Preferr RRID for retransmission over RTX

rtptransceiver.go

@@ -95,12 +95,24 @@
 
 // match codecs from remote description, used when remote is offerer and creating a transceiver
 // from remote description with the aim of keeping order of codecs in remote description.
 func (t *RTPTransceiver) setCodecPreferencesFromRemoteDescription(media *sdp.MediaDescription) { //nolint:cyclop
 	remoteCodecs, err := codecsFromMediaDescription(media)
 	if err != nil {
 		return
 	}
 
+	simulcast := false
+	if len(getRids(media)) > 0 {
+		extensions, err := rtpExtensionsFromMediaDescription(media)
+		if err == nil {
+			for extension := range extensions {
+				if extension == sdp.SDESRepairRTPStreamIDURI {
+					simulcast = true
+				}
+			}
+		}
+	}
+
 	// make a copy as this slice is modified
 	leftCodecs := append([]RTPCodecParameters{}, t.api.mediaEngine.getCodecsByKind(t.kind)...)
 
@@ -172,6 +184,10 @@
 			continue
 		}
 
+		if simulcast {
+			continue
+		}
+
 		for _, rtxCodec := range leftCodecs {
 			if rtxCodec.PayloadType == mediaEngineRTX {
 				filteredCodecs = append(filteredCodecs, rtxCodec)