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Torchizard

Corrupted Copy

6 posts in this topic

I've been creating backups of all my CDs and DVDs in case they end up with scratches in the near future. I came across this one DVD with a documentary in the usual DVD (VIDEO_TS) format. The weird thing is that whenever I play it with WMP, it plays fine but whenever I try to copy it onto my HDD, it ends up all corrupted (still playable but with glitchy video and sound). This is the first time I've ever come across something like this. Any ideas why it's doing this?

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Physical scratches I would think. They are smoothed over by on-the-fly error correction during playback, but a good ripper will be far more stringent and even though it retries it will fail by design so that data is not corrupted..

I have been doing the same thing, digitizing opticals onto HDDs. I keep a low-power microscope handy and have learned to spot the scratches and dings that my ripper chokes on ( and note it is the same sectors on a bad disc even when trying in a different drive ).

I can often fix bad discs by polishing the defects, and only the defects ( and forget spinning cleaners that clean the whole thing). I try alcohol first, and then a thin clear plastic polish second. Note: wiping is NOT done in circular motion, but straight from edge to center or vice versa. The sectors are on a circular track much like a vinyl album so you want to NOT wipe "with the grain". What is actually happening by polishing is that the plastic layer which has a ding or scratch ( a recess ) is "lowered" slightly to match the recess, and the recess itself is partly filled to "raise" it slightly to match the normal surface. This operation decreases the shadow the sharp angles of a scratch produce, reducing the loss of reflected light back to the lens. More polishing means more equalization between the height of the normal plastic and the depth of the hole. Note that none of this has anything to do with the dye layer well below the plastic covering. If a scratch goes that deep you cannot polish it out. If it was critical data to be recovered you would have to look into a polymer liquid to fill it to reduce the shadow.

Of course we're talking about visible scratches. I have never yet found a bad optical disc, pressed or burned, that I couldn't locate the hole under a microscope. In my case, if there are no visible scratches or holes, then there are no problems. But there can be other things that cause random errors NOT in the same sector each time you try to rip it. Canned air to blow out the disc drive is very helpful, especially if you are popping discs in and out for days on end. I've done over a thousand audio and hundreds of data CDROMs. Cleaning hair and dust off the disc before inserting it is also critical. Canned air every so often on the drive.

Lastly, I have a lot of computers setup side by side when I do this so I can get an assembly line going. Trying the disc on different drives is a good debug step because there are differences between them. This will pinpoint whether it is a physical defect ( shows in same sector number across different computers ) or a random dust/hair incident.

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Just for the record:

http://www.msfn.org/board/topic/56005-repair-scratched-cd/

But, no, the symptoms are the "wrong" one for a physical defect.

It sounds much more like any of the possible anti-copy/anti-rip protections.

A very suitable way to identify a problematic area is usually DVDisaster:

http://dvdisaster.net/en/index.html

Yeah... It seems that it did have protection (Kinda weird that it has protection since it's just a two dollar DVD that was distributed with a newspaper a few years ago)

Also to avoid creating a new topic, i'm going to ask another question here... Do you know of any good tools that can scan a CD\DVD and create a list of files that are defective? I currently use IsoBuster for that but the enormous slowdown\non-responsiveness when it encounters bad sectors is unbearable.

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CDCheck is an old software but it still does it, is freeware for "non profit use" and is portable.

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Also to avoid creating a new topic, i'm going to ask another question here... Do you know of any good tools that can scan a CD\DVD and create a list of files that are defective? I currently use IsoBuster for that but the enormous slowdown\non-responsiveness when it encounters bad sectors is unbearable.

You were already pointed to DVDisaster which, as a "side effect" of it's intended usage does have nice "source verifying" capabilities.

jaclaz

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