I was going crazy

trying to watch C-Span video (Real Media via RTSP [real time streaming protocol]) - finally took look at my router log and it was logging blocks by ALG of RTSP protocol.
Went to Firewall Settings page in advanced and noticed that RTSP was checked in the ALG configuration section. The way I read the (mostly unhelpful) Help, this being checked should enable the router to deal with RTSP.
Well, I unchecked it, and now can watch video! So either I'm an idiot that can't understand the English help file, or the help file is exactly backwards, or the product with respect to RTSP is not working correctly.....