fix(TPC) Stop munging remote desc for imploding the SIM groups.

Jicofo by default now strips the simulcast SSRCs and sends only the primary SSRC and RTX to all the receiving endpoints in the call. Therefore remote SDP munging is not required on the clients anymore.

modules/RTC/TraceablePeerConnection.js

@@ -2454,10 +2454,6 @@ TraceablePeerConnection.prototype.setRemoteDescription = function(description) {
             }
         }
         if (this.isSimulcastOn()) {
-            // Implode the simulcast ssrcs so that the remote sdp has only the first ssrc in the SIM group.
-            remoteDescription = this.simulcast.mungeRemoteDescription(remoteDescription);
-            this.trace('setRemoteDescription::postTransform (simulcast)', dumpSDP(remoteDescription));
-
             remoteDescription = this.tpcUtils.insertUnifiedPlanSimulcastReceive(remoteDescription);
             this.trace('setRemoteDescription::postTransform (sim receive)', dumpSDP(remoteDescription));
         }

modules/sdp/SDPSimulcast.spec.js

@@ -119,39 +119,4 @@ describe('sdp-simulcast', () => {
             });
         });
     });
-
-    describe('mungeRemoteDescription', () => {
-        it('should implode remote simulcast SSRCs into one FID group', () => {
-            const sdp = SampleSdpStrings.simulcastRtxSdp;
-            const desc = {
-                type: 'offer',
-                sdp: transform.write(sdp)
-            };
-            const newDesc = simulcast.mungeRemoteDescription(desc);
-            const newSdp = transform.parse(newDesc.sdp);
-            const fidGroups = getVideoGroups(newSdp, 'FID');
-            const simGroups = getVideoGroups(newSdp, 'SIM');
-
-            expect(fidGroups.length).toEqual(1);
-            expect(simGroups.length).toEqual(0);
-            expect(fidGroups[0].ssrcs).toContain('1757014965');
-            expect(fidGroups[0].ssrcs).toContain('984899560');
-        });
-
-        it('should implode remote simulcast SSRCs without RTX into one primary SSRC', () => {
-            const sdp = SampleSdpStrings.simulcastNoRtxSdp;
-            const desc = {
-                type: 'offer',
-                sdp: transform.write(sdp)
-            };
-            const newDesc = simulcast.mungeRemoteDescription(desc);
-            const newSdp = transform.parse(newDesc.sdp);
-            const fidGroups = getVideoGroups(newSdp, 'FID');
-            const simGroups = getVideoGroups(newSdp, 'SIM');
-
-            expect(fidGroups.length).toEqual(0);
-            expect(simGroups.length).toEqual(0);
-            expect(numVideoSsrcs(newSdp)).toEqual(1);
-        });
-    });
 });

modules/sdp/SdpSimulcast.ts

@@ -241,77 +241,4 @@ export default class SdpSimulcast {
             sdp: transform.write(session)
         });
     }
-
-    /**
-     * Munges the given media description by removing the SSRCs and related FID groups for the higher layer streams.
-     *
-     * @param description
-     * @returns
-     */
-    mungeRemoteDescription(description: Description) : Description {
-        if (!description || !description.sdp) {
-            return description;
-        }
-
-        const session = transform.parse(description.sdp);
-
-        for (const media of session.media) {
-            if (media.type !== MediaType.VIDEO) {
-                continue;
-            }
-
-            if (media.direction !== MediaDirection.SENDONLY) {
-                continue;
-            }
-
-            // Ignore m-lines that do not have any SSRCs or SSRC groups. These are the ones associated with remote
-            // sources that have left the call. These will be recycled when a new remote source joins the call.
-            if (!media.ssrcGroups?.length || !media?.ssrcs.length) {
-                continue;
-            }
-
-            // Cache the SSRCs and the source groups.
-            const mungedSsrcs = new Set(media.ssrcs.slice());
-            const mungedSsrcGroups = new Set(media.ssrcGroups.slice());
-            const fidGroups = media.ssrcGroups.filter(group => group.semantics === 'FID');
-            const simGroup = media.ssrcGroups.find(group => group.semantics === 'SIM');
-            const primarySsrc = simGroup?.ssrcs.split(' ')[0];;
-
-            // When simulcast and RTX are both enabled.
-            if (fidGroups.length && simGroup) {
-                const fidGroup = fidGroups.find(group => group.ssrcs.includes(primarySsrc));
-                const secondarySsrc = fidGroup.ssrcs.split(' ')[1];
-
-                for (const ssrcGroup of media.ssrcGroups) {
-                    if (ssrcGroup !== fidGroup) {
-                        mungedSsrcGroups.delete(ssrcGroup);
-                    }
-                }
-                for (const ssrc of media.ssrcs) {
-                    if (ssrc.id.toString() !== primarySsrc
-                        && ssrc.id.toString() !== secondarySsrc) {
-                        mungedSsrcs.delete(ssrc);
-                    }
-                }
-
-            // When simulcast is enabled but RTX is disabled.
-            } else if (simGroup) {
-                mungedSsrcGroups.delete(simGroup);
-
-                for (const ssrc of media.ssrcs) {
-                    if (ssrc.id.toString() !== primarySsrc) {
-                        mungedSsrcs.delete(ssrc);
-                    }
-                }
-            }
-
-            media.ssrcs = Array.from(mungedSsrcs);
-            media.ssrcGroups = Array.from(mungedSsrcGroups);
-        }
-
-        return new RTCSessionDescription ({
-            type: description.type,
-            sdp: transform.write(session)
-        });
-    }
 }

types/auto/modules/sdp/SdpSimulcast.d.ts

@@ -71,12 +71,5 @@ export default class SdpSimulcast {
      * @returns
      */
     mungeLocalDescription(description: Description): Description;
-    /**
-     * Munges the given media description by removing the SSRCs and related FID groups for the higher layer streams.
-     *
-     * @param description
-     * @returns
-     */
-    mungeRemoteDescription(description: Description): Description;
 }
 export {};