diff --git a/examples/server-tls/main.go b/examples/server-tls/main.go
index 8b2cf3e6..5271bbd7 100644
--- a/examples/server-tls/main.go
+++ b/examples/server-tls/main.go
@@ -93,12 +93,12 @@ func (sh *serverHandler) OnAnnounce(ctx *gortsplib.ServerHandlerOnAnnounceCtx) (
 }
 
 // called after receiving a SETUP request.
-func (sh *serverHandler) OnSetup(ctx *gortsplib.ServerHandlerOnSetupCtx) (*base.Response, error) {
+func (sh *serverHandler) OnSetup(ctx *gortsplib.ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 	log.Printf("setup request")
 
 	return &base.Response{
 		StatusCode: base.StatusOK,
-	}, nil
+	}, nil, nil
 }
 
 // called after receiving a PLAY request.
diff --git a/examples/server/main.go b/examples/server/main.go
index b14b03cd..e5990101 100644
--- a/examples/server/main.go
+++ b/examples/server/main.go
@@ -92,12 +92,12 @@ func (sh *serverHandler) OnAnnounce(ctx *gortsplib.ServerHandlerOnAnnounceCtx) (
 }
 
 // called after receiving a SETUP request.
-func (sh *serverHandler) OnSetup(ctx *gortsplib.ServerHandlerOnSetupCtx) (*base.Response, error) {
+func (sh *serverHandler) OnSetup(ctx *gortsplib.ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 	log.Printf("setup request")
 
 	return &base.Response{
 		StatusCode: base.StatusOK,
-	}, nil
+	}, nil, nil
 }
 
 // called after receiving a PLAY request.
diff --git a/server_publish_test.go b/server_publish_test.go
index 8d53bd04..b7178740 100644
--- a/server_publish_test.go
+++ b/server_publish_test.go
@@ -301,12 +301,12 @@ func TestServerPublishSetupPath(t *testing.T) {
 							StatusCode: base.StatusOK,
 						}, nil
 					},
-					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 						require.Equal(t, ca.path, ctx.Path)
 						require.Equal(t, ca.trackID, ctx.TrackID)
 						return &base.Response{
 							StatusCode: base.StatusOK,
-						}, nil
+						}, nil, nil
 					},
 				},
 			}
@@ -398,10 +398,10 @@ func TestServerPublishErrorSetupDifferentPaths(t *testing.T) {
 					StatusCode: base.StatusOK,
 				}, nil
 			},
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 		},
 	}
@@ -480,10 +480,10 @@ func TestServerPublishErrorSetupTrackTwice(t *testing.T) {
 					StatusCode: base.StatusOK,
 				}, nil
 			},
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 		},
 	}
@@ -574,10 +574,10 @@ func TestServerPublishErrorRecordPartialTracks(t *testing.T) {
 					StatusCode: base.StatusOK,
 				}, nil
 			},
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 			onRecord: func(ctx *ServerHandlerOnRecordCtx) (*base.Response, error) {
 				return &base.Response{
@@ -694,10 +694,10 @@ func TestServerPublish(t *testing.T) {
 							StatusCode: base.StatusOK,
 						}, nil
 					},
-					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 						return &base.Response{
 							StatusCode: base.StatusOK,
-						}, nil
+						}, nil, nil
 					},
 					onRecord: func(ctx *ServerHandlerOnRecordCtx) (*base.Response, error) {
 						return &base.Response{
@@ -912,10 +912,10 @@ func TestServerPublishErrorWrongProtocol(t *testing.T) {
 					StatusCode: base.StatusOK,
 				}, nil
 			},
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 			onRecord: func(ctx *ServerHandlerOnRecordCtx) (*base.Response, error) {
 				return &base.Response{
@@ -1018,10 +1018,10 @@ func TestServerPublishRTCPReport(t *testing.T) {
 					StatusCode: base.StatusOK,
 				}, nil
 			},
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 			onRecord: func(ctx *ServerHandlerOnRecordCtx) (*base.Response, error) {
 				return &base.Response{
@@ -1174,10 +1174,10 @@ func TestServerPublishTimeout(t *testing.T) {
 							StatusCode: base.StatusOK,
 						}, nil
 					},
-					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 						return &base.Response{
 							StatusCode: base.StatusOK,
-						}, nil
+						}, nil, nil
 					},
 					onRecord: func(ctx *ServerHandlerOnRecordCtx) (*base.Response, error) {
 						return &base.Response{
@@ -1302,10 +1302,10 @@ func TestServerPublishWithoutTeardown(t *testing.T) {
 							StatusCode: base.StatusOK,
 						}, nil
 					},
-					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 						return &base.Response{
 							StatusCode: base.StatusOK,
-						}, nil
+						}, nil, nil
 					},
 					onRecord: func(ctx *ServerHandlerOnRecordCtx) (*base.Response, error) {
 						return &base.Response{
@@ -1414,10 +1414,10 @@ func TestServerPublishUDPChangeConn(t *testing.T) {
 					StatusCode: base.StatusOK,
 				}, nil
 			},
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 			onRecord: func(ctx *ServerHandlerOnRecordCtx) (*base.Response, error) {
 				return &base.Response{
diff --git a/server_read_test.go b/server_read_test.go
index 1681f8a2..be626024 100644
--- a/server_read_test.go
+++ b/server_read_test.go
@@ -61,12 +61,12 @@ func TestServerReadSetupPath(t *testing.T) {
 		t.Run(ca.name, func(t *testing.T) {
 			s := &Server{
 				Handler: &testServerHandler{
-					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 						require.Equal(t, ca.path, ctx.Path)
 						require.Equal(t, ca.trackID, ctx.TrackID)
 						return &base.Response{
 							StatusCode: base.StatusOK,
-						}, nil
+						}, nil, nil
 					},
 				},
 			}
@@ -116,10 +116,10 @@ func TestServerReadErrorSetupDifferentPaths(t *testing.T) {
 				require.Equal(t, "can't setup tracks with different paths", ctx.Error.Error())
 				close(connClosed)
 			},
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 		},
 	}
@@ -183,10 +183,10 @@ func TestServerReadErrorSetupTrackTwice(t *testing.T) {
 				require.Equal(t, "track 0 has already been setup", ctx.Error.Error())
 				close(connClosed)
 			},
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 		},
 	}
@@ -268,10 +268,11 @@ func TestServerRead(t *testing.T) {
 					onSessionClose: func(ctx *ServerHandlerOnSessionCloseCtx) {
 						close(sessionClosed)
 					},
-					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
+						v := uint32(123456)
 						return &base.Response{
 							StatusCode: base.StatusOK,
-						}, nil
+						}, &v, nil
 					},
 					onPlay: func(ctx *ServerHandlerOnPlayCtx) (*base.Response, error) {
 						ctx.Session.WriteFrame(0, StreamTypeRTP, []byte{0x01, 0x02, 0x03, 0x04})
@@ -356,6 +357,7 @@ func TestServerRead(t *testing.T) {
 			var th headers.Transport
 			err = th.Read(res.Header["Transport"])
 			require.NoError(t, err)
+			require.Equal(t, uint32(123456), *th.SSRC)
 
 			<-sessionOpened
 
@@ -483,10 +485,10 @@ func TestServerReadTCPResponseBeforeFrames(t *testing.T) {
 				close(writerTerminate)
 				<-writerDone
 			},
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 			onPlay: func(ctx *ServerHandlerOnPlayCtx) (*base.Response, error) {
 				go func() {
@@ -567,10 +569,10 @@ func TestServerReadTCPResponseBeforeFrames(t *testing.T) {
 func TestServerReadPlayPlay(t *testing.T) {
 	s := &Server{
 		Handler: &testServerHandler{
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 			onPlay: func(ctx *ServerHandlerOnPlayCtx) (*base.Response, error) {
 				return &base.Response{
@@ -647,10 +649,10 @@ func TestServerReadPlayPausePlay(t *testing.T) {
 				close(writerTerminate)
 				<-writerDone
 			},
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 			onPlay: func(ctx *ServerHandlerOnPlayCtx) (*base.Response, error) {
 				if !writerStarted {
@@ -759,10 +761,10 @@ func TestServerReadPlayPausePause(t *testing.T) {
 				close(writerTerminate)
 				<-writerDone
 			},
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 			onPlay: func(ctx *ServerHandlerOnPlayCtx) (*base.Response, error) {
 				go func() {
@@ -882,10 +884,10 @@ func TestServerReadTimeout(t *testing.T) {
 							StatusCode: base.StatusOK,
 						}, nil
 					},
-					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 						return &base.Response{
 							StatusCode: base.StatusOK,
-						}, nil
+						}, nil, nil
 					},
 					onPlay: func(ctx *ServerHandlerOnPlayCtx) (*base.Response, error) {
 						return &base.Response{
@@ -972,10 +974,10 @@ func TestServerReadWithoutTeardown(t *testing.T) {
 							StatusCode: base.StatusOK,
 						}, nil
 					},
-					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 						return &base.Response{
 							StatusCode: base.StatusOK,
-						}, nil
+						}, nil, nil
 					},
 					onPlay: func(ctx *ServerHandlerOnPlayCtx) (*base.Response, error) {
 						return &base.Response{
@@ -1053,10 +1055,10 @@ func TestServerReadWithoutTeardown(t *testing.T) {
 func TestServerReadUDPChangeConn(t *testing.T) {
 	s := &Server{
 		Handler: &testServerHandler{
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 			onPlay: func(ctx *ServerHandlerOnPlayCtx) (*base.Response, error) {
 				return &base.Response{
diff --git a/server_test.go b/server_test.go
index d1ce5305..8c02c5df 100644
--- a/server_test.go
+++ b/server_test.go
@@ -44,7 +44,7 @@ type testServerHandler struct {
 	onSessionClose func(*ServerHandlerOnSessionCloseCtx)
 	onDescribe     func(*ServerHandlerOnDescribeCtx) (*base.Response, []byte, error)
 	onAnnounce     func(*ServerHandlerOnAnnounceCtx) (*base.Response, error)
-	onSetup        func(*ServerHandlerOnSetupCtx) (*base.Response, error)
+	onSetup        func(*ServerHandlerOnSetupCtx) (*base.Response, *uint32, error)
 	onPlay         func(*ServerHandlerOnPlayCtx) (*base.Response, error)
 	onRecord       func(*ServerHandlerOnRecordCtx) (*base.Response, error)
 	onPause        func(*ServerHandlerOnPauseCtx) (*base.Response, error)
@@ -91,11 +91,11 @@ func (sh *testServerHandler) OnAnnounce(ctx *ServerHandlerOnAnnounceCtx) (*base.
 	return nil, fmt.Errorf("unimplemented")
 }
 
-func (sh *testServerHandler) OnSetup(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+func (sh *testServerHandler) OnSetup(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 	if sh.onSetup != nil {
 		return sh.onSetup(ctx)
 	}
-	return nil, fmt.Errorf("unimplemented")
+	return nil, nil, fmt.Errorf("unimplemented")
 }
 
 func (sh *testServerHandler) OnPlay(ctx *ServerHandlerOnPlayCtx) (*base.Response, error) {
@@ -327,11 +327,11 @@ func TestServerHighLevelPublishRead(t *testing.T) {
 							},
 						}, nil
 					},
-					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 						if ctx.Path != "teststream" {
 							return &base.Response{
 								StatusCode: base.StatusBadRequest,
-							}, fmt.Errorf("invalid path (%s)", ctx.Req.URL)
+							}, nil, fmt.Errorf("invalid path (%s)", ctx.Req.URL)
 						}
 
 						return &base.Response{
@@ -339,7 +339,7 @@ func TestServerHighLevelPublishRead(t *testing.T) {
 							Header: base.Header{
 								"Session": base.HeaderValue{"12345678"},
 							},
-						}, nil
+						}, nil, nil
 					},
 					onPlay: func(ctx *ServerHandlerOnPlayCtx) (*base.Response, error) {
 						if ctx.Path != "teststream" {
@@ -620,10 +620,10 @@ func TestServerErrorInvalidMethod(t *testing.T) {
 func TestServerErrorTCPTwoConnOneSession(t *testing.T) {
 	s := &Server{
 		Handler: &testServerHandler{
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 			onPlay: func(ctx *ServerHandlerOnPlayCtx) (*base.Response, error) {
 				return &base.Response{
@@ -712,10 +712,10 @@ func TestServerErrorTCPTwoConnOneSession(t *testing.T) {
 func TestServerErrorTCPOneConnTwoSessions(t *testing.T) {
 	s := &Server{
 		Handler: &testServerHandler{
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 			onPlay: func(ctx *ServerHandlerOnPlayCtx) (*base.Response, error) {
 				return &base.Response{
@@ -920,10 +920,10 @@ func TestServerSessionClose(t *testing.T) {
 			onSessionClose: func(ctx *ServerHandlerOnSessionCloseCtx) {
 				close(sessionClosed)
 			},
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 		},
 	}
@@ -969,10 +969,10 @@ func TestServerSessionAutoClose(t *testing.T) {
 			onSessionClose: func(ctx *ServerHandlerOnSessionCloseCtx) {
 				close(sessionClosed)
 			},
-			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+			onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 				return &base.Response{
 					StatusCode: base.StatusOK,
-				}, nil
+				}, nil, nil
 			},
 		},
 	}
@@ -1036,10 +1036,10 @@ func TestServerErrorInvalidPath(t *testing.T) {
 							StatusCode: base.StatusOK,
 						}, nil
 					},
-					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, error) {
+					onSetup: func(ctx *ServerHandlerOnSetupCtx) (*base.Response, *uint32, error) {
 						return &base.Response{
 							StatusCode: base.StatusOK,
-						}, nil
+						}, nil, nil
 					},
 					onPlay: func(ctx *ServerHandlerOnPlayCtx) (*base.Response, error) {
 						return &base.Response{
diff --git a/serverhandler.go b/serverhandler.go
index 2825cc0b..473d8355 100644
--- a/serverhandler.go
+++ b/serverhandler.go
@@ -103,7 +103,9 @@ type ServerHandlerOnSetupCtx struct {
 
 // ServerHandlerOnSetup can be implemented by a ServerHandler.
 type ServerHandlerOnSetup interface {
-	OnSetup(*ServerHandlerOnSetupCtx) (*base.Response, error)
+	// returns a Response and an optional SSRC that is
+	// inserted into the Transport header.
+	OnSetup(*ServerHandlerOnSetupCtx) (*base.Response, *uint32, error)
 }
 
 // ServerHandlerOnPlayCtx is the context of a PLAY request.
diff --git a/serversession.go b/serversession.go
index 9f47a61e..6eeb506f 100644
--- a/serversession.go
+++ b/serversession.go
@@ -503,21 +503,21 @@ func (ss *ServerSession) handleRequest(sc *ServerConn, req *base.Request) (*base
 			}, err
 		}
 
-		var th headers.Transport
-		err = th.Read(req.Header["Transport"])
+		var inTH headers.Transport
+		err = inTH.Read(req.Header["Transport"])
 		if err != nil {
 			return &base.Response{
 				StatusCode: base.StatusBadRequest,
 			}, liberrors.ErrServerTransportHeaderInvalid{Err: err}
 		}
 
-		if th.Delivery != nil && *th.Delivery == base.StreamDeliveryMulticast {
+		if inTH.Delivery != nil && *inTH.Delivery == base.StreamDeliveryMulticast {
 			return &base.Response{
 				StatusCode: base.StatusUnsupportedTransport,
 			}, nil
 		}
 
-		trackID, path, query, err := setupGetTrackIDPathQuery(req.URL, th.Mode,
+		trackID, path, query, err := setupGetTrackIDPathQuery(req.URL, inTH.Mode,
 			ss.announcedTracks, ss.setupPath, ss.setupQuery)
 		if err != nil {
 			return &base.Response{
@@ -533,67 +533,67 @@ func (ss *ServerSession) handleRequest(sc *ServerConn, req *base.Request) (*base
 
 		switch ss.state {
 		case ServerSessionStateInitial, ServerSessionStatePrePlay: // play
-			if th.Mode != nil && *th.Mode != headers.TransportModePlay {
+			if inTH.Mode != nil && *inTH.Mode != headers.TransportModePlay {
 				return &base.Response{
 					StatusCode: base.StatusBadRequest,
-				}, liberrors.ErrServerTransportHeaderWrongMode{Mode: th.Mode}
+				}, liberrors.ErrServerTransportHeaderWrongMode{Mode: inTH.Mode}
 			}
 
 		default: // record
-			if th.Mode == nil || *th.Mode != headers.TransportModeRecord {
+			if inTH.Mode == nil || *inTH.Mode != headers.TransportModeRecord {
 				return &base.Response{
 					StatusCode: base.StatusBadRequest,
-				}, liberrors.ErrServerTransportHeaderWrongMode{Mode: th.Mode}
+				}, liberrors.ErrServerTransportHeaderWrongMode{Mode: inTH.Mode}
 			}
 		}
 
-		if th.Protocol == StreamProtocolUDP {
+		if inTH.Protocol == StreamProtocolUDP {
 			if ss.s.udpRTPListener == nil {
 				return &base.Response{
 					StatusCode: base.StatusUnsupportedTransport,
 				}, nil
 			}
 
-			if th.ClientPorts == nil {
+			if inTH.ClientPorts == nil {
 				return &base.Response{
 					StatusCode: base.StatusBadRequest,
 				}, liberrors.ErrServerTransportHeaderNoClientPorts{}
 			}
 
 		} else {
-			if th.InterleavedIDs == nil {
+			if inTH.InterleavedIDs == nil {
 				return &base.Response{
 					StatusCode: base.StatusBadRequest,
 				}, liberrors.ErrServerTransportHeaderNoInterleavedIDs{}
 			}
 
-			if th.InterleavedIDs[0] != (trackID*2) ||
-				th.InterleavedIDs[1] != (1+trackID*2) {
+			if inTH.InterleavedIDs[0] != (trackID*2) ||
+				inTH.InterleavedIDs[1] != (1+trackID*2) {
 				return &base.Response{
 						StatusCode: base.StatusBadRequest,
 					}, liberrors.ErrServerTransportHeaderWrongInterleavedIDs{
-						Expected: [2]int{(trackID * 2), (1 + trackID*2)}, Value: *th.InterleavedIDs}
+						Expected: [2]int{(trackID * 2), (1 + trackID*2)}, Value: *inTH.InterleavedIDs}
 			}
 		}
 
-		if ss.setupProtocol != nil && *ss.setupProtocol != th.Protocol {
+		if ss.setupProtocol != nil && *ss.setupProtocol != inTH.Protocol {
 			return &base.Response{
 				StatusCode: base.StatusBadRequest,
 			}, liberrors.ErrServerTracksDifferentProtocols{}
 		}
 
-		res, err := ss.s.Handler.(ServerHandlerOnSetup).OnSetup(&ServerHandlerOnSetupCtx{
+		res, ssrc, err := ss.s.Handler.(ServerHandlerOnSetup).OnSetup(&ServerHandlerOnSetupCtx{
 			Session:   ss,
 			Conn:      sc,
 			Req:       req,
 			Path:      path,
 			Query:     query,
 			TrackID:   trackID,
-			Transport: &th,
+			Transport: &inTH,
 		})
 
 		if res.StatusCode == base.StatusOK {
-			ss.setupProtocol = &th.Protocol
+			ss.setupProtocol = &inTH.Protocol
 
 			if ss.setuppedTracks == nil {
 				ss.setuppedTracks = make(map[int]ServerSessionSetuppedTrack)
@@ -603,30 +603,35 @@ func (ss *ServerSession) handleRequest(sc *ServerConn, req *base.Request) (*base
 				res.Header = make(base.Header)
 			}
 
-			if th.Protocol == StreamProtocolUDP {
+			th := headers.Transport{
+				Delivery: func() *base.StreamDelivery {
+					v := base.StreamDeliveryUnicast
+					return &v
+				}(),
+			}
+
+			if inTH.Protocol == StreamProtocolUDP {
 				ss.setuppedTracks[trackID] = ServerSessionSetuppedTrack{
-					udpRTPPort:  th.ClientPorts[0],
-					udpRTCPPort: th.ClientPorts[1],
+					udpRTPPort:  inTH.ClientPorts[0],
+					udpRTCPPort: inTH.ClientPorts[1],
 				}
 
-				res.Header["Transport"] = headers.Transport{
-					Protocol: StreamProtocolUDP,
-					Delivery: func() *base.StreamDelivery {
-						v := base.StreamDeliveryUnicast
-						return &v
-					}(),
-					ClientPorts: th.ClientPorts,
-					ServerPorts: &[2]int{sc.s.udpRTPListener.port(), sc.s.udpRTCPListener.port()},
-				}.Write()
+				th.Protocol = StreamProtocolUDP
+				th.ClientPorts = inTH.ClientPorts
+				th.ServerPorts = &[2]int{sc.s.udpRTPListener.port(), sc.s.udpRTCPListener.port()}
 
 			} else {
 				ss.setuppedTracks[trackID] = ServerSessionSetuppedTrack{}
 
-				res.Header["Transport"] = headers.Transport{
-					Protocol:       StreamProtocolTCP,
-					InterleavedIDs: th.InterleavedIDs,
-				}.Write()
+				th.Protocol = StreamProtocolTCP
+				th.InterleavedIDs = inTH.InterleavedIDs
 			}
+
+			if ssrc != nil {
+				th.SSRC = ssrc
+			}
+
+			res.Header["Transport"] = th.Write()
 		}
 
 		if ss.state == ServerSessionStateInitial {