Thanks for the response. My app wants to create sound in realtime depending on the user behavior. So if the queue contains allready too many bytes before the .write(newdata), it is not realtime, because this bytes will be played before. But if I use write too late, the queue is empty and it will be a gab. So the best idea for me would be, to get the current queue size. Is that possible or is there another way for me?