[SR-Users] rtpproxy not forwarding rtp packets.

Greetings list, I have kamailio server behind nat with rptproxy. But i am getting no voice on the call. After taking trace i could see that rtpproxy was getting rtp packets but not packets was being forwarded towards callee side. Though i see in rtpproxy logs, packets being relayed from caller side. Does rtpproxy wait to receive a single rtp frame from callee before fowarding that to callee? Since, i am getting no rtp from callee. So, might be rptrpoxy is waiting to learn source address of callee side rtp, that is why it is not forwarding rtp packets from caller towards callee. Any pointer/suggestion is much appreciated. Best Regards, Aqs Younas