code: public RespokeCall startCall(RespokeCall.Listener callListener, Context context, GLSurfaceView glView, boolean audioOnly) {
          RespokeCall call = null;
  
          if ((null != signalingChannel) && (signalingChannel.connected)) {
              call = new RespokeCall(signalingChannel, this, false);
              call.setListener(callListener);
  
              call.startCall(context, glView, audioOnly);
          }
  
          return call;
      }
docs: Create a new call with audio and optionally video.
  
  @param callListener  A listener to receive notifications of call related events
  @param context       An application context with which to access system resources
  @param glView        A GLSurfaceView into which video from the call should be rendered, or null if the call is audio only
  @param audioOnly     Specify true for an audio-only call
  
  @return A new RespokeCall instance