In case others run into this and still are trying to get VLC to work, one other thing that IS working is the use of gstreamer on ubuntu. It has no problem grabbing the rtsp stream.
gst-launch-1.0 rtspsrc location=rtsp:/<username>:<pwd>@10.0.0.193:88/videoMain ! decodebin ...
One more bit of news on this... still stumped, but somehow using VLC on a Mac, was able to solve half of the problem. Using "rtsp:/<username>:<pw>@<my-ip>:88/videoMain", I am able to have VLC give me the audio from the camera. That shows that at least the ports and connections are working...
I just bought a Foscam R4S, and I cannot connect to it via RTSP. I am able to configure it from both the ios app and the web browser interface. I have tried every combination of rtsp url that I can find or dream up (with or without username/password, using port 554 or 88, using "/videoMain"...