has anyone implement jitter buffer with APS?

APS has it's own buffer of frame to transmition but I can't quary how many frame there are left in the APS internal buffer..

what I have done, is to manege my own buffer before playing and sending one frame to play, every time I got a frame from the recorder (which is effectivly my timer for sending frame)

however, on some phone, I get all the time buffer underflow from the APS?

can I work with the buffer underflow?