public Boolean isVideoOn(String participant) {
   VideoParticipant vp = _users.get(participant);
   if (vp == null) {
     LogSdk.w(TAG, "Participant " + participant + " not found!");
     return false;
   }
   Integer view_id = vp.getViewId();
   if (view_id != null && view_id != -1) {
     return _renders.get(view_id).isVideoOn();
   }
   return false;
 }
 private void fillEmptyRenders() {
   for (Map.Entry<String, VideoParticipant> e : _users.entrySet()) {
     VideoParticipant participant = e.getValue();
     if (participant.getViewId() == -1) {
       RenderViewData d = getFreeRender();
       if (d != null) {
         participant.setViewId(d._view_id);
         LogSdk.i(
             Utils.getOoVooTag(),
             "Add free render for " + participant._participantId + " as " + d._view_id);
         d._video_on = true;
         d._user = participant.getParticipantId();
         ConferenceCore.instance().receiveParticipantVideoOn(participant.getParticipantId());
       } else {
         break;
       }
     }
   }
 }