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Testing CDs

Alexander Noé, Apr 04, 2005

C1, C2 and CU

When scanning CDs, you'll get numbers for C1, C2 and CU. A properly recorded CD does not show any C2 errors, and especially not any CU errors. If you are getting C2/CU errors on pressed audio cds, then either the disc is heavily damaged due to scratches or finger prints, or the CD in question is intentionally damaged by the music industry (they call it "CactusData Shield 200" and claim that it were a protection against copying).

A disc which has been intentionally damaged by the music industry can look like this: This is an 800 MB CD-R, recorded quite some time ago:
scan at 40x scan at 40x

If a recorded CD-R looks like this, you should make a backup and throw the old disc away.

Scan speed

Depending on the drive you are using and the exact type of the CD, you can perform scans at speeds up to 48x. However, some people claim that higher scan speeds lead to an inaccurate result.

This is simply wrong. The result you receive tells how much work the error correction had to do when reading the disc. That means, if the result is good even at higher speeds, the disc is good. If higher scan speeds lead to severely increasing error rates, the drive has trouble with the disc in question. The following 3 pictures show a Taiyo Yuden CD-R, recorded at 40x speed in an Asus DRW-1608P, scanned at 4x, 24x and 48x:

scan at 4x
scan at 24x
scan at 48x