I have a freeswitch system that (for the most part) works flawlessly for me.  However, I need to have an additional rtpmap line in the SDP when a call is answered.

My client sends the following SDP upon answering the call :

   m=audio 17214 RTP/AVP 0 19 101 100

   c=IN IP4 192.168.98.79

   a=rtpmap:0 PCMU/8000

   a=rtpmap:19 CN/8000

   a=rtpmap:101 telephone-event/8000

   a=fmtp:101 0-16

   a=rtpmap:100 X-NSE/8000

   a=fmtp:100 192-194

Freeswitch forwards the following SDP to the external gateway :

   m=audio 20654 RTP/AVP 0 19 101

   c=IN IP4 66.223.187.208

   a=rtpmap:0 PCMU/8000

   a=rtpmap:19 CN/8000

   a=rtpmap:101 telephone-event/8000

   a=fmtp:101 0-16

The other information appears fine.  Everything works, but my client-side is not receiving the a=rtpmap:100 line.

This issue appears regardless of whether or not I’m in proxy mode, bypass mode, or neither.

Using "sip_append_audio_sdp” has no effect on the answering SDP, only the initial offer.

Any ideas?

Thanks in advance,