Reset WHEP state when WHIP publisher changes

New publisher might not have Simulcast layers/need new keyframe

Author: Sean-Der

internal/webrtc/sessions/session/session.go

@@ -84,6 +84,7 @@ func (s *Session) AddHost(peerConnection *webrtc.PeerConnection) (err error) {
 		host.RemoveTracks()
 		return fmt.Errorf("session already has a host")
 	}
+	s.resetWHEPSessionsForNewHost()
 	host.WHEPSessionsSnapshot.Store(make(map[string]*whep.WHEPSession))
 	s.updateHostWHEPSessionsSnapshot()
 	s.HasHost.Store(true)
@@ -237,6 +238,18 @@ func (s *Session) updateHostWHEPSessionsSnapshot() {
 	host.WHEPSessionsSnapshot.Store(snapshot)
 }
 
+func (s *Session) resetWHEPSessionsForNewHost() {
+	s.WHEPSessionsLock.RLock()
+	for _, whepSession := range s.WHEPSessions {
+		if whepSession == nil {
+			continue
+		}
+
+		whepSession.ResetForNewPublisher()
+	}
+	s.WHEPSessionsLock.RUnlock()
+}
+
 // Get the status of the current session
 func (s *Session) GetStreamStatus() (status whipSessionStatus) {
 	s.WHEPSessionsLock.RLock()

internal/webrtc/sessions/whep/whep.go

@@ -137,6 +137,18 @@ func (w *WHEPSession) SendPLI() {
 	w.pliSender()
 }
 
+// Reset per-publisher delivery state when a new WHIP publisher connects.
+func (w *WHEPSession) ResetForNewPublisher() {
+	w.VideoLock.Lock()
+	defer w.VideoLock.Unlock()
+
+	w.AudioLayerCurrent.Store("")
+	w.VideoLayerCurrent.Store("")
+	w.videoLayerPriority = 0
+	w.videoLayerExplicit = false
+	w.IsWaitingForKeyframe.Store(true)
+}
+
 func (w *WHEPSession) updateVideoBitrateLocked(now time.Time) {
 	if w.videoBitrateWindowStart.IsZero() {
 		w.videoBitrateWindowStart = now