Wow. Well, you know what happens when you "assume"...

Was this some kid's science project?

If, by some ill-designed method, CD-R copies were made by a mechanical method (duplicating the media representation rather than the recovered & regenerated signal), then there would be a good chance that bit drift would corrupt some data eventually.

However, when a CD-R is read, the drive's interface only sends a "1" or a "0" back to the host computer. It cannot possibly send an ambiguous value such as "0.54." The A/D converter(s) and CRC ensure that no single analog errors are passed to the next generation. Sure, the media is still analog, but that layer of digital regeneration makes it all work.

This actually reminds me of an argument I had at a consulting gig a couple years ago: a know-it-all engineer wrote a test plan that assumed (nay, expected!) the analog optical power level coming out of a SONET mux to reflect the analog optical power level going into another SONET mux a thousand miles away. If you feel like this is a nerd's joke that lacks a punchline, I'll spell it out -- similarly to the CD-R test, SONET recovers and regenerates the signal. There's no direct analog-to-analog transfer.

Rod, I'm not sure I understand what you mean by this:

"Was this some kid's science project?

If, by some ill-designed method, CD-R copies were made by a mechanical method (duplicating the media representation rather than the recovered & regenerated signal), then there would be a good chance that bit drift would corrupt some data eventually."

The point of the article was that after the guy burned 100 generations of cd copies, using his burner, the 100th-gen cd was a bit-for-bit copy of the first-gen cd.

For some reason, probably superstition, I always thought bit-rot would happen to data during multi-generational data. I think this was due to me forgetting about the whole point of CRCs.

I guess the science project comment sounded condescending; I didn't mean it that way. The tests described just seemed like a school science project to me.

My point was that, for this specific technology, the stored data is fully checked and regenerated for each copy. If copies were instead made mechanically, that is, directly duplicating the microscopically-sized burned spots from one CD-R onto another, the data would eventually degrade, because there would be no checking and digital regeneration to preserve the fidelity of the data.

Holy cow, Rod, I'm glad you said it, condescending-sounding or not.

Scout has been looking for an interesting project to add to her Space Camp scholarship application, something sort of atypical and eye-catching but not too very expensive and flexible time-wise (when I can supervise the goings-on).

This one is PERfect.

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