I've been playing with SDL for awhile, but have not had much luck with video surfaces. Only thing I've been able to accomplish is a seg fault.

I have a feeling that if you are trying to overlay or watermark video, your going to have an easier time using an off the shelf OSS solution.

Here's one that looks promising, it actually does use SDL and V4L. I'll have to check it out myself.

http://effectv.sourceforge.net/