[vorbis] Copy protected CDs (off-topic)

[Frank Klemm]

::  > On Mon, Dec 18, 2000 at 02:52:42AM +0100, Segher Boessenkool wrote:
::  > > 3) Use some different kind of plastic for the cd, a kind which
::  > >    will not be easy to the cdrom laser, but still is ok to a cd
::  > >    laser (cdrom lasers are a different color).
::  > >
::  > What's the difference between 780 nm (CD player) and 780 nm (CD-ROM drive)?
::  
::  As far as I know, higher speed cdrom drives use shorter wavelength
::  lasers to reduce the amount of read errors. I could be wrong, of
::  course; I don't know cdrom hardware that good.
::  
Some DVD drives are using green Layer light to also read out CD-ROMs and CD
DA. This reduces contrast for pressed CDs (no lambda/2 interference) and
especially for CD-Rs (dye absorption maximum), because they are optimized
for 780 nm.

Better DVD drives have 2 lasers, one for CDs and one for DVDs.


-- 
Mit freundlichen Grüßen
Frank Klemm
 
eMail | pfk at uni-jena.de       home: pfk at schnecke.offl.uni-jena.de
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