Hi, I'm trying to add a watermark and a credits image to all of my old videos. I downloaded them off YouTube so they are all flv (H.264?). Is there some software that will allow me do simple edits in batches? I know a little bit of Python and tried looking at some of the library but they all seem like overkill (and way above my head). So is there a solution besides getting some software and going through all my videos and doing it manually?

They are all mostly the same length, but it would be nice to specify a relative position for my credits. e.g. show a static image for 10 seconds when the video is at 95%