Do not send both asb-send-time and twcc. (#3890)

* Do not send both asb-send-time and twcc.

In single peer connection mode, both extensions are set on the media
engine and both would be negotiated. Unfortunately, pion/webrtc does
not yet support RTPSender.SetParameters() which would allow setting
specific header extensions for the sender. So, check for TWCC enabled
and use it. If not, do abs-send-time if that is enabled.

* check BWE type

* comment

pkg/rtc/mediaengine.go

@@ -286,7 +286,6 @@ func filterCodecs(
 
 		for _, enabledCodec := range enabledCodecs {
 			if mime.NormalizeMimeType(enabledCodec.Mime) == mime.NormalizeMimeType(c.RTPCodecCapability.MimeType) {
-				// SINGLE-PEER-CONNECTION-TOOD: remove `nack` for RED?
 				if mime.IsMimeTypeStringVideo(c.RTPCodecCapability.MimeType) {
 					c.RTPCodecCapability.RTCPFeedback = rtcpFeedbackConfig.Video
 				} else {

pkg/rtc/transport.go

@@ -424,7 +424,8 @@ func newPeerConnection(params TransportParams, onBandwidthEstimator func(estimat
 				}
 			}
 		}
-	} else {
+	}
+	if !params.IsOfferer {
 		// sfu only use interceptor to send XR but don't read response from it (use buffer instead),
 		// so use a empty callback here
 		ir.Add(lkinterceptor.NewRTTFromXRFactory(func(rtt uint32) {}))

pkg/sfu/bwe/bwe.go

@@ -31,6 +31,29 @@ const (
 
 // ------------------------------------------------
 
+type BWEType int
+
+const (
+	BWETypeNone BWEType = iota
+	BWETypeRemote
+	BWETypeSendSide
+)
+
+func (b BWEType) String() string {
+	switch b {
+	case BWETypeNone:
+		return "NONE"
+	case BWETypeRemote:
+		return "REMOTE"
+	case BWETypeSendSide:
+		return "SEND_SIDE"
+	default:
+		return fmt.Sprintf("%d", int(b))
+	}
+}
+
+// ------------------------------------------------
+
 type CongestionState int
 
 const (
@@ -55,6 +78,8 @@ func (c CongestionState) String() string {
 // ------------------------------------------------
 
 type BWE interface {
+	Type() BWEType
+
 	SetBWEListener(bweListner BWEListener)
 
 	Reset()

pkg/sfu/bwe/remotebwe/remote_bwe.go

@@ -24,6 +24,8 @@ import (
 	"github.com/livekit/protocol/utils/mono"
 )
 
+var _ bwe.BWE = (*RemoteBWE)(nil)
+
 // ---------------------------------------------------------------------------
 
 type RemoteBWEConfig struct {
@@ -81,6 +83,10 @@ func NewRemoteBWE(params RemoteBWEParams) *RemoteBWE {
 	return r
 }
 
+func (r *RemoteBWE) Type() bwe.BWEType {
+	return bwe.BWETypeRemote
+}
+
 func (r *RemoteBWE) SetBWEListener(bweListener bwe.BWEListener) {
 	r.lock.Lock()
 	defer r.lock.Unlock()

pkg/sfu/bwe/sendsidebwe/send_side_bwe.go

@@ -23,6 +23,8 @@ import (
 	"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)
@@ -88,6 +90,10 @@ func NewSendSideBWE(params SendSideBWEParams) *SendSideBWE {
 	}
 }
 
+func (r *SendSideBWE) Type() bwe.BWEType {
+	return bwe.BWETypeSendSide
+}
+
 func (s *SendSideBWE) SetBWEListener(bweListener bwe.BWEListener) {
 	s.congestionDetector.SetBWEListener(bweListener)
 }

pkg/sfu/downtrack.go

@@ -38,6 +38,7 @@ import (
 	"github.com/livekit/protocol/utils/mono"
 
 	"github.com/livekit/livekit-server/pkg/sfu/buffer"
+	"github.com/livekit/livekit-server/pkg/sfu/bwe"
 	"github.com/livekit/livekit-server/pkg/sfu/ccutils"
 	"github.com/livekit/livekit-server/pkg/sfu/connectionquality"
 	"github.com/livekit/livekit-server/pkg/sfu/mime"
@@ -192,6 +193,9 @@ type DownTrackStreamAllocatorListener interface {
 	// check if track should participate in BWE
 	IsBWEEnabled(dt *DownTrack) bool
 
+	// get the BWE type in use
+	BWEType() bwe.BWEType
+
 	// check if subscription mute can be applied
 	IsSubscribeMutable(dt *DownTrack) bool
 }
@@ -793,13 +797,15 @@ func (d *DownTrack) SetReceiver(r TrackReceiver) {
 // Sets RTP header extensions for this track
 func (d *DownTrack) SetRTPHeaderExtensions(rtpHeaderExtensions []webrtc.RTPHeaderExtensionParameter) {
 	isBWEEnabled := true
+	bweType := bwe.BWETypeNone
 	if sal := d.getStreamAllocatorListener(); sal != nil {
 		isBWEEnabled = sal.IsBWEEnabled(d)
+		bweType = sal.BWEType()
 	}
 	for _, ext := range rtpHeaderExtensions {
 		switch ext.URI {
 		case sdp.ABSSendTimeURI:
-			if isBWEEnabled {
+			if isBWEEnabled && bweType == bwe.BWETypeRemote {
 				d.absSendTimeExtID = ext.ID
 			} else {
 				d.absSendTimeExtID = 0
@@ -809,7 +815,7 @@ func (d *DownTrack) SetRTPHeaderExtensions(rtpHeaderExtensions []webrtc.RTPHeade
 		case pd.PlayoutDelayURI:
 			d.playoutDelayExtID = ext.ID
 		case sdp.TransportCCURI:
-			if isBWEEnabled {
+			if isBWEEnabled && bweType == bwe.BWETypeSendSide {
 				d.transportWideExtID = ext.ID
 			} else {
 				d.transportWideExtID = 0

pkg/sfu/streamallocator/streamallocator.go

@@ -557,6 +557,10 @@ func (s *StreamAllocator) IsBWEEnabled(downTrack *sfu.DownTrack) bool {
 	return true
 }
 
+func (s *StreamAllocator) BWEType() bwe.BWEType {
+	return s.params.BWE.Type()
+}
+
 // called to check if track subscription mute can be applied
 func (s *StreamAllocator) IsSubscribeMutable(downTrack *sfu.DownTrack) bool {
 	s.videoTracksMu.Lock()