I don't know if you've looked in the help section of Crestrons website yet but, if you search for "streaming" it should bring up some documents that show the best rtsp/mjpeg settings to use for specific brands/models. I'm not sure if hikvisiin is in there, but it would be worth a look for sure
IMO, though, you are better off using mjpeg with the Crestron app. I have 8 cams in my system and the 7 that don't support rtsp take about a second or two to start streaming. The one that uses rtsp used to take about 5-6 seconds to load but has been taking a good 12-15 seconds to load lately.
Steve McNally