Computer: Algorithm
Scratch Catcher   (+6, -1)  [vote for, against]
Never fear an interrupted movie again.

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!

***

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.
-- redshift9, Dec 15 2002

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.
-- ry4an, Dec 15 2002


bash$ fsck /dev/dvd

i didnt know we needed a seperate program with a fancy name for this. baked.
-- ironfroggy, Dec 15 2002


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.

ironfroggy - I'm clueless. What the heck is bash$ fsck /dev/dvd ?
-- redshift9, Dec 15 2002


Unix command to run a check on a drive.
-- krelnik, Dec 16 2002


If you had lots of parallel (or even independent) read heads you cold probably beat the 8x barrier fairly easily.
-- st3f, Dec 16 2002


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?
-- supercat, Dec 16 2002


Fascinating. I usually use a bright light (such as the sun).

Of course, if there's an error in the encoding or something like that, my "Scratch Catcher" wouldn't work...
-- :-), Jun 25 2003


just copy the movie to the disk and look if there are errors.

also, fsck usually ist just a wrapper for different file systems' fsck tools.
-- erlehmann, Jan 08 2008


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.

-- Alvin, Apr 19 2016


When the played movie hit the part with the scratch it could just flash an advertisement for the correct amount of missing time.
-- bungston, Apr 19 2016



random, halfbakery