you'll probably have to do it in a couple of steps. First, you'll have to rip the dvd to an avi or some other video format. Then, you'll have to extract the frames.
If I were going to do it, I would start with
vStrip[
^]. It's a command-line DVD ripping program, so you can interact with it programmatically. Then, I would look at this article:
Extract Frames from Video Files[
^]
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