How do I combine two identical damaged DVDs into one good one?

December 16, 2006 7:43 PM

I have two DVDs with identical content, both damaged in different places. How can I combine the "good" data from each DVD to make one perfect copy?

I burned two copies of a DVD of family footage, so that even if one disc had errors, we'd still have something to show the grandparents. However, both copies seem to have errors that prevent them from being copied correctly using a PC. So, for example, Nero says "Cannot copy this disk to a DVD", and DVD Decrypter craps out with sector errors (even if I select "Ignore").
However, it craps out at different places on each disk, so it seems like it should be possible to combine the data from the two disks to make one error-free "super-disk" that will rule us all, or at least play correctly. Google turns up nothing that seems relevant, although it may be a terminology problem.
So: How do I combine the data from two identical damaged DVDs into one good DVD?

posted by bakerybob to computers & internet (16 comments total)

If you're using a Windows machine, DVD Decrypter might be a good place to start, if you haven't tried it yet.

You could try to extract the VOB files from the DVD and, if they're in different segments, you *might* be able to manually combine the files from each disc. Just a guess, though, since my knowledge of DVD encoding and decryption is rather limited.
posted by dhammond at 7:54 PM on December 16, 2006

Can you see the files on the DVDs?
posted by nathancaswell at 7:54 PM on December 16, 2006

As dhammond pointed out, if you can see the files you could copy them into two different directories and use a program to open the VOB files. Maybe you'll be able to see the corruption and mix and match between the directories. I don't know a PC program that will open VOBs but I'm sure they're out there.
posted by nathancaswell at 7:56 PM on December 16, 2006

Adobe Premier Elements and Roxio Easy Media Creator can read VOB files.
posted by JayRwv at 8:02 PM on December 16, 2006

VirtualDub-MPEG2 is very useful for opening VOBs and AVIs, though you may have to install a codec. This should allow you to look at what's on each file.
posted by dhammond at 8:05 PM on December 16, 2006

Thanks for the great advice! Copying both to the hard drive and picking the file that copies correctly works in most cases - however, there are still a couple of files that can't be copied from either disk - both come up with a cyclic redundancy check error in Windows.
posted by bakerybob at 8:17 PM on December 16, 2006

I don't know the specific software to do it, but here's a concept for others to run with: If you rip images of both discs and then mount them both simultaneously using virtual-dvd software, could you then define a software raid-1 that would discard the bad-CRC sectors from either disc and return the good-CRC sectors when they're available?
posted by Myself at 8:27 PM on December 16, 2006

Oftentimes I find that DVDFab Decrypter (free) will successfully rip DVDs that cause DVD Shrink or DVD Decrypter to fail.
posted by forallmankind at 8:34 PM on December 16, 2006

Although I've never used it for this, ddrescue may work for you. It allows you to copy data from a hard drive (or CD/DVD I believe) and will skip over any damaged blocks it can't read, leaving holes in the copy. If you run it on multiple identical sources, it will fill in the holes if possible. This should result in a complete DVD image unless certain blocks are bad on both discs. I'm not sure if there is a windows port, but the tool is included on many Linux live CDs you could download and run.
posted by Amaterasu at 8:35 PM on December 16, 2006 [2 favorites]

Find a friend who uses Linux. Linux (and probably OSX) treat DVDs and HDs just like a simple file. Your new friend should be able to use the 'dd' program to read the raw data from the first DVD into a file until an error is reached, then read the data from the second DVD into a second file starting at the error point. Repeat until there are several good files containing all of the data, then concatenate them and burn to a new DVD.

For instance, say the first DVD has errors in blocks 100 and 500, and the second DVD has errors in blocks 200 and 600.

• dd if=/dev/dvd of=part1 count=199 # from DVD2
• dd if=/dev/dvd of=part2 skip=199 count=300 # from DVD1
• dd if=/dev/dvd of=part3 skip=499 count=1 # from DVD2
• dd if=/dev/dvd of=part4 skip=500 # from DVD1

You now have:

• part1 (1-199 from DVD2)
• part2 (200-499 from DVD1)
• part3 (500 from DVD2)
• part4 (501-end from DVD1)

And you can burn a new DVD with: 'cat part1 part2 part3 part4 | dd of=/dev/dvd'

On preview: ddrescue seems to be the automated version of this. :)
posted by zengargoyle at 8:50 PM on December 16, 2006

ddrescue does sound like exactly what I'm looking for, but unfortunately all of my friends are Windows users. Does a similar program exist for Windows?
I'm down to one file that can't be copied from either disk, even using DVDFab Decrypter.
posted by bakerybob at 9:30 PM on December 16, 2006

all of my friends are Windows users

you know, it's worth a shot asking them to try ripping the discs - you can quite often get different results reading from different drives.
posted by forallmankind at 10:04 PM on December 16, 2006

Easy!

Open DvdDecrypter's options. Disable the checkbox that says "lock CD/DVD tray during extraction." When the error box comes up, simply switch disks and hit "retry".
posted by archagon at 10:28 PM on December 16, 2006 [2 favorites]

(FYI, it's under "device.")
posted by archagon at 2:51 AM on December 17, 2006

Archagon: Perfect! The method you described was incredibly easy, and did the job without a single hitch. Thank you so much!
posted by bakerybob at 5:33 AM on December 17, 2006

Just be sure to play it through. I'm pretty sure the method works, but there's a very minor chance that I might be wrong.
posted by archagon at 6:03 AM on December 17, 2006