matrix synapse javascript voip issue with voice

i'm trying to create a video call using matrix synapse and help of matrix-js-sdk library, I can make video call it working just fine but the issue is with voice transfering , the user who makes the call doesn't recieve any voice , video is working fine . my code to call

 call = sdk.createNewMatrixCall(
      client, room_id
    );   
    var remoteVideo = document.querySelector('#remote')
    call.placeVideoCall(
        remoteVideo,localVideo
    );

and answering code

client.on("Call.incoming", function(c) {
    console.log("Call ringing");
    document.getElementById("result").innerHTML = "<p>Incoming call...</p>";
    console.log(c ,'-------------------------')

    // this.setState({call:c})
    call = c
    _this.callListerner(call);    
    // call.answer()
});

   document.getElementById("answer").addEventListener('click',function()   {
      console.log("Answering call...");
      console.log("Call => %s", call);
      var localVideo = document.querySelector('#local')
      call.setLocalVideoElement(localVideo)
      var remoteVideo = document.querySelector('#remote')
      call.setRemoteVideoElement(remoteVideo)
      call.answer();
      console.log(call , 'sssssssssss')
      document.getElementById("result").innerHTML = "<p>Answered call.</p>";
  })

here is the code i'm testing = my code so far

sadly matrix doesn't have any good support , after digging in for days it turns out the issue is with firefox and this code works perfectly on chrome .