In my Asterisk 13, I setup extensions so users are able to dial/test each offered/supported audio codec. 501 is ulaw, 502 is alaw, and so on. In chan_sip, I used SIP_CODEC_INBOUND to achieve this. That was discussed before in the year 2014. In March 2017, this was discussed again. However yet, I was not able to find the mentioned thread. Ideally, I would like to reject the call, when the offer does not match the audio codec of the called extension. However, getting the same as of chan_sip would be a start.
Is that possible with PJSIP now. Was this added with Asterisk 14/15? Otherwise I have to report it as missing feature…