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/*
* 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 <string>
#include <utility>
#include "absl/types/optional.h"
#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(absl::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(
absl::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(
absl::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,
absl::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