Label tracks explicitly.

For now, this is only used to request screen sharing as opposed to normal
videos.  In the future, it will be used for simulcasting.

client.go

@@ -26,7 +26,6 @@ import (
 	"github.com/gorilla/websocket"
 	"github.com/pion/rtcp"
 	"github.com/pion/rtp"
-	"github.com/pion/sdp"
 	"github.com/pion/webrtc/v2"
 )
 
@@ -104,6 +103,7 @@ type clientMessage struct {
 	Offer       *webrtc.SessionDescription `json:"offer,omitempty"`
 	Answer      *webrtc.SessionDescription `json:"answer,omitempty"`
 	Candidate   *webrtc.ICECandidateInit   `json:"candidate,omitempty"`
+	Labels      map[string]string          `json:"labels,omitempty"`
 	Del         bool                       `json:"del,omitempty"`
 	Request     []string                   `json:"request,omitempty"`
 }
@@ -301,13 +301,14 @@ func addUpConn(c *client, id string) (*upConnection, error) {
 		}
 		track := &upTrack{
 			track:      remote,
+			label:      u.labels[remote.ID()],
 			cache:      packetcache.New(96),
 			rate:       estimator.New(time.Second),
 			jitter:     jitter.New(remote.Codec().ClockRate),
 			maxBitrate: ^uint64(0),
 		}
 		u.tracks = append(u.tracks, track)
-		done := len(u.tracks) >= u.trackCount
+		done := u.complete()
 		if remote.Kind() == webrtc.RTPCodecTypeVideo {
 			atomic.AddUint32(&c.group.videoCount, 1)
 		}
@@ -830,28 +831,27 @@ func sendRecovery(p *rtcp.TransportLayerNack, track *downTrack) {
 	}
 }
 
-func countMediaStreams(data string) (int, error) {
-	desc := sdp.NewJSEPSessionDescription(false)
-	err := desc.Unmarshal(data)
+func negotiate(c *client, id string, down *downConnection) error {
+	offer, err := down.pc.CreateOffer(nil)
 	if err != nil {
-		return 0, err
+		return err
 	}
-	return len(desc.MediaDescriptions), nil
-}
 
-func negotiate(c *client, id string, pc *webrtc.PeerConnection) error {
-	offer, err := pc.CreateOffer(nil)
+	err = down.pc.SetLocalDescription(offer)
 	if err != nil {
 		return err
 	}
-	err = pc.SetLocalDescription(offer)
-	if err != nil {
-		return err
+
+	labels := make(map[string]string)
+	for _, t := range down.tracks {
+		labels[t.track.ID()] = t.remote.label
 	}
+
 	return c.write(clientMessage{
-		Type:  "offer",
-		Id:    id,
-		Offer: &offer,
+		Type:   "offer",
+		Id:     id,
+		Offer:  &offer,
+		Labels: labels,
 	})
 }
 
@@ -867,7 +867,7 @@ func sendICE(c *client, id string, candidate *webrtc.ICECandidate) error {
 	})
 }
 
-func gotOffer(c *client, offer webrtc.SessionDescription, id string) error {
+func gotOffer(c *client, id string, offer webrtc.SessionDescription, labels map[string]string) error {
 	var err error
 	up, ok := c.up[id]
 	if !ok {
@@ -879,12 +879,6 @@ func gotOffer(c *client, offer webrtc.SessionDescription, id string) error {
 	if c.username != "" {
 		up.label = c.username
 	}
-	n, err := countMediaStreams(offer.SDP)
-	if err != nil {
-		log.Printf("Couldn't parse SDP: %v", err)
-		n = 2
-	}
-	up.trackCount = n
 	err = up.pc.SetRemoteDescription(offer)
 	if err != nil {
 		return err
@@ -900,6 +894,8 @@ func gotOffer(c *client, offer webrtc.SessionDescription, id string) error {
 		return err
 	}
 
+	up.labels = labels
+
 	return c.write(clientMessage{
 		Type:   "answer",
 		Id:     id,
@@ -907,7 +903,7 @@ func gotOffer(c *client, offer webrtc.SessionDescription, id string) error {
 	})
 }
 
-func gotAnswer(c *client, answer webrtc.SessionDescription, id string) error {
+func gotAnswer(c *client, id string, answer webrtc.SessionDescription) error {
 	conn := getDownConn(c, id)
 	if conn == nil {
 		return protocolError("unknown id in answer")
@@ -934,11 +930,7 @@ func gotICE(c *client, candidate *webrtc.ICECandidateInit, id string) error {
 	return pc.AddICECandidate(*candidate)
 }
 
-func (c *client) setRequested(audio, video bool) error {
-	if audio == c.requestedAudio && video == c.requestedVideo {
-		return nil
-	}
-
+func (c *client) setRequested(requested []string) error {
 	if c.down != nil {
 		for id := range c.down {
 			c.write(clientMessage{
@@ -949,8 +941,7 @@ func (c *client) setRequested(audio, video bool) error {
 		}
 	}
 
-	c.requestedAudio = audio
-	c.requestedVideo = video
+	c.requested = requested
 
 	go func() {
 		clients := c.group.getClients(c)
@@ -962,15 +953,13 @@ func (c *client) setRequested(audio, video bool) error {
 	return nil
 }
 
-func (c *client) requested(kind webrtc.RTPCodecType) bool {
-	switch kind {
-	case webrtc.RTPCodecTypeAudio:
-		return c.requestedAudio
-	case webrtc.RTPCodecTypeVideo:
-		return c.requestedVideo
-	default:
-		return false
+func (c *client) isRequested(label string) bool {
+	for _, r := range c.requested {
+		if label == r {
+			return true
+		}
 	}
+	return false
 }
 
 func pushTracks(c *client, conn *upConnection, tracks []*upTrack, done bool, label string) {
@@ -989,7 +978,7 @@ func clientLoop(c *client, conn *websocket.Conn) error {
 	go clientReader(conn, read, c.done)
 
 	defer func() {
-		c.setRequested(false, false)
+		c.setRequested([]string{})
 		if c.up != nil {
 			for id := range c.up {
 				delUpConn(c, id)
@@ -1044,7 +1033,7 @@ func clientLoop(c *client, conn *websocket.Conn) error {
 			case addTrackAction:
 				var down *downConnection
 				var err error
-				if c.requested(a.track.track.Kind()) {
+				if c.isRequested(a.track.label) {
 					down, _, err = addDownTrack(
 						c, a.remote.id, a.track,
 						a.remote)
@@ -1055,7 +1044,7 @@ func clientLoop(c *client, conn *websocket.Conn) error {
 					down = getDownConn(c, a.remote.id)
 				}
 				if a.done && down != nil {
-					err = negotiate(c, a.remote.id, down.pc)
+					err = negotiate(c, a.remote.id, down)
 					if err != nil {
 						return err
 					}
@@ -1080,7 +1069,7 @@ func clientLoop(c *client, conn *websocket.Conn) error {
 					copy(tracks, u.tracks)
 					go pushTracks(
 						a.c, u, tracks,
-						len(tracks) >= u.trackCount-1,
+						u.complete(),
 						u.label,
 					)
 				}
@@ -1141,15 +1130,7 @@ func clientLoop(c *client, conn *websocket.Conn) error {
 func handleClientMessage(c *client, m clientMessage) error {
 	switch m.Type {
 	case "request":
-		var audio, video bool
-		for _, s := range m.Request {
-			switch(s) {
-			case "audio": audio = true
-			case "video": video = true
-			default: log.Printf("Unknown request %v", s)
-			}
-		}
-		err := c.setRequested(audio, video)
+		err := c.setRequested(m.Request)
 		if err != nil {
 			return err
 		}
@@ -1164,7 +1145,7 @@ func handleClientMessage(c *client, m clientMessage) error {
 		if m.Offer == nil {
 			return protocolError("null offer")
 		}
-		err := gotOffer(c, *m.Offer, m.Id)
+		err := gotOffer(c, m.Id, *m.Offer, m.Labels)
 		if err != nil {
 			return err
 		}
@@ -1172,7 +1153,7 @@ func handleClientMessage(c *client, m clientMessage) error {
 		if m.Answer == nil {
 			return protocolError("null answer")
 		}
-		err := gotAnswer(c, *m.Answer, m.Id)
+		err := gotAnswer(c, m.Id, *m.Answer)
 		if err != nil {
 			return err
 		}

group.go

@@ -26,6 +26,7 @@ import (
 
 type upTrack struct {
 	track                *webrtc.Track
+	label                string
 	rate                 *estimator.Estimator
 	cache                *packetcache.Cache
 	jitter               *jitter.Estimator
@@ -74,11 +75,27 @@ func (up *upTrack) hasRtcpFb(tpe, parameter string) bool {
 }
 
 type upConnection struct {
-	id         string
-	label      string
-	pc         *webrtc.PeerConnection
-	trackCount int
-	tracks     []*upTrack
+	id     string
+	label  string
+	pc     *webrtc.PeerConnection
+	tracks []*upTrack
+	labels map[string]string
+}
+
+func (up *upConnection) complete() bool {
+	for id, _ := range up.labels {
+		found := false
+		for _, t := range up.tracks {
+			if t.track.ID() == id {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return false
+		}
+	}
+	return true
 }
 
 type bitrate struct {
@@ -150,16 +167,15 @@ type downConnection struct {
 }
 
 type client struct {
-	group          *group
-	id             string
-	username       string
-	permissions    userPermission
-	requestedAudio bool
-	requestedVideo bool
-	done           chan struct{}
-	writeCh        chan interface{}
-	writerDone     chan struct{}
-	actionCh       chan interface{}
+	group       *group
+	id          string
+	username    string
+	permissions userPermission
+	requested   []string
+	done        chan struct{}
+	writeCh     chan interface{}
+	writerDone  chan struct{}
+	actionCh    chan interface{}
 
 	mu   sync.Mutex
 	down map[string]*downConnection

static/sfu.css

@@ -65,6 +65,11 @@ h1 {
     margin-right: 0.4em;
 }
 
+#requestselect {
+    width: 8em;
+    text-align-last: center;
+}
+
 #main {
     display: flex;
 }

static/sfu.html

@@ -47,8 +47,12 @@
         <label for="sharebox">Share screen:</label>
         <input id="sharebox" type="checkbox" disabled/>
 
-        <label for="requestbox">Receive video:</label>
-        <input id="requestbox" type="checkbox" checked>
+        <label for="requestselect">Receive:</label>
+        <select id="requestselect">
+          <option value="audio">audio only</option>
+          <option value="screenshare">screen share</option>
+          <option value="everything" selected>everything</option>
+        </select>
       </div>
     </div>
 

static/sfu.js

@@ -39,6 +39,7 @@ function Connection(id, pc) {
     this.label = null;
     this.pc = pc;
     this.stream = null;
+    this.labels = {};
     this.iceCandidates = [];
     this.timers = [];
     this.audioStats = {};
@@ -140,9 +141,9 @@ document.getElementById('sharebox').onchange = function(e) {
     setShareMedia(this.checked);
 };
 
-document.getElementById('requestbox').onchange = function(e) {
+document.getElementById('requestselect').onchange = function(e) {
     e.preventDefault();
-    sendRequest(this.checked);
+    sendRequest(this.value);
 };
 
 async function updateStats(conn, sender) {
@@ -312,6 +313,7 @@ async function setLocalMedia(setup) {
     let c = up[localMediaId];
     c.stream = stream;
     stream.getTracks().forEach(t => {
+        c.labels[t.id] = t.kind
         let sender = c.pc.addTrack(t, stream);
         c.setInterval(() => {
             updateStats(c, sender);
@@ -358,6 +360,7 @@ async function setShareMedia(setup) {
                 document.getElementById('sharebox').checked = false;
                 setShareMedia(false);
             };
+            c.labels[t.id] = 'screenshare';
             c.setInterval(() => {
                 updateStats(c, sender);
             }, 2000);
@@ -485,7 +488,7 @@ function serverConnect() {
                 username: up.username,
                 password: up.password,
             });
-            sendRequest(document.getElementById('requestbox').checked);
+            sendRequest(document.getElementById('requestselect').value);
             resolve();
         };
         socket.onclose = function(e) {
@@ -508,7 +511,7 @@ function serverConnect() {
             let m = JSON.parse(e.data);
             switch(m.type) {
             case 'offer':
-                gotOffer(m.id, m.offer);
+                gotOffer(m.id, m.labels, m.offer);
                 break;
             case 'answer':
                 gotAnswer(m.id, m.answer);
@@ -556,14 +559,30 @@ function serverConnect() {
     });
 }
 
-function sendRequest(video) {
+function sendRequest(value) {
+    let request = [];
+    switch(value) {
+    case 'audio':
+        request = ['audio'];
+        break;
+    case 'screenshare':
+        request = ['audio', 'screenshare'];
+        break;
+    case 'everything':
+        request = ['audio', 'screenshare', 'video'];
+        break;
+    default:
+        console.error(`Uknown value ${value} in sendRequest`);
+        break;
+    }
+
     send({
         type: 'request',
-        request: video ? ['audio', 'video'] : ['audio'],
+        request: request,
     });
 }
 
-async function gotOffer(id, offer) {
+async function gotOffer(id, labels, offer) {
     let c = down[id];
     if(!c) {
         let pc = new RTCPeerConnection({
@@ -587,6 +606,8 @@ async function gotOffer(id, offer) {
         };
     }
 
+    c.labels = labels;
+
     await c.pc.setRemoteDescription(offer);
     await addIceCandidates(c);
     let answer = await c.pc.createAnswer();
@@ -1007,6 +1028,7 @@ async function negotiate(id) {
     send({
         type: 'offer',
         id: id,
+        labels: c.labels,
         offer: offer,
     });
 }