Provide correct StreamInfo to receiver interceptors

Author: 3DRX

rtpcodec.go

@@ -143,16 +143,26 @@ func codecParametersFuzzySearch(
 	return RTPCodecParameters{}, codecMatchNone
 }
 
-// Given a CodecParameters find the RTX CodecParameters if one exists.
+// Given a CodecParameters find the RTX PayloadType.
 func findRTXPayloadType(needle PayloadType, haystack []RTPCodecParameters) PayloadType {
+	rtxParam := findRTXCodecParameters(needle, haystack)
+	if rtxParam != nil {
+		return rtxParam.PayloadType
+	}
+
+	return PayloadType(0)
+}
+
+// Given a CodecParameters find the RTX CodecParameters if one exists.
+func findRTXCodecParameters(needle PayloadType, haystack []RTPCodecParameters) *RTPCodecParameters {
 	aptStr := fmt.Sprintf("apt=%d", needle)
-	for _, c := range haystack {
+	for i, c := range haystack {
 		if aptStr == c.SDPFmtpLine {
-			return c.PayloadType
+			return &haystack[i]
 		}
 	}
 
-	return PayloadType(0)
+	return nil
 }
 
 // For now, only FlexFEC is supported.

rtpreceiver.go

@@ -218,10 +218,20 @@ func (r *RTPReceiver) startReceive(parameters RTPReceiveParameters) error { //no
 			return fmt.Errorf("%w: %d", errRTPReceiverWithSSRCTrackStreamNotFound, parameters.Encodings[i].SSRC)
 		}
 
+		rtxPayloadType := PayloadType(0)
+		rtxParam := findRTXCodecParameters(globalParams.Codecs[0].PayloadType, globalParams.Codecs)
+		if rtxParam != nil {
+			rtxPayloadType = rtxParam.PayloadType
+		}
+
 		streams.streamInfo = createStreamInfo(
 			"",
 			parameters.Encodings[i].SSRC,
-			0, 0, 0, 0, 0,
+			parameters.Encodings[i].RTX.SSRC,
+			parameters.Encodings[i].FEC.SSRC,
+			globalParams.Codecs[0].PayloadType,
+			rtxPayloadType,
+			findFECPayloadType(globalParams.Codecs),
 			codec,
 			globalParams.HeaderExtensions,
 		)
@@ -233,7 +243,17 @@ func (r *RTPReceiver) startReceive(parameters RTPReceiveParameters) error { //no
 		}
 
 		if rtxSsrc := parameters.Encodings[i].RTX.SSRC; rtxSsrc != 0 {
-			streamInfo := createStreamInfo("", rtxSsrc, 0, 0, 0, 0, 0, codec, globalParams.HeaderExtensions)
+			streamInfo := createStreamInfo(
+				"",
+				rtxSsrc,
+				0,
+				0,
+				rtxPayloadType,
+				0,
+				0,
+				rtxParam.RTPCodecCapability,
+				globalParams.HeaderExtensions,
+			)
 			rtpReadStream, rtpInterceptor, rtcpReadStream, rtcpInterceptor, err := r.transport.streamsForSSRC(
 				rtxSsrc,
 				*streamInfo,