Hi Benny, Thanks for your reply. I have seen the stream.c module and seen a function create_dtmf_payload().How the audio data from the sound device is related to dtmf. But i was not clear how the audio data from the microphone is packtized? the input for RTP packetization is pjmedia_frames continously read from jitterbuffer?am i right in my understanding? Please correct me if iam wrong? Thanks & Regards Rajeswari 5, 50, 500, 5000 - Store N number of mails in your inbox. Go to http://help.yahoo.com/l/in/yahoo/mail/yahoomail/tools/tools-08.html -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.pjsip.org/pipermail/pjsip_lists.pjsip.org/attachments/20080108/56aa1aa2/attachment.html