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Limit BWE drops from probes to 85% of the throughput estimate.

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Bug: webrtc:11498
Change-Id: Ia4bb1a3cbde951d7fce5f4408da481ee506f8d21
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/173180
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Commit-Queue: Björn Terelius <terelius@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31088}
This commit is contained in:
Bjorn Terelius 2020-04-16 14:13:12 +02:00 committed by Commit Bot
parent e886d2ebc3
commit efdff53176
3 changed files with 27 additions and 3 deletions
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27
modules/congestion_controller/goog_cc/goog_cc_network_control.cc
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@ -42,7 +42,13 @@ constexpr TimeDelta kLossUpdateInterval = TimeDelta::Millis(1000);
// the number of bytes that can be transmitted per interval.
// Increasing this factor will result in lower delays in cases of bitrate
// overshoots from the encoder.
const float kDefaultPaceMultiplier = 2.5f;
constexpr float kDefaultPaceMultiplier = 2.5f;
// If the probe result is far below the current throughput estimate
// it's unlikely that the probe is accurate, so we don't want to drop too far.
// However, if we actually are overusing, we want to drop to something slightly
// below the current throughput estimate to drain the network queues.
constexpr double kProbeDropThroughputFraction = 0.85;
int64_t GetBpsOrDefault(const absl::optional<DataRate>& rate,
int64_t fallback_bps) {
@ -75,6 +81,9 @@ GoogCcNetworkController::GoogCcNetworkController(NetworkControllerConfig config,
ignore_probes_lower_than_network_estimate_(IsNotDisabled(
key_value_config_,
"WebRTC-Bwe-IgnoreProbesLowerThanNetworkStateEstimate")),
limit_probes_lower_than_throughput_estimate_(
IsEnabled(key_value_config_,
"WebRTC-Bwe-LimitProbesLowerThanThroughputEstimate")),
rate_control_settings_(
RateControlSettings::ParseFromKeyValueConfig(key_value_config_)),
loss_based_stable_rate_(
@ -493,7 +502,7 @@ NetworkControlUpdate GoogCcNetworkController::OnTransportPacketsFeedback(
network_estimator_->OnTransportPacketsFeedback(report);
auto prev_estimate = estimate_;
estimate_ = network_estimator_->GetCurrentEstimate();
// TODO(srte): Make OnTransportPacketsFeedback signal wether the state
// TODO(srte): Make OnTransportPacketsFeedback signal whether the state
// changed to avoid the need for this check.
if (estimate_ && (!prev_estimate || estimate_->last_feed_time !=
prev_estimate->last_feed_time)) {
@ -508,6 +517,20 @@ NetworkControlUpdate GoogCcNetworkController::OnTransportPacketsFeedback(
*probe_bitrate < estimate_->link_capacity_lower) {
probe_bitrate.reset();
}
if (limit_probes_lower_than_throughput_estimate_ && probe_bitrate &&
acknowledged_bitrate) {
// Limit the backoff to something slightly below the acknowledged
// bitrate. ("Slightly below" because we want to drain the queues
// if we are actually overusing.)
// The acknowledged bitrate shouldn't normally be higher than the delay
// based estimate, but it could happen e.g. due to packet bursts or
// encoder overshoot. We use std::min to ensure that a probe result
// below the current BWE never causes an increase.
DataRate limit =
std::min(delay_based_bwe_->last_estimate(),
*acknowledged_bitrate * kProbeDropThroughputFraction);
probe_bitrate = std::max(*probe_bitrate, limit);
}
NetworkControlUpdate update;
bool recovered_from_overuse = false;

1
modules/congestion_controller/goog_cc/goog_cc_network_control.h
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@ -87,6 +87,7 @@ class GoogCcNetworkController : public NetworkControllerInterface {
FieldTrialFlag safe_reset_acknowledged_rate_;
const bool use_min_allocatable_as_lower_bound_;
const bool ignore_probes_lower_than_network_estimate_;
const bool limit_probes_lower_than_throughput_estimate_;
const RateControlSettings rate_control_settings_;
const bool loss_based_stable_rate_;

2
modules/congestion_controller/goog_cc/probe_bitrate_estimator.cc
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@ -179,7 +179,7 @@ absl::optional<DataRate> ProbeBitrateEstimator::HandleProbeAndEstimateBitrate(
std::make_unique<RtcEventProbeResultSuccess>(cluster_id, res.bps()));
}
estimated_data_rate_ = res;
return *estimated_data_rate_;
return estimated_data_rate_;
}
absl::optional<DataRate>