update media session to callee (#78)

lib/call-session.js

@@ -107,6 +107,11 @@ class CallSession extends Emitter {
     return this._mediaReleased;
   }
 
+  get calleeIsUsingSrtp() {
+    const tp = this.rtpEngineOpts?.uac?.mediaOpts['transport-protocol'];
+    return tp && -1 !== tp.indexOf('SAVP');
+  }
+
   subscribeForDTMF(dlg) {
     if (!this._subscribedForDTMF) {
       this._subscribedForDTMF = true;
@@ -627,7 +632,7 @@ Duration=${payload.duration} `
 
       /* if this is a re-invite from the FS to change media anchoring, avoid sending the reinvite out */
       let sdp;
-      if (isReleasingMedia) {
+      if (isReleasingMedia && !this.calleeIsUsingSrtp) {
         this.logger.info(`got a reinvite from FS to ${reason}`);
         sdp = dlg.other.remote.sdp;
         if (!answerMedia.flags.includes('port latching')) answerMedia.flags.push('port latching');