h a l f b a k e r yThis is what happens when one confuses "random" with "profound."
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Have you ever rented a DVD from the video store, or bought one used, only to be rudely surprised by a crippling scratch one hour into the film that makes the disc unplayable?
Scratch Catcher is a simple application for use with any computer that has a DVD drive. Before watching a movie, let Scratch
Catcher give the disc a quick scan for errors. If the disc passes the test, you may enjoy your movie with confidence. If the disc has a nasty scratch, well, at least you didn't find out the hard way.
Scratch Catcher can also be used on compact discs, so you can check out a used CD you've just bought. If you own a video store or a music shop that deals in used discs, Scratch Catcher will help with the quality control of your inventory. If you're a customer with a laptop, you can check a disc even before buying it!
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A big part of Scratch Cather's usefulness depends on how fast it's possible to scan a disc. Frankly, I don't know what the technical limitations are for something like this. I'd say 8X would be the minimum acceptable speed - you'd have to be able to check a two hour film in no more than fifteen minutes.
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I wonder if perhaps scanning could be done by a portable device with the form factor of a sony discman, but not by attempting to read the contents of the disk but by either physically or optically just checking the surface for damage. I know I've fixed scratched disks with turtle wax before, and I think something w/ just a smooth surface and an array of pressure sensors could find a depression in a disk based only on "touch". Doing so would take only a second or so and be do-able before one leaves the video store. |
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i didnt know we needed a seperate program with a fancy name for this. baked. |
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ry4an - Not a bad suggestion, but what if you got a disc that someone had *unsuccessfully* tried to fix with Turtle Wax? There would be no scratch to detect, since the wax would have filled it in, but the disc would still be unplayable. |
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ironfroggy - I'm clueless. What the heck is bash$ fsck /dev/dvd ? |
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Unix command to run a check on a drive. |
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If you had lots of parallel (or even independent) read heads you cold probably beat the 8x barrier fairly easily. |
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ironfroggy -- Does fsck do a full surface check? I thought it only checked for the validity of the directory and inode structures. Of course, since I don't think dvd's have inodes, I'm not quite sure what it would do; does fsck adapt itself suitably to other file systems? |
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Fascinating. I usually use a bright light (such as the sun). |
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Of course, if there's an error in the encoding or something like that, my "Scratch Catcher" wouldn't work... |
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just copy the movie to the disk and look if there are errors. |
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also, fsck usually ist just a wrapper for different file systems' fsck tools. |
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Certainly most of the data on the disc is still intact. If
so, then there should be an online service to allow auto-
matic downloading of the corrupt portions.
They would probably want to require users to provide a
cryptographic hash of randomly selected parts of the disc
to make sure you actually have the disc and aren't just
trying to download the data a little at a time.
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When the played movie hit the part with the scratch it could just flash an advertisement for the correct amount of missing time. |
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