On Wed, 28 May 2003, Steve Bell wrote: > FWIW, I occasionally send CDs to Stebbings or Software Images to be > duplicated onto pressed CD's. They accept CD's written at only 1-2x. They > 'clover check' (whatever the heck that is) all CD's before making the glass > master, and they find that 4x+ contains too many errors. > > I also find with the pitch-shifting CD decks, (like Pioneer CDJ's, for > beatmixing/dj'ing), that anything written above 4x sounds much more digital > when using the pitch correction and jog wheel. I don't know the technical > reasons for that. But if you heard it, you'd agree. > > That's not to say that I can't write an audio CD at 32x which plays quite > merrily in antique home CD player and sounds fine. But for flash trickery > and audio stability, it seems slower is better.
Consider first the two main types of CD's: data and audio. For a data CD "you" have 2 levels of error correction while for audio there is only one. You can check the errors on level 2 on a data CD with something like: readcd -v dev=n,n,n -c2scan (from the cdrecord package) However reading the level 1 errors require intimate knowledge of the driver, i.e. specialized software (IIRC some/one brand was providing such software) You should never get errors at level 2 (otherwise your data is toast) while you will always get errors at level 1. Traditionally the CD players incorporated only level 1 correction while the computer drivers needed both (one reason for which they were more expensive). That may not be the case any longer due to the fall in the price of the units (they may be using the same drives/chipsets) But an audio CD does not have the level 2 error correction. For the same reason you can't make a perfect copy of an audio CD even if it's digital media, try to read them several times and compare the result. It may be that at higher write speeds you get higher level 1 errors and thus the artifacts you are hearing. Cheers, -- Ryurick M. Hristev mailto:[EMAIL PROTECTED] Computer Systems Manager University of Canterbury, Physics & Astronomy Dept., New Zealand
