I did a test that define pj_str_t sdp={ { sdp string}, len}; and call the pjmedia_sdp_parse to construct the SDP with the sdp str which defined staticlly. but it seems that the non standard sdp line has been deleted when the pjsip library processes the request.. Chenhui Xu At 2013-07-03 11:52:15,"Chenhui Xu" <xch0929 at 126.com> wrote: Hi, Recently, I was involved in a project which is based on PJSIP, and I encountered a issue that we have some non standard SDP lines, (please refer to the last bolder line) v=0 o=Chen 1372821751 1372821751 IN IP4 192.168.77.109 s=Chen c=IN IP4 192.168.77.109 t=0 0 m=video 5055 RTP/AVP 102 a=rtpmap:102 H264/90000 a=sendonly f=v/2/5/0/1/0a/// I did not find any API which manage to construct this line, so I created a sdp then call pjmedia_sdp_print() to print the SDP into a buffer, then I just strcat(buffer, "f=v/2/5/0/1/0a///\r\n") and call pjmedia_sdp_parse() to construct the new sdp. But it seems does not work. Any one can give some comments? Thanks, Chenhui Xu -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.pjsip.org/pipermail/pjsip_lists.pjsip.org/attachments/20130703/dbae161e/attachment-0001.html>