fix(TPC): Use addTrack instead of addStream in Unified-plan impl.

Do not try to configure encodings on the sender until they are available. This fixes an issue on Chrome (running in unified-plan mode) where unmuting the local source throws a 'Read-only field modified in setParameters()' error.

modules/RTC/TPCUtils.js

@@ -191,8 +191,7 @@ export class TPCUtils {
     /**
     * Adds {@link JitsiLocalTrack} to the WebRTC peerconnection for the first time.
     * @param {JitsiLocalTrack} track - track to be added to the peerconnection.
-    * @param {boolean} isInitiator - boolean that indicates if the endpoint is offerer
-    * in a p2p connection.
+    * @param {boolean} isInitiator - boolean that indicates if the endpoint is offerer in a p2p connection.
     * @returns {void}
     */
     addTrack(localTrack, isInitiator) {
@@ -238,13 +237,18 @@ export class TPCUtils {
         }
         logger.debug(`Adding ${localTrack} on ${this.pc}`);
 
-        // If the client starts with audio/video muted setting, the transceiver direction
-        // will be set to 'recvonly'. Use addStream here so that a MSID is generated for the stream.
+        // If the client starts with audio/video muted setting, the transceiver direction will be set to 'recvonly'.
         if (transceiver.direction === 'recvonly') {
             const stream = localTrack.getOriginalStream();
 
-            if (stream) {
-                this.pc.peerconnection.addStream(localTrack.getOriginalStream());
+            if (stream && track) {
+                try {
+                    this.pc.peerconnection.addTrack(track, stream);
+                } catch (error) {
+                    logger.error(`Adding ${localTrack} failed on ${this.pc}:${error?.message}`);
+
+                    return Promise.reject(error);
+                }
 
                 return this.setEncodings(localTrack).then(() => {
                     this.pc.localTracks.set(localTrack.rtcId, localTrack);
@@ -395,6 +399,12 @@ export class TPCUtils {
             .find(t => t.sender && t.sender.track && t.sender.track.kind === track.getType());
         const parameters = transceiver.sender.getParameters();
 
+        // Resolve if the encodings are not available yet. This happens immediately after the track is added to the
+        // peerconnection on chrome in unified-plan. It is ok to ignore and not report the error here since the
+        // action that triggers 'addTrack' (like unmute) will also configure the encodings and set bitrates after that.
+        if (!parameters?.encodings?.length) {
+            return Promise.resolve();
+        }
         parameters.encodings = this._getStreamEncodings(track);
 
         return transceiver.sender.setParameters(parameters);

modules/RTC/TraceablePeerConnection.js

@@ -1687,9 +1687,14 @@ TraceablePeerConnection.prototype.addTrack = function(track, isInitiator = false
 
     this.localTracks.set(rtcId, track);
 
-    // For p2p unified case, use addTransceiver API to add the tracks on the peerconnection.
-    if (browser.usesUnifiedPlan() && this.isP2P) {
-        this.tpcUtils.addTrack(track, isInitiator);
+    if (browser.usesUnifiedPlan()) {
+        try {
+            this.tpcUtils.addTrack(track, isInitiator);
+        } catch (error) {
+            logger.error(`Adding ${track} failed on ${this}: ${error?.message}`);
+
+            return Promise.reject(error);
+        }
     } else {
         // In all other cases, i.e., plan-b and unified plan bridge case, use addStream API to
         // add the track to the peerconnection.
@@ -1709,8 +1714,7 @@ TraceablePeerConnection.prototype.addTrack = function(track, isInitiator = false
         }
 
         // Muted video tracks do not have WebRTC stream
-        if (browser.usesPlanB() && browser.doesVideoMuteByStreamRemove()
-                && track.isVideoTrack() && track.isMuted()) {
+        if (browser.doesVideoMuteByStreamRemove() && track.isVideoTrack() && track.isMuted()) {
             const ssrcInfo = this.generateNewStreamSSRCInfo(track);
 
             this.sdpConsistency.setPrimarySsrc(ssrcInfo.ssrcs[0]);
@@ -1737,12 +1741,11 @@ TraceablePeerConnection.prototype.addTrack = function(track, isInitiator = false
             }
         }
     }
-
     let promiseChain = Promise.resolve();
 
     // On Firefox, the encodings have to be configured on the sender only after the transceiver is created.
     if (browser.isFirefox()) {
-        promiseChain = this.tpcUtils.setEncodings(track);
+        promiseChain = promiseChain.then(() => this.tpcUtils.setEncodings(track));
     }
 
     return promiseChain;