diff --git a/Makefile b/Makefile
index e22b30ad..2e9a9ee8 100644
--- a/Makefile
+++ b/Makefile
@@ -75,9 +75,10 @@ paths:
 #    readPass: tast
 
   proxied:
-    source: rtsp://192.168.2.198:8554/stream
-    sourceProtocol: tcp
-    sourceOnDemand: yes
+#    source: rtsp://192.168.2.198:8554/stream
+#    sourceProtocol: tcp
+#    sourceOnDemand: yes
+    runOnDemand: ffmpeg -i rtsp://192.168.2.198:8554/stream -c copy -f rtsp rtsp://localhost:8554/proxied2
 
 #  original:
 #    runOnPublish: ffmpeg -i rtsp://localhost:8554/original -b:a 64k -c:v libx264 -preset ultrafast -b:v 500k -max_muxing_queue_size 1024 -f rtsp rtsp://localhost:8554/compressed
diff --git a/client.go b/client.go
index be50cbbc..f55f98d5 100644
--- a/client.go
+++ b/client.go
@@ -23,6 +23,11 @@ const (
 	clientUdpWriteBufferSize     = 128 * 1024
 )
 
+type describeRes struct {
+	sdp []byte
+	err error
+}
+
 type clientTrack struct {
 	rtpPort  int
 	rtcpPort int
@@ -77,7 +82,7 @@ type client struct {
 	p              *program
 	conn           *gortsplib.ConnServer
 	state          clientState
-	path           string
+	pathId         string
 	authUser       string
 	authPass       string
 	authHelper     *gortsplib.AuthServer
@@ -88,12 +93,12 @@ type client struct {
 	readBuf        *doubleBuffer
 	writeBuf       *doubleBuffer
 
-	describeRes chan []byte
+	describeRes chan describeRes
 	events      chan clientEvent // only if state = Play and gortsplib.StreamProtocol = TCP
 	done        chan struct{}
 }
 
-func newServerClient(p *program, nconn net.Conn) *client {
+func newClient(p *program, nconn net.Conn) *client {
 	c := &client{
 		p: p,
 		conn: gortsplib.NewConnServer(gortsplib.ConnServerConf{
@@ -125,12 +130,12 @@ func (c *client) zone() string {
 }
 
 func (c *client) run() {
-	var runOnConnectCmd *exec.Cmd
+	var onConnectCmd *exec.Cmd
 	if c.p.conf.RunOnConnect != "" {
-		runOnConnectCmd = exec.Command("/bin/sh", "-c", c.p.conf.RunOnConnect)
-		runOnConnectCmd.Stdout = os.Stdout
-		runOnConnectCmd.Stderr = os.Stderr
-		err := runOnConnectCmd.Start()
+		onConnectCmd = exec.Command("/bin/sh", "-c", c.p.conf.RunOnConnect)
+		onConnectCmd.Stdout = os.Stdout
+		onConnectCmd.Stderr = os.Stderr
+		err := onConnectCmd.Start()
 		if err != nil {
 			c.log("ERR: %s", err)
 		}
@@ -158,9 +163,9 @@ outer:
 
 	c.conn.NetConn().Close() // close socket in case it has not been closed yet
 
-	if runOnConnectCmd != nil {
-		runOnConnectCmd.Process.Signal(os.Interrupt)
-		runOnConnectCmd.Wait()
+	if onConnectCmd != nil {
+		onConnectCmd.Process.Signal(os.Interrupt)
+		onConnectCmd.Wait()
 	}
 
 	close(c.done) // close() never blocks
@@ -311,14 +316,14 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 			return false
 		}
 
-		pconf := c.p.findConfForPath(path)
-		if pconf == nil {
+		confp := c.p.findConfForPath(path)
+		if confp == nil {
 			c.writeResError(req, gortsplib.StatusBadRequest,
 				fmt.Errorf("unable to find a valid configuration for path '%s'", path))
 			return false
 		}
 
-		err := c.authenticate(pconf.readIpsParsed, pconf.ReadUser, pconf.ReadPass, req)
+		err := c.authenticate(confp.readIpsParsed, confp.ReadUser, confp.ReadPass, req)
 		if err != nil {
 			if err == errAuthCritical {
 				return false
@@ -326,11 +331,11 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 			return true
 		}
 
-		c.describeRes = make(chan []byte)
+		c.describeRes = make(chan describeRes)
 		c.p.events <- programEventClientDescribe{c, path}
-		sdp := <-c.describeRes
-		if sdp == nil {
-			c.writeResError(req, gortsplib.StatusNotFound, fmt.Errorf("no one is publishing on path '%s'", path))
+		describeRes := <-c.describeRes
+		if describeRes.err != nil {
+			c.writeResError(req, gortsplib.StatusNotFound, describeRes.err)
 			return false
 		}
 
@@ -341,7 +346,7 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 				"Content-Base": gortsplib.HeaderValue{req.Url.String() + "/"},
 				"Content-Type": gortsplib.HeaderValue{"application/sdp"},
 			},
-			Content: sdp,
+			Content: describeRes.sdp,
 		})
 		return true
 
@@ -357,14 +362,14 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 			return false
 		}
 
-		pconf := c.p.findConfForPath(path)
-		if pconf == nil {
+		confp := c.p.findConfForPath(path)
+		if confp == nil {
 			c.writeResError(req, gortsplib.StatusBadRequest,
 				fmt.Errorf("unable to find a valid configuration for path '%s'", path))
 			return false
 		}
 
-		err := c.authenticate(pconf.publishIpsParsed, pconf.PublishUser, pconf.PublishPass, req)
+		err := c.authenticate(confp.publishIpsParsed, confp.PublishUser, confp.PublishPass, req)
 		if err != nil {
 			if err == errAuthCritical {
 				return false
@@ -435,14 +440,14 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 		switch c.state {
 		// play
 		case clientStateInitial, clientStatePrePlay:
-			pconf := c.p.findConfForPath(path)
-			if pconf == nil {
+			confp := c.p.findConfForPath(path)
+			if confp == nil {
 				c.writeResError(req, gortsplib.StatusBadRequest,
 					fmt.Errorf("unable to find a valid configuration for path '%s'", path))
 				return false
 			}
 
-			err := c.authenticate(pconf.readIpsParsed, pconf.ReadUser, pconf.ReadPass, req)
+			err := c.authenticate(confp.readIpsParsed, confp.ReadUser, confp.ReadPass, req)
 			if err != nil {
 				if err == errAuthCritical {
 					return false
@@ -473,7 +478,7 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 					return false
 				}
 
-				if c.path != "" && path != c.path {
+				if c.pathId != "" && path != c.pathId {
 					c.writeResError(req, gortsplib.StatusBadRequest, fmt.Errorf("path has changed"))
 					return false
 				}
@@ -513,7 +518,7 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 					return false
 				}
 
-				if c.path != "" && path != c.path {
+				if c.pathId != "" && path != c.pathId {
 					c.writeResError(req, gortsplib.StatusBadRequest, fmt.Errorf("path has changed"))
 					return false
 				}
@@ -559,8 +564,8 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 				return false
 			}
 
-			// after ANNOUNCE, c.path is already set
-			if path != c.path {
+			// after ANNOUNCE, c.pathId is already set
+			if path != c.pathId {
 				c.writeResError(req, gortsplib.StatusBadRequest, fmt.Errorf("path has changed"))
 				return false
 			}
@@ -593,7 +598,7 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 					return false
 				}
 
-				if len(c.streamTracks) >= len(c.p.paths[c.path].publisherSdpParsed.MediaDescriptions) {
+				if len(c.streamTracks) >= len(c.p.paths[c.pathId].publisherSdpParsed.MediaDescriptions) {
 					c.writeResError(req, gortsplib.StatusBadRequest, fmt.Errorf("all the tracks have already been setup"))
 					return false
 				}
@@ -645,7 +650,7 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 					return false
 				}
 
-				if len(c.streamTracks) >= len(c.p.paths[c.path].publisherSdpParsed.MediaDescriptions) {
+				if len(c.streamTracks) >= len(c.p.paths[c.pathId].publisherSdpParsed.MediaDescriptions) {
 					c.writeResError(req, gortsplib.StatusBadRequest, fmt.Errorf("all the tracks have already been setup"))
 					return false
 				}
@@ -689,7 +694,7 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 			return false
 		}
 
-		if path != c.path {
+		if path != c.pathId {
 			c.writeResError(req, gortsplib.StatusBadRequest, fmt.Errorf("path has changed"))
 			return false
 		}
@@ -724,12 +729,12 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 			return false
 		}
 
-		if path != c.path {
+		if path != c.pathId {
 			c.writeResError(req, gortsplib.StatusBadRequest, fmt.Errorf("path has changed"))
 			return false
 		}
 
-		if len(c.streamTracks) != len(c.p.paths[c.path].publisherSdpParsed.MediaDescriptions) {
+		if len(c.streamTracks) != len(c.p.paths[c.pathId].publisherSdpParsed.MediaDescriptions) {
 			c.writeResError(req, gortsplib.StatusBadRequest, fmt.Errorf("not all tracks have been setup"))
 			return false
 		}
@@ -756,7 +761,7 @@ func (c *client) handleRequest(req *gortsplib.Request) bool {
 }
 
 func (c *client) runPlay(path string) {
-	pconf := c.p.findConfForPath(path)
+	confp := c.p.findConfForPath(path)
 
 	if c.streamProtocol == gortsplib.StreamProtocolTcp {
 		c.writeBuf = newDoubleBuffer(clientTcpWriteBufferSize)
@@ -767,19 +772,19 @@ func (c *client) runPlay(path string) {
 	c.p.events <- programEventClientPlay2{done, c}
 	<-done
 
-	c.log("is receiving on path '%s', %d %s via %s", c.path, len(c.streamTracks), func() string {
+	c.log("is receiving on path '%s', %d %s via %s", c.pathId, len(c.streamTracks), func() string {
 		if len(c.streamTracks) == 1 {
 			return "track"
 		}
 		return "tracks"
 	}(), c.streamProtocol)
 
-	var runOnReadCmd *exec.Cmd
-	if pconf.RunOnRead != "" {
-		runOnReadCmd = exec.Command("/bin/sh", "-c", pconf.RunOnRead)
-		runOnReadCmd.Stdout = os.Stdout
-		runOnReadCmd.Stderr = os.Stderr
-		err := runOnReadCmd.Start()
+	var onReadCmd *exec.Cmd
+	if confp.RunOnRead != "" {
+		onReadCmd = exec.Command("/bin/sh", "-c", confp.RunOnRead)
+		onReadCmd.Stdout = os.Stdout
+		onReadCmd.Stderr = os.Stderr
+		err := onReadCmd.Start()
 		if err != nil {
 			c.log("ERR: %s", err)
 		}
@@ -848,14 +853,14 @@ func (c *client) runPlay(path string) {
 		close(c.events)
 	}
 
-	if runOnReadCmd != nil {
-		runOnReadCmd.Process.Signal(os.Interrupt)
-		runOnReadCmd.Wait()
+	if onReadCmd != nil {
+		onReadCmd.Process.Signal(os.Interrupt)
+		onReadCmd.Wait()
 	}
 }
 
 func (c *client) runRecord(path string) {
-	pconf := c.p.findConfForPath(path)
+	confp := c.p.findConfForPath(path)
 
 	c.rtcpReceivers = make([]*gortsplib.RtcpReceiver, len(c.streamTracks))
 	for trackId := range c.streamTracks {
@@ -866,19 +871,19 @@ func (c *client) runRecord(path string) {
 	c.p.events <- programEventClientRecord{done, c}
 	<-done
 
-	c.log("is publishing on path '%s', %d %s via %s", c.path, len(c.streamTracks), func() string {
+	c.log("is publishing on path '%s', %d %s via %s", c.pathId, len(c.streamTracks), func() string {
 		if len(c.streamTracks) == 1 {
 			return "track"
 		}
 		return "tracks"
 	}(), c.streamProtocol)
 
-	var runOnPublishCmd *exec.Cmd
-	if pconf.RunOnPublish != "" {
-		runOnPublishCmd = exec.Command("/bin/sh", "-c", pconf.RunOnPublish)
-		runOnPublishCmd.Stdout = os.Stdout
-		runOnPublishCmd.Stderr = os.Stderr
-		err := runOnPublishCmd.Start()
+	var onPublishCmd *exec.Cmd
+	if confp.RunOnPublish != "" {
+		onPublishCmd = exec.Command("/bin/sh", "-c", confp.RunOnPublish)
+		onPublishCmd.Stdout = os.Stdout
+		onPublishCmd.Stderr = os.Stderr
+		err := onPublishCmd.Start()
 		if err != nil {
 			c.log("ERR: %s", err)
 		}
@@ -967,7 +972,7 @@ func (c *client) runRecord(path string) {
 
 					c.rtcpReceivers[frame.TrackId].OnFrame(frame.StreamType, frame.Content)
 					c.p.events <- programEventClientFrameTcp{
-						c.path,
+						c.pathId,
 						frame.TrackId,
 						frame.StreamType,
 						frame.Content,
@@ -1017,8 +1022,8 @@ func (c *client) runRecord(path string) {
 		c.rtcpReceivers[trackId].Close()
 	}
 
-	if runOnPublishCmd != nil {
-		runOnPublishCmd.Process.Signal(os.Interrupt)
-		runOnPublishCmd.Wait()
+	if onPublishCmd != nil {
+		onPublishCmd.Process.Signal(os.Interrupt)
+		onPublishCmd.Wait()
 	}
 }
diff --git a/conf.go b/conf.go
index 6ae3fdc5..f79e1fcc 100644
--- a/conf.go
+++ b/conf.go
@@ -26,6 +26,7 @@ type confPath struct {
 	ReadPass             string   `yaml:"readPass"`
 	ReadIps              []string `yaml:"readIps"`
 	readIpsParsed        []interface{}
+	RunOnDemand          string `yaml:"runOnDemand"`
 	RunOnPublish         string `yaml:"runOnPublish"`
 	RunOnRead            string `yaml:"runOnRead"`
 }
@@ -148,91 +149,95 @@ func loadConf(fpath string, stdin io.Reader) (*conf, error) {
 		}
 	}
 
-	for path, pconf := range conf.Paths {
-		if pconf == nil {
+	for path, confp := range conf.Paths {
+		if confp == nil {
 			conf.Paths[path] = &confPath{}
-			pconf = conf.Paths[path]
+			confp = conf.Paths[path]
 		}
 
-		if pconf.Source == "" {
-			pconf.Source = "record"
+		if confp.Source == "" {
+			confp.Source = "record"
 		}
 
-		if pconf.PublishUser != "" {
-			if !regexp.MustCompile("^[a-zA-Z0-9]+$").MatchString(pconf.PublishUser) {
-				return nil, fmt.Errorf("publish username must be alphanumeric")
-			}
-		}
-		if pconf.PublishPass != "" {
-			if !regexp.MustCompile("^[a-zA-Z0-9]+$").MatchString(pconf.PublishPass) {
-				return nil, fmt.Errorf("publish password must be alphanumeric")
-			}
-		}
-		pconf.publishIpsParsed, err = parseIpCidrList(pconf.PublishIps)
-		if err != nil {
-			return nil, err
-		}
-
-		if pconf.ReadUser != "" && pconf.ReadPass == "" || pconf.ReadUser == "" && pconf.ReadPass != "" {
-			return nil, fmt.Errorf("read username and password must be both filled")
-		}
-		if pconf.ReadUser != "" {
-			if !regexp.MustCompile("^[a-zA-Z0-9]+$").MatchString(pconf.ReadUser) {
-				return nil, fmt.Errorf("read username must be alphanumeric")
-			}
-		}
-		if pconf.ReadPass != "" {
-			if !regexp.MustCompile("^[a-zA-Z0-9]+$").MatchString(pconf.ReadPass) {
-				return nil, fmt.Errorf("read password must be alphanumeric")
-			}
-		}
-		if pconf.ReadUser != "" && pconf.ReadPass == "" || pconf.ReadUser == "" && pconf.ReadPass != "" {
-			return nil, fmt.Errorf("read username and password must be both filled")
-		}
-		pconf.readIpsParsed, err = parseIpCidrList(pconf.ReadIps)
-		if err != nil {
-			return nil, err
-		}
-
-		if pconf.Source != "record" {
+		if confp.Source != "record" {
 			if path == "all" {
 				return nil, fmt.Errorf("path 'all' cannot have a RTSP source")
 			}
 
-			if pconf.SourceProtocol == "" {
-				pconf.SourceProtocol = "udp"
+			if confp.SourceProtocol == "" {
+				confp.SourceProtocol = "udp"
 			}
 
-			pconf.sourceUrl, err = url.Parse(pconf.Source)
+			confp.sourceUrl, err = url.Parse(confp.Source)
 			if err != nil {
-				return nil, fmt.Errorf("'%s' is not a valid RTSP url", pconf.Source)
+				return nil, fmt.Errorf("'%s' is not a valid RTSP url", confp.Source)
 			}
-			if pconf.sourceUrl.Scheme != "rtsp" {
-				return nil, fmt.Errorf("'%s' is not a valid RTSP url", pconf.Source)
+			if confp.sourceUrl.Scheme != "rtsp" {
+				return nil, fmt.Errorf("'%s' is not a valid RTSP url", confp.Source)
 			}
-			if pconf.sourceUrl.Port() == "" {
-				pconf.sourceUrl.Host += ":554"
+			if confp.sourceUrl.Port() == "" {
+				confp.sourceUrl.Host += ":554"
 			}
-			if pconf.sourceUrl.User != nil {
-				pass, _ := pconf.sourceUrl.User.Password()
-				user := pconf.sourceUrl.User.Username()
+			if confp.sourceUrl.User != nil {
+				pass, _ := confp.sourceUrl.User.Password()
+				user := confp.sourceUrl.User.Username()
 				if user != "" && pass == "" ||
 					user == "" && pass != "" {
 					fmt.Errorf("username and password must be both provided")
 				}
 			}
 
-			switch pconf.SourceProtocol {
+			switch confp.SourceProtocol {
 			case "udp":
-				pconf.sourceProtocolParsed = gortsplib.StreamProtocolUdp
+				confp.sourceProtocolParsed = gortsplib.StreamProtocolUdp
 
 			case "tcp":
-				pconf.sourceProtocolParsed = gortsplib.StreamProtocolTcp
+				confp.sourceProtocolParsed = gortsplib.StreamProtocolTcp
 
 			default:
-				return nil, fmt.Errorf("unsupported protocol '%s'", pconf.SourceProtocol)
+				return nil, fmt.Errorf("unsupported protocol '%s'", confp.SourceProtocol)
 			}
 		}
+
+		if confp.PublishUser != "" {
+			if !regexp.MustCompile("^[a-zA-Z0-9]+$").MatchString(confp.PublishUser) {
+				return nil, fmt.Errorf("publish username must be alphanumeric")
+			}
+		}
+		if confp.PublishPass != "" {
+			if !regexp.MustCompile("^[a-zA-Z0-9]+$").MatchString(confp.PublishPass) {
+				return nil, fmt.Errorf("publish password must be alphanumeric")
+			}
+		}
+		confp.publishIpsParsed, err = parseIpCidrList(confp.PublishIps)
+		if err != nil {
+			return nil, err
+		}
+
+		if confp.ReadUser != "" && confp.ReadPass == "" || confp.ReadUser == "" && confp.ReadPass != "" {
+			return nil, fmt.Errorf("read username and password must be both filled")
+		}
+		if confp.ReadUser != "" {
+			if !regexp.MustCompile("^[a-zA-Z0-9]+$").MatchString(confp.ReadUser) {
+				return nil, fmt.Errorf("read username must be alphanumeric")
+			}
+		}
+		if confp.ReadPass != "" {
+			if !regexp.MustCompile("^[a-zA-Z0-9]+$").MatchString(confp.ReadPass) {
+				return nil, fmt.Errorf("read password must be alphanumeric")
+			}
+		}
+		if confp.ReadUser != "" && confp.ReadPass == "" || confp.ReadUser == "" && confp.ReadPass != "" {
+			return nil, fmt.Errorf("read username and password must be both filled")
+		}
+		confp.readIpsParsed, err = parseIpCidrList(confp.ReadIps)
+		if err != nil {
+			return nil, err
+		}
+
+		if confp.RunOnDemand != "" && path == "all" {
+			return nil, fmt.Errorf("option 'runOnDemand' cannot be used in path 'all'")
+		}
 	}
 
 	return conf, nil
diff --git a/main.go b/main.go
index 6c390f27..45780c37 100644
--- a/main.go
+++ b/main.go
@@ -145,12 +145,6 @@ type programEventSourceFrame struct {
 
 func (programEventSourceFrame) isProgramEvent() {}
 
-type programEventSourceReset struct {
-	source *source
-}
-
-func (programEventSourceReset) isProgramEvent() {}
-
 type programEventTerminate struct{}
 
 func (programEventTerminate) isProgramEvent() {}
@@ -197,11 +191,17 @@ func newProgram(args []string, stdin io.Reader) (*program, error) {
 		done:    make(chan struct{}),
 	}
 
-	for path, pconf := range conf.Paths {
-		if pconf.Source != "record" {
-			s := newSource(p, path, pconf)
+	for path, confp := range conf.Paths {
+		if path == "all" {
+			continue
+		}
+
+		newPath(p, path, confp, true)
+
+		if confp.Source != "record" {
+			s := newSource(p, path, confp)
 			p.sources = append(p.sources, s)
-			p.paths[path] = newPath(p, path, s)
+			p.paths[path].publisher = s
 		}
 	}
 
@@ -265,21 +265,21 @@ outer:
 		case rawEvt := <-p.events:
 			switch evt := rawEvt.(type) {
 			case programEventClientNew:
-				c := newServerClient(p, evt.nconn)
+				c := newClient(p, evt.nconn)
 				p.clients[c] = struct{}{}
 				c.log("connected")
 
 			case programEventClientClose:
 				delete(p.clients, evt.client)
 
-				if evt.client.path != "" {
-					if path, ok := p.paths[evt.client.path]; ok {
-						// if this is a publisher
+				if evt.client.pathId != "" {
+					if path, ok := p.paths[evt.client.pathId]; ok {
 						if path.publisher == evt.client {
-							path.publisherReset()
+							path.publisherRemove()
 
-							// delete the path
-							delete(p.paths, evt.client.path)
+							if !path.permanent {
+								delete(p.paths, evt.client.pathId)
+							}
 						}
 					}
 				}
@@ -289,35 +289,30 @@ outer:
 
 			case programEventClientDescribe:
 				path, ok := p.paths[evt.path]
-
-				// no path: return 404
 				if !ok {
-					evt.client.describeRes <- nil
+					evt.client.describeRes <- describeRes{nil, fmt.Errorf("no one is publishing on path '%s'", evt.path)}
 					continue
 				}
 
-				sdpText, wait := path.describe()
-
-				if wait {
-					evt.client.path = evt.path
-					evt.client.state = clientStateWaitingDescription
-					continue
-				}
-
-				evt.client.describeRes <- sdpText
+				path.describe(evt.client)
 
 			case programEventClientAnnounce:
-				_, ok := p.paths[evt.path]
-				if ok {
-					evt.res <- fmt.Errorf("someone is already publishing on path '%s'", evt.path)
-					continue
+				if path, ok := p.paths[evt.path]; ok {
+					if path.publisher != nil {
+						evt.res <- fmt.Errorf("someone is already publishing on path '%s'", evt.path)
+						continue
+					}
+
+				} else {
+					newPath(p, evt.path, p.findConfForPath(evt.path), false)
 				}
 
-				evt.client.path = evt.path
-				evt.client.state = clientStateAnnounce
-				p.paths[evt.path] = newPath(p, evt.path, evt.client)
+				p.paths[evt.path].publisher = evt.client
 				p.paths[evt.path].publisherSdpText = evt.sdpText
 				p.paths[evt.path].publisherSdpParsed = evt.sdpParsed
+
+				evt.client.pathId = evt.path
+				evt.client.state = clientStateAnnounce
 				evt.res <- nil
 
 			case programEventClientSetupPlay:
@@ -332,7 +327,7 @@ outer:
 					continue
 				}
 
-				evt.client.path = evt.path
+				evt.client.pathId = evt.path
 				evt.client.streamProtocol = evt.protocol
 				evt.client.streamTracks = append(evt.client.streamTracks, &clientTrack{
 					rtpPort:  evt.rtpPort,
@@ -351,9 +346,9 @@ outer:
 				evt.res <- nil
 
 			case programEventClientPlay1:
-				path, ok := p.paths[evt.client.path]
+				path, ok := p.paths[evt.client.pathId]
 				if !ok || !path.publisherReady {
-					evt.res <- fmt.Errorf("no one is publishing on path '%s'", evt.client.path)
+					evt.res <- fmt.Errorf("no one is publishing on path '%s'", evt.client.pathId)
 					continue
 				}
 
@@ -377,13 +372,13 @@ outer:
 			case programEventClientRecord:
 				p.publisherCount += 1
 				evt.client.state = clientStateRecord
-				p.paths[evt.client.path].publisherSetReady()
+				p.paths[evt.client.pathId].publisherSetReady()
 				close(evt.done)
 
 			case programEventClientRecordStop:
 				p.publisherCount -= 1
 				evt.client.state = clientStatePreRecord
-				p.paths[evt.client.path].publisherSetNotReady()
+				p.paths[evt.client.pathId].publisherSetNotReady()
 				close(evt.done)
 
 			case programEventClientFrameUdp:
@@ -393,24 +388,21 @@ outer:
 				}
 
 				client.rtcpReceivers[trackId].OnFrame(evt.streamType, evt.buf)
-				p.forwardFrame(client.path, trackId, evt.streamType, evt.buf)
+				p.forwardFrame(client.pathId, trackId, evt.streamType, evt.buf)
 
 			case programEventClientFrameTcp:
 				p.forwardFrame(evt.path, evt.trackId, evt.streamType, evt.buf)
 
 			case programEventSourceReady:
 				evt.source.log("ready")
-				p.paths[evt.source.path].publisherSetReady()
+				p.paths[evt.source.pathId].publisherSetReady()
 
 			case programEventSourceNotReady:
 				evt.source.log("not ready")
-				p.paths[evt.source.path].publisherSetNotReady()
+				p.paths[evt.source.pathId].publisherSetNotReady()
 
 			case programEventSourceFrame:
-				p.forwardFrame(evt.source.path, evt.trackId, evt.streamType, evt.buf)
-
-			case programEventSourceReset:
-				p.paths[evt.source.path].publisherReset()
+				p.forwardFrame(evt.source.pathId, evt.trackId, evt.streamType, evt.buf)
 
 			case programEventTerminate:
 				break outer
@@ -425,7 +417,7 @@ outer:
 				close(evt.done)
 
 			case programEventClientDescribe:
-				evt.client.describeRes <- nil
+				evt.client.describeRes <- describeRes{nil, fmt.Errorf("terminated")}
 
 			case programEventClientAnnounce:
 				evt.res <- fmt.Errorf("terminated")
@@ -478,12 +470,12 @@ func (p *program) close() {
 }
 
 func (p *program) findConfForPath(path string) *confPath {
-	if pconf, ok := p.conf.Paths[path]; ok {
-		return pconf
+	if confp, ok := p.conf.Paths[path]; ok {
+		return confp
 	}
 
-	if pconf, ok := p.conf.Paths["all"]; ok {
-		return pconf
+	if confp, ok := p.conf.Paths["all"]; ok {
+		return confp
 	}
 
 	return nil
@@ -518,35 +510,35 @@ func (p *program) findClientPublisher(addr *net.UDPAddr, streamType gortsplib.St
 }
 
 func (p *program) forwardFrame(path string, trackId int, streamType gortsplib.StreamType, frame []byte) {
-	for client := range p.clients {
-		if client.path == path && client.state == clientStatePlay {
-			if client.streamProtocol == gortsplib.StreamProtocolUdp {
+	for c := range p.clients {
+		if c.pathId == path && c.state == clientStatePlay {
+			if c.streamProtocol == gortsplib.StreamProtocolUdp {
 				if streamType == gortsplib.StreamTypeRtp {
 					p.rtpl.write(&udpAddrBufPair{
 						addr: &net.UDPAddr{
-							IP:   client.ip(),
-							Zone: client.zone(),
-							Port: client.streamTracks[trackId].rtpPort,
+							IP:   c.ip(),
+							Zone: c.zone(),
+							Port: c.streamTracks[trackId].rtpPort,
 						},
 						buf: frame,
 					})
 				} else {
 					p.rtcpl.write(&udpAddrBufPair{
 						addr: &net.UDPAddr{
-							IP:   client.ip(),
-							Zone: client.zone(),
-							Port: client.streamTracks[trackId].rtcpPort,
+							IP:   c.ip(),
+							Zone: c.zone(),
+							Port: c.streamTracks[trackId].rtcpPort,
 						},
 						buf: frame,
 					})
 				}
 
 			} else {
-				buf := client.writeBuf.swap()
+				buf := c.writeBuf.swap()
 				buf = buf[:len(frame)]
 				copy(buf, frame)
 
-				client.events <- clientEventFrameTcp{
+				c.events <- clientEventFrameTcp{
 					frame: &gortsplib.InterleavedFrame{
 						TrackId:    trackId,
 						StreamType: streamType,
diff --git a/path.go b/path.go
index 862ebd93..4ac50917 100644
--- a/path.go
+++ b/path.go
@@ -1,6 +1,9 @@
 package main
 
 import (
+	"fmt"
+	"os"
+	"os/exec"
 	"time"
 
 	"github.com/aler9/sdp/v3"
@@ -14,97 +17,182 @@ type publisher interface {
 type path struct {
 	p                  *program
 	id                 string
+	confp              *confPath
+	permanent          bool
 	publisher          publisher
 	publisherReady     bool
 	publisherSdpText   []byte
 	publisherSdpParsed *sdp.SessionDescription
 	lastRequested      time.Time
+	lastActivation     time.Time
+	onDemandCmd        *exec.Cmd
 }
 
-func newPath(p *program, id string, publisher publisher) *path {
-	return &path{
+func newPath(p *program, id string, confp *confPath, permanent bool) {
+	pa := &path{
 		p:         p,
 		id:        id,
-		publisher: publisher,
+		confp:     confp,
+		permanent: permanent,
 	}
+
+	p.paths[id] = pa
 }
 
-func (p *path) check() {
-	hasClients := func() bool {
-		for c := range p.p.clients {
-			if c.path == p.id {
+func (pa *path) check() {
+	hasClientsWaitingDescribe := func() bool {
+		for c := range pa.p.clients {
+			if c.state == clientStateWaitingDescription && c.pathId == pa.id {
 				return true
 			}
 		}
 		return false
 	}()
-	source, publisherIsSource := p.publisher.(*source)
 
-	// stop source if needed
-	if !hasClients &&
-		publisherIsSource &&
-		source.state == sourceStateRunning &&
-		time.Since(p.lastRequested) >= 10*time.Second {
-		source.log("stopping due to inactivity")
-		source.state = sourceStateStopped
-		source.events <- sourceEventApplyState{source.state}
+	// reply to DESCRIBE requests if they are in timeout
+	if hasClientsWaitingDescribe &&
+		time.Since(pa.lastActivation) >= 5*time.Second {
+		for c := range pa.p.clients {
+			if c.state == clientStateWaitingDescription &&
+				c.pathId == pa.id {
+				c.pathId = ""
+				c.state = clientStateInitial
+				c.describeRes <- describeRes{nil, fmt.Errorf("publisher of path '%s' has timed out", pa.id)}
+			}
+		}
+
+		// perform actions below in next run
+		return
+	}
+
+	if source, ok := pa.publisher.(*source); ok {
+		if source.state == sourceStateRunning {
+			hasClients := func() bool {
+				for c := range pa.p.clients {
+					if c.pathId == pa.id {
+						return true
+					}
+				}
+				return false
+			}()
+
+			// stop source if needed
+			if !hasClients &&
+				time.Since(pa.lastRequested) >= 10*time.Second {
+				source.log("stopping since we're not requested anymore")
+				source.state = sourceStateStopped
+				source.events <- sourceEventApplyState{source.state}
+			}
+		}
+
+	} else {
+		if pa.onDemandCmd != nil {
+			hasClientReaders := func() bool {
+				for c := range pa.p.clients {
+					if c.pathId == pa.id && c != pa.publisher {
+						return true
+					}
+				}
+				return false
+			}()
+
+			// stop on demand command if needed
+			if !hasClientReaders &&
+				time.Since(pa.lastRequested) >= 10*time.Second {
+				pa.p.log("stopping on demand command since it is not requested anymore")
+
+				pa.onDemandCmd.Process.Signal(os.Interrupt)
+				pa.onDemandCmd.Wait()
+				pa.onDemandCmd = nil
+			}
+		}
 	}
 }
 
-func (p *path) describe() ([]byte, bool) {
-	p.lastRequested = time.Now()
+func (pa *path) describe(client *client) {
+	pa.lastRequested = time.Now()
 
-	// publisher was found but is not ready: wait
-	if !p.publisherReady {
+	// publisher not found
+	if pa.publisher == nil {
+		if pa.confp.RunOnDemand != "" {
+			if pa.onDemandCmd == nil {
+				pa.p.log("starting on demand command")
+
+				pa.lastActivation = time.Now()
+				pa.onDemandCmd = exec.Command("/bin/sh", "-c", pa.confp.RunOnDemand)
+				pa.onDemandCmd.Stdout = os.Stdout
+				pa.onDemandCmd.Stderr = os.Stderr
+				err := pa.onDemandCmd.Start()
+				if err != nil {
+					pa.p.log("ERR: %s", err)
+				}
+			}
+
+			client.pathId = pa.id
+			client.state = clientStateWaitingDescription
+			return
+
+		} else {
+			client.describeRes <- describeRes{nil, fmt.Errorf("no one is publishing on path '%s'", pa.id)}
+			return
+		}
+	}
+
+	// publisher was found but is not ready: put the client on hold
+	if !pa.publisherReady {
 		// start source if needed
-		if source, ok := p.publisher.(*source); ok && source.state == sourceStateStopped {
+		if source, ok := pa.publisher.(*source); ok && source.state == sourceStateStopped {
 			source.log("starting on demand")
+			pa.lastActivation = time.Now()
 			source.state = sourceStateRunning
 			source.events <- sourceEventApplyState{source.state}
 		}
 
-		return nil, true
+		client.pathId = pa.id
+		client.state = clientStateWaitingDescription
+		return
 	}
 
 	// publisher was found and is ready
-	return p.publisherSdpText, false
+	client.describeRes <- describeRes{pa.publisherSdpText, nil}
 }
 
-func (p *path) publisherSetReady() {
-	p.publisherReady = true
+func (pa *path) publisherRemove() {
+	for c := range pa.p.clients {
+		if c.state == clientStateWaitingDescription &&
+			c.pathId == pa.id {
+			c.pathId = ""
+			c.state = clientStateInitial
+			c.describeRes <- describeRes{nil, fmt.Errorf("publisher of path '%s' is not available anymore", pa.id)}
+		}
+	}
+
+	pa.publisher = nil
+}
+
+func (pa *path) publisherSetReady() {
+	pa.publisherReady = true
 
 	// reply to all clients that are waiting for a description
-	for c := range p.p.clients {
+	for c := range pa.p.clients {
 		if c.state == clientStateWaitingDescription &&
-			c.path == p.id {
-			c.path = ""
+			c.pathId == pa.id {
+			c.pathId = ""
 			c.state = clientStateInitial
-			c.describeRes <- p.publisherSdpText
+			c.describeRes <- describeRes{pa.publisherSdpText, nil}
 		}
 	}
 }
 
-func (p *path) publisherSetNotReady() {
-	p.publisherReady = false
+func (pa *path) publisherSetNotReady() {
+	pa.publisherReady = false
 
 	// close all clients that are reading
-	for c := range p.p.clients {
+	for c := range pa.p.clients {
 		if c.state != clientStateWaitingDescription &&
-			c != p.publisher &&
-			c.path == p.id {
+			c != pa.publisher &&
+			c.pathId == pa.id {
 			c.conn.NetConn().Close()
 		}
 	}
 }
-
-func (p *path) publisherReset() {
-	// reply to all clients that were waiting for a description
-	for oc := range p.p.clients {
-		if oc.state == clientStateWaitingDescription &&
-			oc.path == p.id {
-			oc.path = ""
-			oc.state = clientStateInitial
-			oc.describeRes <- nil
-		}
-	}
-}
diff --git a/rtsp-simple-server.yml b/rtsp-simple-server.yml
index 9c093934..a99bcd52 100644
--- a/rtsp-simple-server.yml
+++ b/rtsp-simple-server.yml
@@ -48,6 +48,11 @@ paths:
     # IPs or networks (x.x.x.x/24) allowed to read
     readIps: []
 
+    # command to run when this path is requested.
+    # This can be used, for example, to publish a stream on demand.
+    # This is terminated with SIGINT when a client stops publishing.
+    runOnDemand:
+
     # command to run when a client starts publishing.
     # This is terminated with SIGINT when a client stops publishing.
     runOnPublish:
diff --git a/source.go b/source.go
index 79a0e474..9aa7e7d0 100644
--- a/source.go
+++ b/source.go
@@ -39,8 +39,8 @@ func (sourceEventTerminate) isSourceEvent() {}
 
 type source struct {
 	p      *program
-	path   string
-	pconf  *confPath
+	pathId string
+	confp  *confPath
 	state  sourceState
 	tracks []*gortsplib.Track
 
@@ -48,16 +48,16 @@ type source struct {
 	done   chan struct{}
 }
 
-func newSource(p *program, path string, pconf *confPath) *source {
+func newSource(p *program, pathId string, confp *confPath) *source {
 	s := &source{
 		p:      p,
-		path:   path,
-		pconf:  pconf,
+		pathId: pathId,
+		confp:  confp,
 		events: make(chan sourceEvent),
 		done:   make(chan struct{}),
 	}
 
-	if pconf.SourceOnDemand {
+	if confp.SourceOnDemand {
 		s.state = sourceStateStopped
 	} else {
 		s.state = sourceStateRunning
@@ -67,7 +67,7 @@ func newSource(p *program, path string, pconf *confPath) *source {
 }
 
 func (s *source) log(format string, args ...interface{}) {
-	s.p.log("[source "+s.path+"] "+format, args...)
+	s.p.log("[source "+s.pathId+"] "+format, args...)
 }
 
 func (s *source) isPublisher() {}
@@ -121,23 +121,24 @@ func (s *source) do(terminate chan struct{}, done chan struct{}) {
 	defer close(done)
 
 	for {
-		ok := s.doInner(terminate)
-		if !ok {
-			break
-		}
+		ok := func() bool {
+			ok := s.doInner(terminate)
+			if !ok {
+				return false
+			}
 
-		s.p.events <- programEventSourceReset{s}
-
-		if !func() bool {
 			t := time.NewTimer(sourceRetryInterval)
 			defer t.Stop()
+
 			select {
 			case <-terminate:
 				return false
 			case <-t.C:
-				return true
 			}
-		}() {
+
+			return true
+		}()
+		if !ok {
 			break
 		}
 	}
@@ -151,7 +152,7 @@ func (s *source) doInner(terminate chan struct{}) bool {
 	dialDone := make(chan struct{})
 	go func() {
 		conn, err = gortsplib.NewConnClient(gortsplib.ConnClientConf{
-			Host:         s.pconf.sourceUrl.Host,
+			Host:         s.confp.sourceUrl.Host,
 			ReadTimeout:  s.p.conf.ReadTimeout,
 			WriteTimeout: s.p.conf.WriteTimeout,
 		})
@@ -171,13 +172,13 @@ func (s *source) doInner(terminate chan struct{}) bool {
 
 	defer conn.Close()
 
-	_, err = conn.Options(s.pconf.sourceUrl)
+	_, err = conn.Options(s.confp.sourceUrl)
 	if err != nil {
 		s.log("ERR: %s", err)
 		return true
 	}
 
-	tracks, _, err := conn.Describe(s.pconf.sourceUrl)
+	tracks, _, err := conn.Describe(s.confp.sourceUrl)
 	if err != nil {
 		s.log("ERR: %s", err)
 		return true
@@ -187,10 +188,10 @@ func (s *source) doInner(terminate chan struct{}) bool {
 	serverSdpParsed, serverSdpText := sdpForServer(tracks)
 
 	s.tracks = tracks
-	s.p.paths[s.path].publisherSdpText = serverSdpText
-	s.p.paths[s.path].publisherSdpParsed = serverSdpParsed
+	s.p.paths[s.pathId].publisherSdpText = serverSdpText
+	s.p.paths[s.pathId].publisherSdpParsed = serverSdpParsed
 
-	if s.pconf.sourceProtocolParsed == gortsplib.StreamProtocolUdp {
+	if s.confp.sourceProtocolParsed == gortsplib.StreamProtocolUdp {
 		return s.runUdp(terminate, conn)
 	} else {
 		return s.runTcp(terminate, conn)
@@ -215,7 +216,7 @@ func (s *source) runUdp(terminate chan struct{}, conn *gortsplib.ConnClient) boo
 			rtpPort := (rand.Intn((65535-10000)/2) * 2) + 10000
 			rtcpPort := rtpPort + 1
 
-			rtpl, rtcpl, _, err = conn.SetupUdp(s.pconf.sourceUrl, track, rtpPort, rtcpPort)
+			rtpl, rtcpl, _, err = conn.SetupUdp(s.confp.sourceUrl, track, rtpPort, rtcpPort)
 			if err != nil {
 				// retry if it's a bind error
 				if nerr, ok := err.(*net.OpError); ok {
@@ -239,7 +240,7 @@ func (s *source) runUdp(terminate chan struct{}, conn *gortsplib.ConnClient) boo
 		})
 	}
 
-	_, err := conn.Play(s.pconf.sourceUrl)
+	_, err := conn.Play(s.confp.sourceUrl)
 	if err != nil {
 		s.log("ERR: %s", err)
 		return true
@@ -289,7 +290,7 @@ func (s *source) runUdp(terminate chan struct{}, conn *gortsplib.ConnClient) boo
 
 	tcpConnDone := make(chan error)
 	go func() {
-		tcpConnDone <- conn.LoopUDP(s.pconf.sourceUrl)
+		tcpConnDone <- conn.LoopUDP(s.confp.sourceUrl)
 	}()
 
 	var ret bool
@@ -323,14 +324,14 @@ outer:
 
 func (s *source) runTcp(terminate chan struct{}, conn *gortsplib.ConnClient) bool {
 	for _, track := range s.tracks {
-		_, err := conn.SetupTcp(s.pconf.sourceUrl, track)
+		_, err := conn.SetupTcp(s.confp.sourceUrl, track)
 		if err != nil {
 			s.log("ERR: %s", err)
 			return true
 		}
 	}
 
-	_, err := conn.Play(s.pconf.sourceUrl)
+	_, err := conn.Play(s.confp.sourceUrl)
 	if err != nil {
 		s.log("ERR: %s", err)
 		return true
diff --git a/utils.go b/utils.go
index f9895f40..75f6fcad 100644
--- a/utils.go
+++ b/utils.go
@@ -74,6 +74,7 @@ func (db *doubleBuffer) swap() []byte {
 	return ret
 }
 
+// generate a sdp from scratch
 func sdpForServer(tracks []*gortsplib.Track) (*sdp.SessionDescription, []byte) {
 	sout := &sdp.SessionDescription{
 		SessionName: func() *sdp.SessionName {