Well, it seems to be your lucky day then I did some searching and I suggest the following:
1. add the camera using the tab Custom Source,
2. set stream type to rtsp_tcp
3. in Address use one of the following URL´s
rtsp://username:password@IPnumber:88/videoMain This should give you 720p and max fps
rtsp://username:password@IPnumber:88/videoSub This gives you VGA..
I would very much like you to test the following. Maybe the camera support the ONVIF standard. Can you test to add the camera using the tab for ONVIF source. Search for the camera and if it find it enter username/password and continue. If it doesn´t find the camera it do not support ONVIF. I am just interested to know for future references.
Please report back how it goes,