How do I take screen shots on DVD movies and protected content?

This is deliberate from Apple and you will not be able to take screen shots using DVD player.

You can either use VLC and then a screen shot program (Cmd-3 and Cmd-4 works for me), or transcode your DVD to a QuickTime movie using Handbrake (which may take too long for you to find it interesting). The latter will allow you to use QuickTime player which can do quite a bit.

If you go to control & click 'use current frame as jacket picture'. Then click stop, your selected frame should come up - no matter where you stop the film from now on this still is what will show, that's what 'jacket picture' means.

Take a screenshot of the Jacket Picture & it should come up on your desktop like normal!

You should be able to capture screen shots by playing the movie in VLC and pressing alt+cmd+S. This is a more detailed guide for the windows version of VLC, but it should apply for the mac version as well!