I've gotten over $200 in cash back from them at places I would have shopped anyway! Ebay, Staples, more! I put it at the top because they ROCK. Basically, you get a kickback from Ebates when buy.com or whoever pays them. Win-win. If you like throwing money away, don't use them!

Tuesday, October 14, 2008

CD (Compact Disc) Repair: Scratched and got holes? No problem!

I bought a bunch of CD's at a garage sale for on the order of 25 cents each. Mind you, this is good stuff. I mean, like 80's and 90's old guy stuff; examples: Dire Straits' "Brothers in Arms", Tom Petty and the Heartbreakers' "Damn the Torpedoes", and many from artists like ZZ Top, Bob Seger, Stevie Ray Vaughan, and more. So you're jealous of my deal, BUT...

When I got them home and started examining them, a lot were scratched on the plastic layer like they had been used for Frisbees.

That's not a big deal, as you can polish that out.

Worse, in may cases, the oxide layer where the information lives had pinholes and big gouges in it. So the information that was there is GONE.

NOT TO WORRY! I found this blurb-

"The digital encoding for error detection and correction is called the Cross Interleave Reed-Solomon Code or CIRC. To describe this as simply as possible, the CIRC code consists of two parts: interleaving of data so that a dropout or damage will be spread over enough physical area (hopefully) to be reconstructed and a CRC (Cyclic Redundancy Check) like error correcting code. Taken together, these two techniques are capable of some remarkable error correction. The assumption here is that most errors will occur in bursts as a result of dust specs, scratches, imperfections such as pinholes in the aluminum coating, etc. For example, the codes are powerful enough to totally recover a burst error of greater than 4,000 consecutive bits - about 2.5 mm on the disc. With full error correction implemented (this is not always the case with every CD player), it is possible to put a piece of 2 mm tape radially on the disc or drill a 2 mm hole in the disc and have no audio degradation. Some test CDs have just this type of defect introduced deliberately. "

So, a pinhole is not a problem! I also found out that the information starts in the middle of the CD by the hole.

(Ok techies, I know it error correction isn't this simple in total, and some info might be missing, but as long as I can't hear the miss, then big deal. I rip my CD's to 160kbit too, they sound fine to me!)

So, depending on where your damage is, and how big, that CD may be fine to play.

Better yet, you can still rips some tracks as an MP3 (if not all were readable) and reburn it, or as I did, just use a CD copying program to copy it.

You would want to do this if you have a CD that skips due to scratches, because the computer can read it slowly, correct the errors, and then burn you a nice unscratched legal copy.

Note: If you are using Toast 9 (and perhaps other versions) I would deselect the option to 'Use Disc Recovery' when you make your copy as that will not truly recover all your data. I'm not sure what it would do to an audio disc, but with a file, your data will not be there if the scratch is too big.

In my case, CDs copied and verified just fine, pinholes and all. It's perfectly legal, as you own the CD.

I'm even keeping my copy of ZZ Top's "Greatest Hits" that suffered what looks like shotgun damage because I own another original copy, and I can gift or sell that one with a copy, probably that's legal too as I own two original CD's.

Happy CD Recovery!

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