Is there a specific configuration needed in sip.conf or pjsip.conf (or elsewhere in config files) to allow endpoints to upgrade an established audio only call to a call with audio and video? If a video call is started immediately when offered in an initial INVITE, everything works fine with two way video. However, my attempts to upgrade an established call from audio only to audio/video in a re-INVITE have experienced the following issues:
When I try to do this with Asterisk 11.24.1 using chan_sip, Asterisk responds to the new INVITE with a 200OK including SDP with only this line as regards video
m=video 0 RTP/AVP 127 126
This effectively rejects the attempt to upgrade to a video call. The INVITE is not passed on to the remote endpoint. I've tried with video_support=yes and video_support=always, to the same effect.
I also thought I'd try giving it a go with Asterisk 14.4.0 using pjsip as well. The behaviour with pjsip is different from chan_sip but still not right. Asterisk does respond to the upgrade to video INVITE with a 200OK including appropriate SDP for a video call, but it also doesn't pass on said INVITE to the remote endpoint, so the other endpoint never gets notified that an upgrade to video has been requested (notifying user to take action). If the other endpoint also upgrades to video and sends an INVITE to Asterisk as well, the video component of the call will then function, but this isn't ideal.
Am I missing some configuration items to get this working, or is this a problem with the SIP implementations for making an upgrade to audio/video from audio only in Asterisk?