From 27bca60bb29d4cb7e8514d64937cd0e609ab4885 Mon Sep 17 00:00:00 2001
From: boks1971 <raja.gobi@tutanota.com>
Date: Sat, 16 Aug 2025 15:05:19 +0530
Subject: [PATCH] munges

---
 pkg/rtc/mediatracksubscriptions.go |  3 ++-
 pkg/rtc/participant.go             |  4 ++-
 pkg/rtc/participant_sdp.go         |  3 ++-
 pkg/rtc/transport.go               | 40 ++++++++++++++++++++++++++----
 4 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/pkg/rtc/mediatracksubscriptions.go b/pkg/rtc/mediatracksubscriptions.go
index 9026a5d84..9aef3c71a 100644
--- a/pkg/rtc/mediatracksubscriptions.go
+++ b/pkg/rtc/mediatracksubscriptions.go
@@ -16,6 +16,7 @@ package rtc
 
 import (
 	"errors"
+	"slices"
 	"sync"
 
 	"github.com/pion/rtcp"
@@ -311,7 +312,7 @@ func (t *MediaTrackSubscriptions) AddSubscriber(sub types.LocalParticipant, wr *
 	if transceiver == nil {
 		info := t.params.MediaTrack.ToProto()
 		addTrackParams := types.AddTrackParams{
-			Stereo: info.Stereo,
+			Stereo: slices.Contains(info.AudioFeatures, livekit.AudioTrackFeature_TF_STEREO),
 			Red:    !info.DisableRed,
 		}
 		if addTrackParams.Red && (len(codecs) == 1 && mime.IsMimeTypeStringOpus(codecs[0].MimeType)) {
diff --git a/pkg/rtc/participant.go b/pkg/rtc/participant.go
index bff2c3879..98f4441f9 100644
--- a/pkg/rtc/participant.go
+++ b/pkg/rtc/participant.go
@@ -2713,6 +2713,8 @@ func (p *ParticipantImpl) addPendingTrackLocked(req *livekit.AddTrackRequest) *l
 
 		track.(*MediaTrack).UpdateCodecInfo(req.SimulcastCodecs)
 		return track.ToProto()
+
+		// SINGLE-PEER-CONNECTION-TODO: AddRemoteTrack
 	}
 
 	backupCodecPolicy := req.BackupCodecPolicy
@@ -3792,7 +3794,7 @@ func (p *ParticipantImpl) UpdateAudioTrack(update *livekit.UpdateLocalAudioTrack
 			if ti.Sid == update.TrackSid {
 				isPending = true
 
-				ti.AudioFeatures = update.Features
+				ti.AudioFeatures = sutils.DedupeSlice(update.Features)
 				ti.Stereo = false
 				ti.DisableDtx = false
 				for _, feature := range update.Features {
diff --git a/pkg/rtc/participant_sdp.go b/pkg/rtc/participant_sdp.go
index d356ce7d8..3a0b9d027 100644
--- a/pkg/rtc/participant_sdp.go
+++ b/pkg/rtc/participant_sdp.go
@@ -16,6 +16,7 @@ package rtc
 
 import (
 	"fmt"
+	"slices"
 	"strconv"
 	"strings"
 
@@ -467,7 +468,7 @@ func (p *ParticipantImpl) configurePublisherAnswer(answer webrtc.SessionDescript
 					if !ti.DisableDtx {
 						attr.Value += ";usedtx=1"
 					}
-					if ti.Stereo {
+					if slices.Contains(ti.AudioFeatures, livekit.AudioTrackFeature_TF_STEREO) {
 						attr.Value += ";stereo=1;maxaveragebitrate=510000"
 					}
 					m.Attributes[i] = attr
diff --git a/pkg/rtc/transport.go b/pkg/rtc/transport.go
index d9b3494a5..a3bf91e68 100644
--- a/pkg/rtc/transport.go
+++ b/pkg/rtc/transport.go
@@ -935,7 +935,6 @@ func (t *PCTransport) AddTrack(trackLocal webrtc.TrackLocal, params types.AddTra
 		return
 	}
 
-	// as there is no way to get transceiver from sender, search
 	for _, tr := range t.pc.GetTransceivers() {
 		if tr.Sender() == sender {
 			transceiver = tr
@@ -1021,7 +1020,7 @@ func (t *PCTransport) AddRemoteTrackAndNegotiate(
 			}
 		}
 		if !disabled && !mime.IsMimeTypeStringRTX(c.RTPCodecCapability.MimeType) {
-			// SINGLE-PEER-CONNECTION-TOOD: remove `nack` for RED and add `nack` for Opus
+			// SINGLE-PEER-CONNECTION-TOOD: remove `nack` for RED?
 			if rtpCodecType == webrtc.RTPCodecTypeVideo {
 				c.RTPCodecCapability.RTCPFeedback = rtcpFeedbackConfig.Video
 			} else {
@@ -1082,9 +1081,40 @@ func (t *PCTransport) AddRemoteTrackAndNegotiate(
 			leftCodecs = append(leftCodecs, enabledCodec)
 		}
 	}
-	transceiver.SetCodecPreferences(append(append([]webrtc.RTPCodecParameters{}, preferredCodecs...), leftCodecs...))
-	// SINGLE-PEER-CONNECTION-TOOD: need to configure stereo for audio codecs
-	// SINGLE-PEER-CONNECTION-TODO: do setCodecPreferencesOpusRedForPublisher for audio
+
+	enabledCodecs = append(append([]webrtc.RTPCodecParameters{}, preferredCodecs...), leftCodecs...)
+
+	// enable dtx, stereo for Opus
+	opusPayload := webrtc.PayloadType(0)
+	for _, enabledCodec := range enabledCodecs {
+		if mime.IsMimeTypeStringOpus(enabledCodec.RTPCodecCapability.MimeType) {
+			opusPayload = enabledCodec.PayloadType
+			if !ti.DisableDtx {
+				enabledCodec.RTPCodecCapability.SDPFmtpLine += ";usedtx=1"
+			}
+			if slices.Contains(ti.AudioFeatures, livekit.AudioTrackFeature_TF_STEREO) {
+				enabledCodec.RTPCodecCapability.SDPFmtpLine += ";stereo=1;maxaveragebitrate=510000"
+			}
+			break
+		}
+	}
+
+	// prioritize audio/red if not disabled and available
+	if opusPayload != 0 {
+		preferredCodecs = nil
+		leftCodecs = nil
+		for _, enabledCodec := range enabledCodecs {
+			if !ti.DisableRed && mime.IsMimeTypeStringRED(enabledCodec.RTPCodecCapability.MimeType) && strings.Contains(enabledCodec.RTPCodecCapability.SDPFmtpLine, strconv.FormatInt(int64(opusPayload), 10)) {
+				preferredCodecs = append(preferredCodecs, enabledCodec)
+			} else {
+				leftCodecs = append(leftCodecs, enabledCodec)
+			}
+		}
+
+		enabledCodecs = append(append([]webrtc.RTPCodecParameters{}, preferredCodecs...), leftCodecs...)
+	}
+
+	transceiver.SetCodecPreferences(enabledCodecs)
 
 	t.Negotiate(true)
 	return nil