If a port is found for audio, the video port is taken as port+2. If that is unavailable, things break fast

https://github.com/SIPp/sipp/blob/v3.5.1/src/sipp.cpp#L2184..L2202
^-- tries 100 times

https://github.com/SIPp/sipp/blob/v3.5.1/src/sipp.cpp#L2213..L2230
^-- simply takes audio_port+2