If it is a commercial type DVD format DVD Decrypter works pretty well.
http://www.videohelp.com/tools?tool=DVD_Decrypter
It sounds like it might be a DVD from a camcorder. If so, what type camcorder and recording mode were used? Maybe a few more details would help.
If the video is meant to be captured through the Firewire PC port I have had good luck with ScenalyzerLive.
http://www.scenalyzer.com/main.html
Of course both of these run on a Windows system.
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Rob Channell
One Way Motorsports
1979 911SC mostly stock
1972 911T Targa now with a good 2.7
1990 Miata (cheap 'n easy)
1993 C1500 Silverado (parts getter)