I've just had a problem with a set of commercial video dvds. On one disk of the set, there was a problem with a VOB file. The dvd looks perfect and would play on my cheapo standalone dvd player but would not play on any of my 4 pc dvd drives. Apparently a marginal read problem.

I attempted to decrypt/copy the files to make a playable copy. I tried Dvd Decrypter, Isobuster, Dead Disk Doctor, CD/DVD Data Recovery without luck. The first two just hung up at the fault. Dead Disk Doctor said the disk was unreadable (duhhh) and went no further. CD/DVD Data Recovery took forever to produce an unplayable file. For no particular reason other than desperation I tried SmartRipper, which needed the dvd to be played in a player to unlock the files. It copied the defective file almost without blinking, finishing with only 2 defective blocks.

Having got that to work I went back to DVD Decrypter. I opened the dvd first in PowerDvd (and paused) and then tried to decrypt the problem file. It decrypted without a single read error.

I'm not making any comment on the capabilities of any of the above software. In my case trying different software and unlocking with a player did the job.