snapshot of https://github.com/livekit/livekit.git @ 08c5433449c106943231037d0b892895f6e92d3b (2026-09-15)

pkg/sfu/bwe/sendsidebwe/send_side_bwe.go

@@ -0,0 +1,151 @@
+// Copyright 2023 LiveKit, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package sendsidebwe
+
+import (
+	"time"
+
+	"github.com/livekit/livekit-server/pkg/sfu/bwe"
+	"github.com/livekit/livekit-server/pkg/sfu/ccutils"
+	"github.com/livekit/protocol/logger"
+	"github.com/pion/rtcp"
+)
+
+var _ bwe.BWE = (*SendSideBWE)(nil)
+
+//
+// Based on a simplified/modified version of JitterPath paper
+// (https://homepage.iis.sinica.edu.tw/papers/lcs/2114-F.pdf)
+//
+// TWCC feedback is used to calculate delta one-way-delay.
+// It is accumulated/propagated to determine in which region
+// groups of packets are operating in.
+//
+// In simplified terms,
+//   o JQR (Join Queuing Region) is when channel is congested.
+//   o DQR (Disjoint Queuing Region) is when channel is not.
+//
+// Packets are grouped and thresholds applied to smooth over
+// small variations. For example, in the paper,
+//    if propagated_queuing_delay + delta_one_way_delay > 0 {
+//       possibly_operating_in_jqr
+//    }
+// But, in this implementation it is checked at packet group level,
+// i. e. using queuing delay and aggregated delta one-way-delay of
+// the group and a minimum value threshold is applied before declaring
+// that a group is in JQR.
+//
+// There is also hysteresis to make transisitons smoother, i.e. if the
+// metric is above a certain threshold, it is JQR and it is DQR only if it
+// is below a certain value and the gap in between those two thresholds
+// are treated as interdeterminate groups.
+//
+
+// ---------------------------------------------------------------------------
+
+type SendSideBWEConfig struct {
+	CongestionDetector CongestionDetectorConfig `yaml:"congestion_detector,omitempty"`
+}
+
+var (
+	DefaultSendSideBWEConfig = SendSideBWEConfig{
+		CongestionDetector: defaultCongestionDetectorConfig,
+	}
+)
+
+// ---------------------------------------------------------------------------
+
+type SendSideBWEParams struct {
+	Config SendSideBWEConfig
+	Logger logger.Logger
+}
+
+type SendSideBWE struct {
+	bwe.NullBWE
+
+	params SendSideBWEParams
+
+	*congestionDetector
+}
+
+func NewSendSideBWE(params SendSideBWEParams) *SendSideBWE {
+	return &SendSideBWE{
+		params: params,
+		congestionDetector: newCongestionDetector(congestionDetectorParams{
+			Config: params.Config.CongestionDetector,
+			Logger: params.Logger,
+		}),
+	}
+}
+
+func (s *SendSideBWE) Type() bwe.BWEType {
+	return bwe.BWETypeSendSide
+}
+
+func (s *SendSideBWE) SetBWEListener(bweListener bwe.BWEListener) {
+	s.congestionDetector.SetBWEListener(bweListener)
+}
+
+func (s *SendSideBWE) Reset() {
+	s.congestionDetector.Reset()
+}
+
+func (s *SendSideBWE) RecordPacketSendAndGetSequenceNumber(
+	atMicro int64,
+	size int,
+	isRTX bool,
+	probeClusterId ccutils.ProbeClusterId,
+	isProbe bool,
+) uint16 {
+	return s.congestionDetector.RecordPacketSendAndGetSequenceNumber(atMicro, size, isRTX, probeClusterId, isProbe)
+}
+
+func (s *SendSideBWE) HandleTWCCFeedback(report *rtcp.TransportLayerCC) {
+	s.congestionDetector.HandleTWCCFeedback(report)
+}
+
+func (s *SendSideBWE) UpdateRTT(rtt float64) {
+	s.congestionDetector.UpdateRTT(rtt)
+}
+
+func (s *SendSideBWE) CongestionState() bwe.CongestionState {
+	return s.congestionDetector.CongestionState()
+}
+
+func (s *SendSideBWE) CanProbe() bool {
+	return s.congestionDetector.CanProbe()
+}
+
+func (s *SendSideBWE) ProbeDuration() time.Duration {
+	return s.congestionDetector.ProbeDuration()
+}
+
+func (s *SendSideBWE) ProbeClusterStarting(pci ccutils.ProbeClusterInfo) {
+	s.congestionDetector.ProbeClusterStarting(pci)
+}
+
+func (s *SendSideBWE) ProbeClusterDone(pci ccutils.ProbeClusterInfo) {
+	s.congestionDetector.ProbeClusterDone(pci)
+}
+
+func (s *SendSideBWE) ProbeClusterIsGoalReached() bool {
+	return s.congestionDetector.ProbeClusterIsGoalReached()
+}
+
+func (s *SendSideBWE) ProbeClusterFinalize() (ccutils.ProbeSignal, int64, bool) {
+	return s.congestionDetector.ProbeClusterFinalize()
+}
+
+// ------------------------------------------------