diff --git a/client.go b/client.go
index a9252b33..bc9f43f2 100644
--- a/client.go
+++ b/client.go
@@ -41,6 +41,47 @@ const (
 	clientUserAgent = "gortsplib"
 )
 
+func generateLocalSSRCs(existing []uint32, formats []format.Format) (map[uint8]uint32, error) {
+	ret := make(map[uint8]uint32)
+
+	for _, forma := range formats {
+		for {
+			ssrc, err := randUint32()
+			if err != nil {
+				return nil, err
+			}
+
+			if ssrc != 0 && !slices.Contains(existing, ssrc) {
+				existing = append(existing, ssrc)
+				ret[forma.PayloadType()] = ssrc
+				break
+			}
+		}
+	}
+
+	return ret, nil
+}
+
+func ssrcsMapToList(m map[uint8]uint32) []uint32 {
+	ret := make([]uint32, len(m))
+	n := 0
+	for _, el := range m {
+		ret[n] = el
+		n++
+	}
+	return ret
+}
+
+func clientExtractExistingSSRCs(setuppedMedias map[*description.Media]*clientMedia) []uint32 {
+	var ret []uint32
+	for _, media := range setuppedMedias {
+		for _, forma := range media.formats {
+			ret = append(ret, forma.localSSRC)
+		}
+	}
+	return ret
+}
+
 // avoid an int64 overflow and preserve resolution by splitting division into two parts:
 // first add the integer part, then the decimal part.
 func multiplyAndDivide(v, m, d time.Duration) time.Duration {
@@ -134,16 +175,16 @@ func announceDataPickLocalSSRC(
 	am *clientAnnounceDataMedia,
 	data map[*description.Media]*clientAnnounceDataMedia,
 ) (uint32, error) {
-	var takenSSRCs []uint32 //nolint:prealloc
+	var existing []uint32 //nolint:prealloc
 
 	for _, am := range data {
 		for _, af := range am.formats {
-			takenSSRCs = append(takenSSRCs, af.localSSRC)
+			existing = append(existing, af.localSSRC)
 		}
 	}
 
 	for _, af := range am.formats {
-		takenSSRCs = append(takenSSRCs, af.localSSRC)
+		existing = append(existing, af.localSSRC)
 	}
 
 	for {
@@ -152,7 +193,7 @@ func announceDataPickLocalSSRC(
 			return 0, err
 		}
 
-		if ssrc != 0 && !slices.Contains(takenSSRCs, ssrc) {
+		if ssrc != 0 && !slices.Contains(existing, ssrc) {
 			return ssrc, nil
 		}
 	}
@@ -214,9 +255,9 @@ func prepareForAnnounce(
 				n++
 			}
 
-			// use a dummy Context.
+			// create a temporary Context.
 			// Context is needed to extract ROC, but since client has not started streaming,
-			// ROC is always zero, therefore a dummy Context can be used.
+			// ROC is always zero, therefore a temporary Context can be used.
 			srtpCtx := &wrappedSRTPContext{
 				key:   announceDataMedia.srtpOutKey,
 				ssrcs: ssrcs,
@@ -527,8 +568,8 @@ type Client struct {
 	keepAlivePeriod      time.Duration
 	keepAliveTimer       *time.Timer
 	closeError           error
-	writer               *asyncProcessor
 	writerMutex          sync.RWMutex
+	writer               *asyncProcessor
 	reader               *clientReader
 	timeDecoder          *rtptime.GlobalDecoder2
 	mustClose            bool
@@ -1618,20 +1659,41 @@ func (c *Client) doSetup(
 		}
 	}
 
-	cm := &clientMedia{
-		c:      c,
-		media:  medi,
-		secure: isSecure(th.Profile),
-	}
-	err = cm.initialize()
-	if err != nil {
-		return nil, err
+	var localSSRCs map[uint8]uint32
+
+	if c.state == clientStatePreRecord {
+		localSSRCs = make(map[uint8]uint32)
+		for forma, data := range c.announceData[medi].formats {
+			localSSRCs[forma] = data.localSSRC
+		}
+	} else {
+		localSSRCs, err = generateLocalSSRCs(
+			clientExtractExistingSSRCs(c.setuppedMedias),
+			medi.Formats,
+		)
+		if err != nil {
+			return nil, err
+		}
 	}
 
+	var udpRTPListener *clientUDPListener
+	var udpRTCPListener *clientUDPListener
+	var tcpChannel int
+	var srtpInCtx *wrappedSRTPContext
+	var srtpOutCtx *wrappedSRTPContext
+
+	defer func() {
+		if udpRTPListener != nil {
+			udpRTPListener.close()
+		}
+		if udpRTCPListener != nil {
+			udpRTCPListener.close()
+		}
+	}()
+
 	switch transport {
 	case TransportUDP, TransportUDPMulticast:
 		if c.Scheme == "rtsps" && !isSecure(th.Profile) {
-			cm.close()
 			return nil, fmt.Errorf("unable to setup secure UDP")
 		}
 
@@ -1640,29 +1702,27 @@ func (c *Client) doSetup(
 		if transport == TransportUDP {
 			if (rtpPort == 0 && rtcpPort != 0) ||
 				(rtpPort != 0 && rtcpPort == 0) {
-				cm.close()
 				return nil, liberrors.ErrClientUDPPortsZero{}
 			}
 
 			if rtpPort != 0 && rtcpPort != (rtpPort+1) {
-				cm.close()
 				return nil, liberrors.ErrClientUDPPortsNotConsecutive{}
 			}
 
-			err = cm.createUDPListeners(
+			udpRTPListener, udpRTCPListener, err = createUDPListenerPair(
+				c,
 				false,
 				nil,
 				net.JoinHostPort("", strconv.FormatInt(int64(rtpPort), 10)),
 				net.JoinHostPort("", strconv.FormatInt(int64(rtcpPort), 10)),
 			)
 			if err != nil {
-				cm.close()
 				return nil, err
 			}
 
 			v1 := headers.TransportDeliveryUnicast
 			th.Delivery = &v1
-			th.ClientPorts = &[2]int{cm.udpRTPListener.port(), cm.udpRTCPListener.port()}
+			th.ClientPorts = &[2]int{udpRTPListener.port(), udpRTCPListener.port()}
 		} else {
 			v1 := headers.TransportDeliveryMulticast
 			th.Delivery = &v1
@@ -1678,7 +1738,6 @@ func (c *Client) doSetup(
 
 	mediaURL, err := medi.URL(baseURL)
 	if err != nil {
-		cm.close()
 		return nil, err
 	}
 
@@ -1688,7 +1747,6 @@ func (c *Client) doSetup(
 
 	if medi.IsBackChannel {
 		if !c.RequestBackChannels {
-			cm.close()
 			return nil, fmt.Errorf("we are setupping a back channel but we did not request back channels")
 		}
 
@@ -1696,17 +1754,30 @@ func (c *Client) doSetup(
 	}
 
 	if isSecure(th.Profile) {
-		ssrcs := make([]uint32, len(cm.formats))
-		n := 0
-		for _, cf := range cm.formats {
-			ssrcs[n] = cf.localSSRC
-			n++
+		var srtpOutKey []byte
+
+		if c.state == clientStatePreRecord {
+			srtpOutKey = c.announceData[medi].srtpOutKey
+		} else {
+			srtpOutKey = make([]byte, srtpKeyLength)
+			_, err = rand.Read(srtpOutKey)
+			if err != nil {
+				return nil, err
+			}
+		}
+
+		srtpOutCtx = &wrappedSRTPContext{
+			key:   srtpOutKey,
+			ssrcs: ssrcsMapToList(localSSRCs),
+		}
+		err = srtpOutCtx.initialize()
+		if err != nil {
+			return nil, err
 		}
 
 		var mikeyMsg *mikey.Message
-		mikeyMsg, err = mikeyGenerate(cm.srtpOutCtx)
+		mikeyMsg, err = mikeyGenerate(srtpOutCtx)
 		if err != nil {
-			cm.close()
 			return nil, err
 		}
 
@@ -1716,7 +1787,6 @@ func (c *Client) doSetup(
 			MikeyMessage: mikeyMsg,
 		}.Marshal()
 		if err != nil {
-			cm.close()
 			return nil, err
 		}
 
@@ -1729,13 +1799,10 @@ func (c *Client) doSetup(
 		Header: header,
 	}, false)
 	if err != nil {
-		cm.close()
 		return nil, err
 	}
 
 	if res.StatusCode != base.StatusOK {
-		cm.close()
-
 		// switch transport automatically
 		if res.StatusCode == base.StatusUnsupportedTransport &&
 			c.setuppedTransport == nil && c.Transport == nil {
@@ -1753,15 +1820,12 @@ func (c *Client) doSetup(
 	var thRes headers.Transport
 	err = thRes.Unmarshal(res.Header["Transport"])
 	if err != nil {
-		cm.close()
 		return nil, liberrors.ErrClientTransportHeaderInvalid{Err: err}
 	}
 
 	switch transport {
 	case TransportUDP, TransportUDPMulticast:
 		if thRes.Protocol == headers.TransportProtocolTCP {
-			cm.close()
-
 			// switch transport automatically
 			if c.setuppedTransport == nil && c.Transport == nil {
 				c.OnTransportSwitch(liberrors.ErrClientSwitchToTCP2{})
@@ -1790,14 +1854,12 @@ func (c *Client) doSetup(
 	switch transport {
 	case TransportUDP:
 		if thRes.Delivery != nil && *thRes.Delivery != headers.TransportDeliveryUnicast {
-			cm.close()
 			return nil, liberrors.ErrClientTransportHeaderInvalidDelivery{}
 		}
 
 		serverPortsValid := thRes.ServerPorts != nil && !isAnyPort(thRes.ServerPorts[0]) && !isAnyPort(thRes.ServerPorts[1])
 
 		if (c.state == clientStatePreRecord || !c.AnyPortEnable) && !serverPortsValid {
-			cm.close()
 			return nil, liberrors.ErrClientServerPortsNotProvided{}
 		}
 
@@ -1810,41 +1872,38 @@ func (c *Client) doSetup(
 
 		if serverPortsValid {
 			if !c.AnyPortEnable {
-				cm.udpRTPListener.readPort = thRes.ServerPorts[0]
+				udpRTPListener.readPort = thRes.ServerPorts[0]
 			}
-			cm.udpRTPListener.writeAddr = &net.UDPAddr{
+			udpRTPListener.writeAddr = &net.UDPAddr{
 				IP:   remoteIP,
 				Zone: c.nconn.RemoteAddr().(*net.TCPAddr).Zone,
 				Port: thRes.ServerPorts[0],
 			}
 		}
-		cm.udpRTPListener.readIP = remoteIP
+		udpRTPListener.readIP = remoteIP
 
 		if serverPortsValid {
 			if !c.AnyPortEnable {
-				cm.udpRTCPListener.readPort = thRes.ServerPorts[1]
+				udpRTCPListener.readPort = thRes.ServerPorts[1]
 			}
-			cm.udpRTCPListener.writeAddr = &net.UDPAddr{
+			udpRTCPListener.writeAddr = &net.UDPAddr{
 				IP:   remoteIP,
 				Zone: c.nconn.RemoteAddr().(*net.TCPAddr).Zone,
 				Port: thRes.ServerPorts[1],
 			}
 		}
-		cm.udpRTCPListener.readIP = remoteIP
+		udpRTCPListener.readIP = remoteIP
 
 	case TransportUDPMulticast:
 		if thRes.Delivery == nil || *thRes.Delivery != headers.TransportDeliveryMulticast {
-			cm.close()
 			return nil, liberrors.ErrClientTransportHeaderInvalidDelivery{}
 		}
 
 		if thRes.Ports == nil {
-			cm.close()
 			return nil, liberrors.ErrClientTransportHeaderNoPorts{}
 		}
 
 		if thRes.Destination == nil {
-			cm.close()
 			return nil, liberrors.ErrClientTransportHeaderNoDestination{}
 		}
 
@@ -1858,72 +1917,65 @@ func (c *Client) doSetup(
 		var intf *net.Interface
 		intf, err = interfaceOfConn(c.nconn)
 		if err != nil {
-			cm.close()
 			return nil, err
 		}
 
-		err = cm.createUDPListeners(
+		udpRTPListener, udpRTCPListener, err = createUDPListenerPair(
+			c,
 			true,
 			intf,
 			net.JoinHostPort(thRes.Destination.String(), strconv.FormatInt(int64(thRes.Ports[0]), 10)),
 			net.JoinHostPort(thRes.Destination.String(), strconv.FormatInt(int64(thRes.Ports[1]), 10)),
 		)
 		if err != nil {
-			cm.close()
 			return nil, err
 		}
 
-		cm.udpRTPListener.readIP = remoteIP
-		cm.udpRTPListener.readPort = thRes.Ports[0]
-		cm.udpRTPListener.writeAddr = &net.UDPAddr{
+		udpRTPListener.readIP = remoteIP
+		udpRTPListener.readPort = thRes.Ports[0]
+		udpRTPListener.writeAddr = &net.UDPAddr{
 			IP:   remoteIP,
 			Port: thRes.Ports[0],
 		}
 
-		cm.udpRTCPListener.readIP = remoteIP
-		cm.udpRTCPListener.readPort = thRes.Ports[1]
-		cm.udpRTCPListener.writeAddr = &net.UDPAddr{
+		udpRTCPListener.readIP = remoteIP
+		udpRTCPListener.readPort = thRes.Ports[1]
+		udpRTCPListener.writeAddr = &net.UDPAddr{
 			IP:   remoteIP,
 			Port: thRes.Ports[1],
 		}
 
 	case TransportTCP:
 		if thRes.Protocol != headers.TransportProtocolTCP {
-			cm.close()
 			return nil, liberrors.ErrClientServerRequestedUDP{}
 		}
 
 		if thRes.Delivery != nil && *thRes.Delivery != headers.TransportDeliveryUnicast {
-			cm.close()
 			return nil, liberrors.ErrClientTransportHeaderInvalidDelivery{}
 		}
 
 		if thRes.InterleavedIDs == nil {
-			cm.close()
 			return nil, liberrors.ErrClientTransportHeaderNoInterleavedIDs{}
 		}
 
 		if (thRes.InterleavedIDs[0] + 1) != thRes.InterleavedIDs[1] {
-			cm.close()
 			return nil, liberrors.ErrClientTransportHeaderInvalidInterleavedIDs{}
 		}
 
 		if c.isChannelPairInUse(thRes.InterleavedIDs[0]) {
-			cm.close()
 			return &base.Response{
 				StatusCode: base.StatusBadRequest,
 			}, liberrors.ErrClientTransportHeaderInterleavedIDsInUse{}
 		}
 
-		cm.tcpChannel = thRes.InterleavedIDs[0]
+		tcpChannel = thRes.InterleavedIDs[0]
 	}
 
 	if thRes.Profile != th.Profile {
-		cm.close()
 		return nil, fmt.Errorf("returned profile does not match requested profile")
 	}
 
-	if cm.secure {
+	if isSecure(th.Profile) {
 		var mikeyMsg *mikey.Message
 
 		// extract key-mgmt from (in order of priority):
@@ -1935,7 +1987,6 @@ func (c *Client) doSetup(
 			var keyMgmt headers.KeyMgmt
 			err = keyMgmt.Unmarshal(res.Header["KeyMgmt"])
 			if err != nil {
-				cm.close()
 				return nil, err
 			}
 			mikeyMsg = keyMgmt.MikeyMessage
@@ -1950,13 +2001,28 @@ func (c *Client) doSetup(
 			return nil, fmt.Errorf("server did not provide key-mgmt data in any supported way")
 		}
 
-		cm.srtpInCtx, err = mikeyToContext(mikeyMsg)
+		srtpInCtx, err = mikeyToContext(mikeyMsg)
 		if err != nil {
-			cm.close()
 			return nil, err
 		}
 	}
 
+	cm := &clientMedia{
+		c:               c,
+		media:           medi,
+		secure:          isSecure(th.Profile),
+		udpRTPListener:  udpRTPListener,
+		udpRTCPListener: udpRTCPListener,
+		tcpChannel:      tcpChannel,
+		localSSRCs:      localSSRCs,
+		srtpInCtx:       srtpInCtx,
+		srtpOutCtx:      srtpOutCtx,
+	}
+	cm.initialize()
+
+	udpRTPListener = nil
+	udpRTCPListener = nil
+
 	if c.setuppedMedias == nil {
 		c.setuppedMedias = make(map[*description.Media]*clientMedia)
 	}
@@ -2309,13 +2375,6 @@ func (c *Client) WritePacketRTPWithNTP(medi *description.Media, pkt *rtp.Packet,
 	default:
 	}
 
-	c.writerMutex.RLock()
-	defer c.writerMutex.RUnlock()
-
-	if c.writer == nil {
-		return nil
-	}
-
 	cm := c.setuppedMedias[medi]
 	cf := cm.formats[pkt.PayloadType]
 	return cf.writePacketRTP(pkt, ntp)
@@ -2329,13 +2388,6 @@ func (c *Client) WritePacketRTCP(medi *description.Media, pkt rtcp.Packet) error
 	default:
 	}
 
-	c.writerMutex.RLock()
-	defer c.writerMutex.RUnlock()
-
-	if c.writer == nil {
-		return nil
-	}
-
 	cm := c.setuppedMedias[medi]
 	return cm.writePacketRTCP(pkt)
 }
diff --git a/client_format.go b/client_format.go
index befd91a3..068f298f 100644
--- a/client_format.go
+++ b/client_format.go
@@ -1,7 +1,6 @@
 package gortsplib
 
 import (
-	"slices"
 	"sync/atomic"
 	"time"
 
@@ -14,37 +13,12 @@ import (
 	"github.com/bluenviron/gortsplib/v4/pkg/rtpsender"
 )
 
-func clientPickLocalSSRC(cf *clientFormat) (uint32, error) {
-	var takenSSRCs []uint32 //nolint:prealloc
-
-	for _, cm := range cf.cm.c.setuppedMedias {
-		for _, cf := range cm.formats {
-			takenSSRCs = append(takenSSRCs, cf.localSSRC)
-		}
-	}
-
-	for _, cf := range cf.cm.formats {
-		takenSSRCs = append(takenSSRCs, cf.localSSRC)
-	}
-
-	for {
-		ssrc, err := randUint32()
-		if err != nil {
-			return 0, err
-		}
-
-		if ssrc != 0 && !slices.Contains(takenSSRCs, ssrc) {
-			return ssrc, nil
-		}
-	}
-}
-
 type clientFormat struct {
 	cm          *clientMedia
 	format      format.Format
+	localSSRC   uint32
 	onPacketRTP OnPacketRTPFunc
 
-	localSSRC             uint32
 	rtpReceiver           *rtpreceiver.Receiver // play
 	rtpSender             *rtpsender.Sender     // record or back channel
 	writePacketRTPInQueue func([]byte) error
@@ -53,32 +27,18 @@ type clientFormat struct {
 	rtpPacketsLost        *uint64
 }
 
-func (cf *clientFormat) initialize() error {
-	if cf.cm.c.state == clientStatePreRecord {
-		cf.localSSRC = cf.cm.c.announceData[cf.cm.media].formats[cf.format.PayloadType()].localSSRC
-	} else {
-		var err error
-		cf.localSSRC, err = clientPickLocalSSRC(cf)
-		if err != nil {
-			return err
-		}
-	}
-
+func (cf *clientFormat) initialize() {
 	cf.rtpPacketsReceived = new(uint64)
 	cf.rtpPacketsSent = new(uint64)
 	cf.rtpPacketsLost = new(uint64)
 
-	return nil
-}
-
-func (cf *clientFormat) start() {
 	if cf.cm.udpRTPListener != nil {
 		cf.writePacketRTPInQueue = cf.writePacketRTPInQueueUDP
 	} else {
 		cf.writePacketRTPInQueue = cf.writePacketRTPInQueueTCP
 	}
 
-	if cf.cm.c.state == clientStateRecord || cf.cm.media.IsBackChannel {
+	if cf.cm.c.state == clientStatePreRecord || cf.cm.media.IsBackChannel {
 		cf.rtpSender = &rtpsender.Sender{
 			ClockRate: cf.format.ClockRate(),
 			Period:    cf.cm.c.senderReportPeriod,
@@ -110,7 +70,7 @@ func (cf *clientFormat) start() {
 	}
 }
 
-func (cf *clientFormat) stop() {
+func (cf *clientFormat) close() {
 	if cf.rtpReceiver != nil {
 		cf.rtpReceiver.Close()
 		cf.rtpReceiver = nil
@@ -178,6 +138,13 @@ func (cf *clientFormat) writePacketRTP(pkt *rtp.Packet, ntp time.Time) error {
 		buf = encr
 	}
 
+	cf.cm.c.writerMutex.RLock()
+	defer cf.cm.c.writerMutex.RUnlock()
+
+	if cf.cm.c.writer == nil {
+		return nil
+	}
+
 	ok := cf.cm.c.writer.push(func() error {
 		return cf.writePacketRTPInQueue(buf)
 	})
diff --git a/client_media.go b/client_media.go
index 033146d1..c39a162d 100644
--- a/client_media.go
+++ b/client_media.go
@@ -1,7 +1,6 @@
 package gortsplib
 
 import (
-	"crypto/rand"
 	"fmt"
 	"net"
 	"strconv"
@@ -15,18 +14,87 @@ import (
 	"github.com/bluenviron/gortsplib/v4/pkg/liberrors"
 )
 
-type clientMedia struct {
-	c      *Client
-	media  *description.Media
-	secure bool
+func createUDPListenerPair(
+	c *Client,
+	multicast bool,
+	multicastInterface *net.Interface,
+	rtpAddress string,
+	rtcpAddress string,
+) (*clientUDPListener, *clientUDPListener, error) {
+	if rtpAddress != ":0" {
+		l1 := &clientUDPListener{
+			c:                  c,
+			multicast:          multicast,
+			multicastInterface: multicastInterface,
+			address:            rtpAddress,
+		}
+		err := l1.initialize()
+		if err != nil {
+			return nil, nil, err
+		}
+
+		l2 := &clientUDPListener{
+			c:                  c,
+			multicast:          multicast,
+			multicastInterface: multicastInterface,
+			address:            rtcpAddress,
+		}
+		err = l2.initialize()
+		if err != nil {
+			l1.close()
+			return nil, nil, err
+		}
+
+		return l1, l2, nil
+	}
+
+	// pick two consecutive ports in range 65535-10000
+	// RTP port must be even and RTCP port odd
+	for {
+		v, err := randInRange((65535 - 10000) / 2)
+		if err != nil {
+			return nil, nil, err
+		}
+
+		rtpPort := v*2 + 10000
+		rtcpPort := rtpPort + 1
+
+		l1 := &clientUDPListener{
+			c:       c,
+			address: net.JoinHostPort("", strconv.FormatInt(int64(rtpPort), 10)),
+		}
+		err = l1.initialize()
+		if err != nil {
+			continue
+		}
+
+		l2 := &clientUDPListener{
+			c:       c,
+			address: net.JoinHostPort("", strconv.FormatInt(int64(rtcpPort), 10)),
+		}
+		err = l2.initialize()
+		if err != nil {
+			l2.close()
+			continue
+		}
+
+		return l1, l2, nil
+	}
+}
+
+type clientMedia struct {
+	c               *Client
+	media           *description.Media
+	secure          bool
+	udpRTPListener  *clientUDPListener
+	udpRTCPListener *clientUDPListener
+	tcpChannel      int
+	localSSRCs      map[uint8]uint32
+	srtpInCtx       *wrappedSRTPContext
+	srtpOutCtx      *wrappedSRTPContext
 
-	srtpOutCtx             *wrappedSRTPContext
-	srtpInCtx              *wrappedSRTPContext
 	onPacketRTCP           OnPacketRTCPFunc
 	formats                map[uint8]*clientFormat
-	tcpChannel             int
-	udpRTPListener         *clientUDPListener
-	udpRTCPListener        *clientUDPListener
 	writePacketRTCPInQueue func([]byte) error
 	bytesReceived          *uint64
 	bytesSent              *uint64
@@ -36,7 +104,7 @@ type clientMedia struct {
 	rtcpPacketsInError     *uint64
 }
 
-func (cm *clientMedia) initialize() error {
+func (cm *clientMedia) initialize() {
 	cm.onPacketRTCP = func(rtcp.Packet) {}
 	cm.bytesReceived = new(uint64)
 	cm.bytesSent = new(uint64)
@@ -51,123 +119,19 @@ func (cm *clientMedia) initialize() error {
 		f := &clientFormat{
 			cm:          cm,
 			format:      forma,
+			localSSRC:   cm.localSSRCs[forma.PayloadType()],
 			onPacketRTP: func(*rtp.Packet) {},
 		}
-		err := f.initialize()
-		if err != nil {
-			return err
-		}
-
+		f.initialize()
 		cm.formats[forma.PayloadType()] = f
 	}
-
-	if cm.secure {
-		var srtpOutKey []byte
-		if cm.c.state == clientStatePreRecord {
-			srtpOutKey = cm.c.announceData[cm.media].srtpOutKey
-		} else {
-			srtpOutKey = make([]byte, srtpKeyLength)
-			_, err := rand.Read(srtpOutKey)
-			if err != nil {
-				return err
-			}
-		}
-
-		ssrcs := make([]uint32, len(cm.formats))
-		n := 0
-		for _, cf := range cm.formats {
-			ssrcs[n] = cf.localSSRC
-			n++
-		}
-
-		cm.srtpOutCtx = &wrappedSRTPContext{
-			key:   srtpOutKey,
-			ssrcs: ssrcs,
-		}
-		err := cm.srtpOutCtx.initialize()
-		if err != nil {
-			return err
-		}
-	}
-
-	return nil
 }
 
 func (cm *clientMedia) close() {
-	if cm.udpRTPListener != nil {
-		cm.udpRTPListener.close()
-		cm.udpRTCPListener.close()
-	}
-}
+	cm.stop()
 
-func (cm *clientMedia) createUDPListeners(
-	multicast bool,
-	multicastInterface *net.Interface,
-	rtpAddress string,
-	rtcpAddress string,
-) error {
-	if rtpAddress != ":0" {
-		l1 := &clientUDPListener{
-			c:                  cm.c,
-			multicast:          multicast,
-			multicastInterface: multicastInterface,
-			address:            rtpAddress,
-		}
-		err := l1.initialize()
-		if err != nil {
-			return err
-		}
-
-		l2 := &clientUDPListener{
-			c:                  cm.c,
-			multicast:          multicast,
-			multicastInterface: multicastInterface,
-			address:            rtcpAddress,
-		}
-		err = l2.initialize()
-		if err != nil {
-			l1.close()
-			return err
-		}
-
-		cm.udpRTPListener, cm.udpRTCPListener = l1, l2
-		return nil
-	}
-
-	// pick two consecutive ports in range 65535-10000
-	// RTP port must be even and RTCP port odd
-	for {
-		v, err := randInRange((65535 - 10000) / 2)
-		if err != nil {
-			return err
-		}
-
-		rtpPort := v*2 + 10000
-		rtcpPort := rtpPort + 1
-
-		cm.udpRTPListener = &clientUDPListener{
-			c:       cm.c,
-			address: net.JoinHostPort("", strconv.FormatInt(int64(rtpPort), 10)),
-		}
-		err = cm.udpRTPListener.initialize()
-		if err != nil {
-			cm.udpRTPListener = nil
-			continue
-		}
-
-		cm.udpRTCPListener = &clientUDPListener{
-			c:       cm.c,
-			address: net.JoinHostPort("", strconv.FormatInt(int64(rtcpPort), 10)),
-		}
-		err = cm.udpRTCPListener.initialize()
-		if err != nil {
-			cm.udpRTPListener.close()
-			cm.udpRTPListener = nil
-			cm.udpRTCPListener = nil
-			continue
-		}
-
-		return nil
+	for _, ct := range cm.formats {
+		ct.close()
 	}
 }
 
@@ -198,10 +162,6 @@ func (cm *clientMedia) start() {
 		}
 	}
 
-	for _, ct := range cm.formats {
-		ct.start()
-	}
-
 	if cm.udpRTPListener != nil {
 		cm.udpRTPListener.start()
 		cm.udpRTCPListener.start()
@@ -213,10 +173,6 @@ func (cm *clientMedia) stop() {
 		cm.udpRTPListener.stop()
 		cm.udpRTCPListener.stop()
 	}
-
-	for _, ct := range cm.formats {
-		ct.stop()
-	}
 }
 
 func (cm *clientMedia) findFormatByRemoteSSRC(ssrc uint32) *clientFormat {
@@ -460,6 +416,13 @@ func (cm *clientMedia) writePacketRTCP(pkt rtcp.Packet) error {
 		buf = encr
 	}
 
+	cm.c.writerMutex.RLock()
+	defer cm.c.writerMutex.RUnlock()
+
+	if cm.c.writer == nil {
+		return nil
+	}
+
 	ok := cm.c.writer.push(func() error {
 		return cm.writePacketRTCPInQueue(buf)
 	})
diff --git a/server_session.go b/server_session.go
index dc3c2f30..68b48e46 100644
--- a/server_session.go
+++ b/server_session.go
@@ -3,6 +3,7 @@ package gortsplib
 import (
 	"bytes"
 	"context"
+	"crypto/rand"
 	"fmt"
 	"log"
 	"net"
@@ -31,6 +32,16 @@ import (
 
 type readFunc func([]byte) bool
 
+func serverSessionExtractExistingSSRCs(medias map[*description.Media]*serverSessionMedia) []uint32 {
+	var ret []uint32
+	for _, media := range medias {
+		for _, forma := range media.formats {
+			ret = append(ret, forma.localSSRC)
+		}
+	}
+	return ret
+}
+
 func isSecure(profile headers.TransportProfile) bool {
 	return profile == headers.TransportProfileSAVP
 }
@@ -433,8 +444,8 @@ type ServerSession struct {
 	announcedDesc         *description.Session // record
 	udpLastPacketTime     *int64               // record
 	udpCheckStreamTimer   *time.Timer
-	writer                *asyncProcessor
 	writerMutex           sync.RWMutex
+	writer                *asyncProcessor
 	timeDecoder           *rtptime.GlobalDecoder2
 	tcpFrame              *base.InterleavedFrame
 	tcpBuffer             []byte
@@ -818,7 +829,7 @@ func (ss *ServerSession) run() {
 	}
 
 	for _, sm := range ss.setuppedMedias {
-		sm.stop()
+		sm.close()
 	}
 
 	if ss.writer != nil {
@@ -1290,37 +1301,76 @@ func (ss *ServerSession) handleRequestInner(sc *ServerConn, req *base.Request) (
 				res.Header = make(base.Header)
 			}
 
-			sm := &serverSessionMedia{
-				ss:           ss,
-				media:        medi,
-				srtpInCtx:    srtpInCtx,
-				onPacketRTCP: func(_ rtcp.Packet) {},
+			var localSSRCs map[uint8]uint32
+
+			if ss.state == ServerSessionStatePreRecord || medi.IsBackChannel {
+				localSSRCs, err = generateLocalSSRCs(
+					serverSessionExtractExistingSSRCs(ss.setuppedMedias),
+					medi.Formats,
+				)
+				if err != nil {
+					return &base.Response{
+						StatusCode: base.StatusInternalServerError,
+					}, err
+				}
+			} else {
+				localSSRCs = make(map[uint8]uint32)
+				for forma, data := range ss.setuppedStream.medias[medi].formats {
+					localSSRCs[forma] = data.localSSRC
+				}
 			}
-			err = sm.initialize()
-			if err != nil {
-				return &base.Response{
-					StatusCode: base.StatusInternalServerError,
-				}, err
+
+			var srtpOutCtx *wrappedSRTPContext
+
+			if ss.s.TLSConfig != nil {
+				if ss.state == ServerSessionStatePreRecord || medi.IsBackChannel {
+					srtpOutKey := make([]byte, srtpKeyLength)
+					_, err = rand.Read(srtpOutKey)
+					if err != nil {
+						return &base.Response{
+							StatusCode: base.StatusInternalServerError,
+						}, err
+					}
+
+					srtpOutCtx = &wrappedSRTPContext{
+						key:   srtpOutKey,
+						ssrcs: ssrcsMapToList(localSSRCs),
+					}
+					err = srtpOutCtx.initialize()
+					if err != nil {
+						return &base.Response{
+							StatusCode: base.StatusInternalServerError,
+						}, err
+					}
+				} else {
+					srtpOutCtx = ss.setuppedStream.medias[medi].srtpOutCtx
+				}
 			}
 
+			var udpRTPReadPort int
+			var udpRTPWriteAddr *net.UDPAddr
+			var udpRTCPReadPort int
+			var udpRTCPWriteAddr *net.UDPAddr
+			var tcpChannel int
+
 			switch transport {
 			case TransportUDP, TransportUDPMulticast:
 				th.Protocol = headers.TransportProtocolUDP
 
 				if transport == TransportUDP {
-					sm.udpRTPReadPort = inTH.ClientPorts[0]
-					sm.udpRTCPReadPort = inTH.ClientPorts[1]
+					udpRTPReadPort = inTH.ClientPorts[0]
+					udpRTCPReadPort = inTH.ClientPorts[1]
 
-					sm.udpRTPWriteAddr = &net.UDPAddr{
+					udpRTPWriteAddr = &net.UDPAddr{
 						IP:   ss.author.ip(),
 						Zone: ss.author.zone(),
-						Port: sm.udpRTPReadPort,
+						Port: udpRTPReadPort,
 					}
 
-					sm.udpRTCPWriteAddr = &net.UDPAddr{
+					udpRTCPWriteAddr = &net.UDPAddr{
 						IP:   ss.author.ip(),
 						Zone: ss.author.zone(),
-						Port: sm.udpRTCPReadPort,
+						Port: udpRTCPReadPort,
 					}
 
 					de := headers.TransportDeliveryUnicast
@@ -1341,32 +1391,41 @@ func (ss *ServerSession) handleRequestInner(sc *ServerConn, req *base.Request) (
 				th.Protocol = headers.TransportProtocolTCP
 
 				if inTH.InterleavedIDs != nil {
-					sm.tcpChannel = inTH.InterleavedIDs[0]
+					tcpChannel = inTH.InterleavedIDs[0]
 				} else {
-					sm.tcpChannel = ss.findFreeChannelPair()
+					tcpChannel = ss.findFreeChannelPair()
 				}
 
 				de := headers.TransportDeliveryUnicast
 				th.Delivery = &de
-				th.InterleavedIDs = &[2]int{sm.tcpChannel, sm.tcpChannel + 1}
+				th.InterleavedIDs = &[2]int{tcpChannel, tcpChannel + 1}
 			}
 
+			sm := &serverSessionMedia{
+				ss:               ss,
+				media:            medi,
+				localSSRCs:       localSSRCs,
+				srtpInCtx:        srtpInCtx,
+				srtpOutCtx:       srtpOutCtx,
+				udpRTPReadPort:   udpRTPReadPort,
+				udpRTPWriteAddr:  udpRTPWriteAddr,
+				udpRTCPReadPort:  udpRTCPReadPort,
+				udpRTCPWriteAddr: udpRTCPWriteAddr,
+				tcpChannel:       tcpChannel,
+				onPacketRTCP:     func(_ rtcp.Packet) {},
+			}
+			sm.initialize()
+
 			if ss.setuppedMedias == nil {
 				ss.setuppedMedias = make(map[*description.Media]*serverSessionMedia)
 			}
+
 			ss.setuppedMedias[medi] = sm
 			ss.setuppedMediasOrdered = append(ss.setuppedMediasOrdered, sm)
 
 			res.Header["Transport"] = th.Marshal()
 
 			if isSecure(inTH.Profile) {
-				ssrcs := make([]uint32, len(sm.formats))
-				n := 0
-				for _, sf := range sm.formats {
-					ssrcs[n] = sf.localSSRC
-					n++
-				}
-
 				var mk *mikey.Message
 				mk, err = mikeyGenerate(sm.srtpOutCtx)
 				if err != nil {
diff --git a/server_session_format.go b/server_session_format.go
index dcaf8b18..e581bba3 100644
--- a/server_session_format.go
+++ b/server_session_format.go
@@ -2,7 +2,6 @@ package gortsplib
 
 import (
 	"log"
-	"slices"
 	"sync/atomic"
 	"time"
 
@@ -14,37 +13,12 @@ import (
 	"github.com/bluenviron/gortsplib/v4/pkg/rtpreceiver"
 )
 
-func serverSessionPickLocalSSRC(sf *serverSessionFormat) (uint32, error) {
-	var takenSSRCs []uint32 //nolint:prealloc
-
-	for _, sm := range sf.sm.ss.setuppedMedias {
-		for _, sf := range sm.formats {
-			takenSSRCs = append(takenSSRCs, sf.localSSRC)
-		}
-	}
-
-	for _, sf := range sf.sm.formats {
-		takenSSRCs = append(takenSSRCs, sf.localSSRC)
-	}
-
-	for {
-		ssrc, err := randUint32()
-		if err != nil {
-			return 0, err
-		}
-
-		if ssrc != 0 && !slices.Contains(takenSSRCs, ssrc) {
-			return ssrc, nil
-		}
-	}
-}
-
 type serverSessionFormat struct {
 	sm          *serverSessionMedia
 	format      format.Format
+	localSSRC   uint32
 	onPacketRTP OnPacketRTPFunc
 
-	localSSRC             uint32
 	rtpReceiver           *rtpreceiver.Receiver
 	writePacketRTPInQueue func([]byte) error
 	rtpPacketsReceived    *uint64
@@ -52,25 +26,11 @@ type serverSessionFormat struct {
 	rtpPacketsLost        *uint64
 }
 
-func (sf *serverSessionFormat) initialize() error {
-	if sf.sm.ss.state == ServerSessionStatePreRecord || sf.sm.media.IsBackChannel {
-		var err error
-		sf.localSSRC, err = serverSessionPickLocalSSRC(sf)
-		if err != nil {
-			return err
-		}
-	} else {
-		sf.localSSRC = sf.sm.ss.setuppedStream.medias[sf.sm.media].formats[sf.format.PayloadType()].localSSRC
-	}
-
+func (sf *serverSessionFormat) initialize() {
 	sf.rtpPacketsReceived = new(uint64)
 	sf.rtpPacketsSent = new(uint64)
 	sf.rtpPacketsLost = new(uint64)
 
-	return nil
-}
-
-func (sf *serverSessionFormat) start() {
 	udp := *sf.sm.ss.setuppedTransport == TransportUDP || *sf.sm.ss.setuppedTransport == TransportUDPMulticast
 
 	if udp {
@@ -79,7 +39,7 @@ func (sf *serverSessionFormat) start() {
 		sf.writePacketRTPInQueue = sf.writePacketRTPInQueueTCP
 	}
 
-	if sf.sm.ss.state == ServerSessionStateRecord || sf.sm.media.IsBackChannel {
+	if sf.sm.ss.state == ServerSessionStatePreRecord || sf.sm.media.IsBackChannel {
 		sf.rtpReceiver = &rtpreceiver.Receiver{
 			ClockRate:            sf.format.ClockRate(),
 			LocalSSRC:            &sf.localSSRC,
@@ -99,7 +59,7 @@ func (sf *serverSessionFormat) start() {
 	}
 }
 
-func (sf *serverSessionFormat) stop() {
+func (sf *serverSessionFormat) close() {
 	if sf.rtpReceiver != nil {
 		sf.rtpReceiver.Close()
 		sf.rtpReceiver = nil
diff --git a/server_session_media.go b/server_session_media.go
index 7b78f814..fe0c2355 100644
--- a/server_session_media.go
+++ b/server_session_media.go
@@ -1,7 +1,6 @@
 package gortsplib
 
 import (
-	"crypto/rand"
 	"fmt"
 	"log"
 	"net"
@@ -16,17 +15,18 @@ import (
 )
 
 type serverSessionMedia struct {
-	ss           *ServerSession
-	media        *description.Media
-	srtpInCtx    *wrappedSRTPContext
-	onPacketRTCP OnPacketRTCPFunc
+	ss               *ServerSession
+	media            *description.Media
+	localSSRCs       map[uint8]uint32
+	srtpInCtx        *wrappedSRTPContext
+	srtpOutCtx       *wrappedSRTPContext
+	udpRTPReadPort   int
+	udpRTPWriteAddr  *net.UDPAddr
+	udpRTCPReadPort  int
+	udpRTCPWriteAddr *net.UDPAddr
+	tcpChannel       int
+	onPacketRTCP     OnPacketRTCPFunc
 
-	srtpOutCtx             *wrappedSRTPContext
-	tcpChannel             int
-	udpRTPReadPort         int
-	udpRTPWriteAddr        *net.UDPAddr
-	udpRTCPReadPort        int
-	udpRTCPWriteAddr       *net.UDPAddr
 	formats                map[uint8]*serverSessionFormat // record only
 	writePacketRTCPInQueue func([]byte) error
 	bytesReceived          *uint64
@@ -37,7 +37,7 @@ type serverSessionMedia struct {
 	rtcpPacketsInError     *uint64
 }
 
-func (sm *serverSessionMedia) initialize() error {
+func (sm *serverSessionMedia) initialize() {
 	sm.bytesReceived = new(uint64)
 	sm.bytesSent = new(uint64)
 	sm.rtpPacketsInError = new(uint64)
@@ -51,54 +51,23 @@ func (sm *serverSessionMedia) initialize() error {
 		f := &serverSessionFormat{
 			sm:          sm,
 			format:      forma,
+			localSSRC:   sm.localSSRCs[forma.PayloadType()],
 			onPacketRTP: func(*rtp.Packet) {},
 		}
-		err := f.initialize()
-		if err != nil {
-			return err
-		}
+		f.initialize()
 		sm.formats[forma.PayloadType()] = f
 	}
+}
 
-	if sm.ss.s.TLSConfig != nil {
-		if sm.ss.state == ServerSessionStatePreRecord || sm.media.IsBackChannel {
-			srtpOutKey := make([]byte, srtpKeyLength)
-			_, err := rand.Read(srtpOutKey)
-			if err != nil {
-				return err
-			}
+func (sm *serverSessionMedia) close() {
+	sm.stop()
 
-			ssrcs := make([]uint32, len(sm.formats))
-			n := 0
-			for _, cf := range sm.formats {
-				ssrcs[n] = cf.localSSRC
-				n++
-			}
-
-			sm.srtpOutCtx = &wrappedSRTPContext{
-				key:   srtpOutKey,
-				ssrcs: ssrcs,
-			}
-			err = sm.srtpOutCtx.initialize()
-			if err != nil {
-				return err
-			}
-		} else {
-			streamMedia := sm.ss.setuppedStream.medias[sm.media]
-			sm.srtpOutCtx = streamMedia.srtpOutCtx
-		}
+	for _, forma := range sm.formats {
+		forma.close()
 	}
-
-	return nil
 }
 
 func (sm *serverSessionMedia) start() error {
-	// allocate udpRTCPReceiver before udpRTCPListener
-	// otherwise udpRTCPReceiver.LastSSRC() cannot be called.
-	for _, sf := range sm.formats {
-		sf.start()
-	}
-
 	switch *sm.ss.setuppedTransport {
 	case TransportUDP, TransportUDPMulticast:
 		sm.writePacketRTCPInQueue = sm.writePacketRTCPInQueueUDP
@@ -168,10 +137,6 @@ func (sm *serverSessionMedia) stop() {
 		sm.ss.s.udpRTPListener.removeClient(sm.ss.author.ip(), sm.udpRTPReadPort)
 		sm.ss.s.udpRTCPListener.removeClient(sm.ss.author.ip(), sm.udpRTCPReadPort)
 	}
-
-	for _, sf := range sm.formats {
-		sf.stop()
-	}
 }
 
 func (sm *serverSessionMedia) findFormatByRemoteSSRC(ssrc uint32) *serverSessionFormat {
diff --git a/server_stream.go b/server_stream.go
index 3f3c7171..f1549044 100644
--- a/server_stream.go
+++ b/server_stream.go
@@ -1,6 +1,7 @@
 package gortsplib
 
 import (
+	"crypto/rand"
 	"fmt"
 	"sync"
 	"sync/atomic"
@@ -14,6 +15,16 @@ import (
 	"github.com/bluenviron/gortsplib/v4/pkg/liberrors"
 )
 
+func serverStreamExtractExistingSSRCs(medias map[*description.Media]*serverStreamMedia) []uint32 {
+	var ret []uint32
+	for _, media := range medias {
+		for _, forma := range media.formats {
+			ret = append(ret, forma.localSSRC)
+		}
+	}
+	return ret
+}
+
 // NewServerStream allocates a ServerStream.
 //
 // Deprecated: replaced by ServerStream.Initialize().
@@ -56,20 +67,53 @@ func (st *ServerStream) Initialize() error {
 	st.activeUnicastReaders = make(map[*ServerSession]struct{})
 
 	st.medias = make(map[*description.Media]*serverStreamMedia, len(st.Desc.Medias))
+
 	for i, medi := range st.Desc.Medias {
-		sm := &serverStreamMedia{
-			st:      st,
-			media:   medi,
-			trackID: i,
-		}
-		err := sm.initialize()
+		localSSRCs, err := generateLocalSSRCs(
+			serverStreamExtractExistingSSRCs(st.medias),
+			medi.Formats,
+		)
 		if err != nil {
-			for _, medi := range st.Desc.Medias[:i] {
-				st.medias[medi].close()
+			for _, sm := range st.medias {
+				sm.close()
 			}
 			return err
 		}
 
+		var srtpOutCtx *wrappedSRTPContext
+
+		if st.Server.TLSConfig != nil {
+			srtpOutKey := make([]byte, srtpKeyLength)
+			_, err = rand.Read(srtpOutKey)
+			if err != nil {
+				for _, sm := range st.medias {
+					sm.close()
+				}
+				return err
+			}
+
+			srtpOutCtx = &wrappedSRTPContext{
+				key:   srtpOutKey,
+				ssrcs: ssrcsMapToList(localSSRCs),
+			}
+			err = srtpOutCtx.initialize()
+			if err != nil {
+				for _, sm := range st.medias {
+					sm.close()
+				}
+				return err
+			}
+		}
+
+		sm := &serverStreamMedia{
+			st:         st,
+			media:      medi,
+			trackID:    i,
+			localSSRCs: localSSRCs,
+			srtpOutCtx: srtpOutCtx,
+		}
+		sm.initialize()
+
 		st.medias[medi] = sm
 	}
 
diff --git a/server_stream_format.go b/server_stream_format.go
index 194bc9b7..eb14cc62 100644
--- a/server_stream_format.go
+++ b/server_stream_format.go
@@ -2,7 +2,6 @@ package gortsplib
 
 import (
 	"crypto/rand"
-	"slices"
 	"sync/atomic"
 	"time"
 
@@ -22,47 +21,16 @@ func randUint32() (uint32, error) {
 	return uint32(b[0])<<24 | uint32(b[1])<<16 | uint32(b[2])<<8 | uint32(b[3]), nil
 }
 
-func serverStreamPickLocalSSRC(sf *serverStreamFormat) (uint32, error) {
-	var takenSSRCs []uint32 //nolint:prealloc
-
-	for _, sm := range sf.sm.st.medias {
-		for _, sf := range sm.formats {
-			takenSSRCs = append(takenSSRCs, sf.localSSRC)
-		}
-	}
-
-	for _, sf := range sf.sm.formats {
-		takenSSRCs = append(takenSSRCs, sf.localSSRC)
-	}
-
-	for {
-		ssrc, err := randUint32()
-		if err != nil {
-			return 0, err
-		}
-
-		if ssrc != 0 && !slices.Contains(takenSSRCs, ssrc) {
-			return ssrc, nil
-		}
-	}
-}
-
 type serverStreamFormat struct {
-	sm     *serverStreamMedia
-	format format.Format
+	sm        *serverStreamMedia
+	format    format.Format
+	localSSRC uint32
 
-	localSSRC      uint32
 	rtpSender      *rtpsender.Sender
 	rtpPacketsSent *uint64
 }
 
-func (sf *serverStreamFormat) initialize() error {
-	var err error
-	sf.localSSRC, err = serverStreamPickLocalSSRC(sf)
-	if err != nil {
-		return err
-	}
-
+func (sf *serverStreamFormat) initialize() {
 	sf.rtpPacketsSent = new(uint64)
 
 	sf.rtpSender = &rtpsender.Sender{
@@ -76,8 +44,6 @@ func (sf *serverStreamFormat) initialize() error {
 		},
 	}
 	sf.rtpSender.Initialize()
-
-	return nil
 }
 
 func (sf *serverStreamFormat) close() {
diff --git a/server_stream_media.go b/server_stream_media.go
index ae4bef16..80058985 100644
--- a/server_stream_media.go
+++ b/server_stream_media.go
@@ -1,7 +1,6 @@
 package gortsplib
 
 import (
-	"crypto/rand"
 	"fmt"
 	"sync/atomic"
 
@@ -10,64 +9,33 @@ import (
 )
 
 type serverStreamMedia struct {
-	st      *ServerStream
-	media   *description.Media
-	trackID int
+	st         *ServerStream
+	media      *description.Media
+	trackID    int
+	localSSRCs map[uint8]uint32
+	srtpOutCtx *wrappedSRTPContext
 
-	srtpOutCtx      *wrappedSRTPContext
 	formats         map[uint8]*serverStreamFormat
 	multicastWriter *serverMulticastWriter
 	bytesSent       *uint64
 	rtcpPacketsSent *uint64
 }
 
-func (sm *serverStreamMedia) initialize() error {
+func (sm *serverStreamMedia) initialize() {
 	sm.bytesSent = new(uint64)
 	sm.rtcpPacketsSent = new(uint64)
 
 	sm.formats = make(map[uint8]*serverStreamFormat)
 
-	for i, forma := range sm.media.Formats {
+	for _, forma := range sm.media.Formats {
 		sf := &serverStreamFormat{
-			sm:     sm,
-			format: forma,
+			sm:        sm,
+			format:    forma,
+			localSSRC: sm.localSSRCs[forma.PayloadType()],
 		}
-		err := sf.initialize()
-		if err != nil {
-			for _, forma := range sm.media.Formats[:i] {
-				sm.formats[forma.PayloadType()].close()
-			}
-			return err
-		}
-
+		sf.initialize()
 		sm.formats[forma.PayloadType()] = sf
 	}
-
-	if sm.st.Server.TLSConfig != nil {
-		srtpOutKey := make([]byte, srtpKeyLength)
-		_, err := rand.Read(srtpOutKey)
-		if err != nil {
-			return err
-		}
-
-		ssrcs := make([]uint32, len(sm.formats))
-		n := 0
-		for _, cf := range sm.formats {
-			ssrcs[n] = cf.localSSRC
-			n++
-		}
-
-		sm.srtpOutCtx = &wrappedSRTPContext{
-			key:   srtpOutKey,
-			ssrcs: ssrcs,
-		}
-		err = sm.srtpOutCtx.initialize()
-		if err != nil {
-			return err
-		}
-	}
-
-	return nil
 }
 
 func (sm *serverStreamMedia) close() {