtc::Optional<uint32_t>(bitrate_estimate_ * 1000); |
| } |
| |
| DelayBasedBwe::DelayBasedBwe(RtcEventLog* event_log, const Clock* clock) |
| : event_log_(event_log), |
| clock_(clock), |
| inter_arrival_(), |
| trendline_estimator_(), |
| detector_(), |
| receiver_incoming_bitrate_(), |
| last_seen_packet_ms_(-1), |
| uma_recorded_(false), |
| probe_bitrate_estimator_(event_log), |
| trendline_window_size_(kDefaultTrendlineWindowSize), |
| trendline_smoothing_coeff_(kDefaultTrendlineSmoothingCoeff), |
| trendline_threshold_gain_(kDefaultTrendlineThresholdGain), |
| consecutive_delayed_feedbacks_(0), |
| last_logged_bitrate_(0), |
| last_logged_state_(BandwidthUsage::kBwNormal), |
| in_sparse_update_experiment_(BweSparseUpdateExperimentIsEnabled()) { |
| LOG(LS_INFO) << "Using Trendline filter for delay change estimation."; |
| network_thread_.DetachFromThread(); |
| } |
| |
| DelayBasedBwe::~DelayBasedBwe() {} |
| |
| DelayBasedBwe::Result DelayBasedBwe::IncomingPacketFeedbackVector( |
| const std::vector<PacketFeedback>& packet_feedback_vector) { |
| RTC_DCHECK(network_thread_.CalledOnValidThread()); |
| |
| std::vector<PacketFeedback> sorted_packet_feedback_vector; |
| SortPacketFeedbackVector(packet_feedback_vector, |
| &sorted_packet_feedback_vector); |
| // 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 (sorted_packet_feedback_vector.empty()) { |
| 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 overusing = false; |
| bool delayed_feedback = true; |
| for (const auto& packet_feedback : sorted_packet_feedback_vector) { |
| if (packet_feedback.send_time_ms < 0) |
| continue; |
| delayed_feedback = false; |
| IncomingPacketFeedback(packet_feedback); |
| if (!in_sparse_update_experiment_) |
| overusing |= (detector_.State() == BandwidthUsage::kBwOverusing); |
| } |
| if (in_sparse_update_experiment_) |
| overusing = (detector_.State() == BandwidthUsage::kBwOverusing); |
| if (delayed_feedback) { |
| ++consecutive_delayed_feedbacks_; |
| if (consecutive_delayed_feedbacks_ >= kMaxConsecutiveFailedLookups) { |
| consecutive_delayed_feedbacks_ = 0; |
| return OnLongFeedbackDelay( |
| sorted_packet_feedback_vector.back().arrival_time_ms); |
| } |
| } else { |
| consecutive_delayed_feedbacks_ = 0; |
| return MaybeUpdateEstimate(overusing); |
| } |
| return Result(); |
| } |
| |
| DelayBasedBwe::Result DelayBasedBwe::OnLongFeedbackDelay( |
| int64_t arrival_time_ms) { |
| // Estimate should always be valid since a start bitrate always is set in the |
| // Call constructor. An alternative would be to return an empty Result here, |
| // or to estimate the throughput based on the feedback we received. |
| RTC_DCHECK(rate_control_.ValidEstimate()); |
| rate_control_.SetEstimate(rate_control_.LatestEstimate() / 2, |
| arrival_time_ms); |
| Result result; |
| result.updated = true; |
| result.probe = false; |
| result.target_bitrate_bps = rate_control_.LatestEstimate(); |
| LOG(LS_WARNING) << "Long feedback delay detected, reducing BWE to " |
| << result.target_bitrate_bps; |
| return result; |
| } |
| |
| void DelayBasedBwe::IncomingPacketFeedback( |
| const PacketFeedback& packet_feedback) { |
| int64_t now_ms = clock_->TimeInMilliseconds(); |
| |
| receiver_incoming_bitrate_.Update(packet_feedback.arrival_time_ms, |
| packet_feedback.payload_size); |
| Result result; |
| // Reset if the stream has timed out. |
| if (last_seen_packet_ms_ == -1 || |
| now_ms - last_seen_packet_ms_ > kStreamTimeOutMs) { |
| inter_arrival_.reset( |
| new InterArrival((kTimestampGroupLengthMs << kInterArrivalShift) / 1000, |
| kTimestampToMs, true)); |
| trendline_estimator_.reset(new TrendlineEstimator( |
| trendline_window_size_, trendline_smoothing_coeff_, |
| trendline_threshold_gain_)); |
| } |
| last_seen_packet_ms_ = now_ms; |
| |
| 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, |
| now_ms, packet_feedback.payload_size, |
| &ts_delta, &t_delta, &size_delta)) { |
| double ts_delta_ms = (1000.0 * ts_delta) / (1 << kInterArrivalShift); |
| trendline_estimator_->Update(t_delta, ts_delta_ms, |
| packet_feedback.arrival_time_ms); |
| detector_.Detect(trendline_estimator_->trendline_slope(), ts_delta_ms, |
| trendline_estimator_->num_of_deltas(), |
| packet_feedback.arrival_time_ms); |
| } |
| if (packet_feedback.pacing_info.probe_cluster_id != |
| PacedPacketInfo::kNotAProbe) { |
| probe_bitrate_estimator_.HandleProbeAndEstimateBitrate(packet_feedback); |
| } |
| } |
| |
| DelayBasedBwe::Result DelayBasedBwe::MaybeUpdateEstimate(bool overusing) { |
| Result result; |
| int64_t now_ms = clock_->TimeInMilliseconds(); |
| |
| rtc::Optional<uint32_t> acked_bitrate_bps = |
| receiver_incoming_bitrate_.bitrate_bps(); |
| rtc::Optional<int> probe_bitrate_bps = |
| probe_bitrate_estimator_.FetchAndResetLastEstimatedBitrateBps(); |
| // Currently overusing the bandwidth. |
| if (overusing) { |
| if (acked_bitrate_bps && |
| rate_control_.TimeToReduceFurther(now_ms, *acked_bitrate_bps)) { |
| result.updated = UpdateEstimate(now_ms, acked_bitrate_bps, overusing, |
| &result.target_bitrate_bps); |
| } |
| } else { |
| if (probe_bitrate_bps) { |
| rate_control_.SetEstimate(*probe_bitrate_bps, now_ms); |
| result.probe = true; |
| } |
| result.updated = UpdateEstimate(now_ms, acked_bitrate_bps, overusing, |
| &result.target_bitrate_bps); |
| } |
| if (result.updated) { |
| BWE_TEST_LOGGING_PLOT(1, "target_bitrate_bps", now_ms, |
| result.target_bitrate_bps); |
| if (event_log_ && (result.target_bitrate_bps != last_logged_bitrate_ || |
| detector_.State() != last_logged_state_)) { |
| event_log_->LogDelayBasedBweUpdate(result.target_bitrate_bps, |
| detector_.State()); |
| last_logged_bitrate_ = result.target_bitrate_bps; |
| last_logged_state_ = detector_.State(); |
| } |
| } |
| return result; |
| } |
| |
| bool DelayBasedBwe::UpdateEstimate(int64_t now_ms, |
| rtc::Optional<uint32_t> acked_bitrate_bps, |
| bool overusing, |
| uint32_t* target_bitrate_bps) { |
| // TODO(terelius): RateControlInput::noise_var is deprecated and will be |
| // removed. In the meantime, we set it to zero. |
| const RateControlInput input( |
| overusing ? BandwidthUsage::kBwOverusing : detector_.State(), |
| acked_bitrate_bps, 0); |
| *target_bitrate_bps = rate_control_.Update(&input, now_ms); |
| return rate_control_.ValidEstimate(); |
| } |
| |
| void DelayBasedBwe::OnRttUpdate(int64_t avg_rtt_ms, int64_t max_rtt_ms) { |
| rate_control_.SetRtt(avg_rtt_ms); |
| } |
| |
| bool DelayBasedBwe::LatestEstimate(std::vector<uint32_t>* ssrcs, |
| uint32_t* bitrate_bps) 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_bps); |
| if (!rate_control_.ValidEstimate()) |
| return false; |
| |
| *ssrcs = {kFixedSsrc}; |
| *bitrate_bps = rate_control_.LatestEstimate(); |
| return true; |
| } |
| |
| void DelayBasedBwe::SetStartBitrate(int start_bitrate_bps) { |
| LOG(LS_WARNING) << "BWE Setting start bitrate to: " << start_bitrate_bps; |
| rate_control_.SetStartBitrate(start_bitrate_bps); |
| } |
| |
| void DelayBasedBwe::SetMinBitrate(int min_bitrate_bps) { |
| // 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_bps); |
| } |
| |
| int64_t DelayBasedBwe::GetExpectedBwePeriodMs() const { |
| return rate_control_.GetExpectedBandwidthPeriodMs(); |
| } |
| } // namespace webrtc |
