Series of still images from a movie

What is the easiest way to get a series of images from a movie?

I have seen much posted on getting 1 image at a time, but I need something that will take a movie and automatically grab images from every x seconds, where I can set x to be whatever I want it to be.

I have seen programs that do this but create almost a mosaic or montage - but I need individual images.

If I can watermark, all the better, but it's not a show-stopper.

Thanks in advance for recommendations.