[asterisk-dev] storing INVITE fmtp and use it to send relay

[Alexander Traud]

> If I receive an INVITE with fmtp from a peer, it won't be used to build the
> INVITE to the egress right?

With Asterisk 13/chan_sip, it is possible to copy over the fmtp - even 1:1 -
I do this here with AMR-WB. I created a res/res_format_attr_ and adopted
format_parse_sdp_fmtp/format_generate_sdp_fmtp, just like the Opus sample.
Thanks to Asterisk 13, the selected codec of the ingress gets the first
priority for the egress.

> Is there any function [to] act like a proxy?

Mhm. I was not able to do that because here, Asterisk removed unknown codecs
and adds its allowed ones after the one selected for the ingress. So the
lines m=, a/v/t=, and their order are going to be different. But as stated,
copying over (one!) fmtp per format is possible. By the way, which
codec/format are you about?