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From: farren@well.sf.ca.us (Mike Farren)
Newsgroups: comp.sys.amiga.tech
Subject: Re: CD-ROM vs. CD Players
Message-ID: <21928@well.sf.ca.us>
Date: 3 Dec 90 15:25:07 GMT
References: <90335.112615AXN100@psuvm.psu.edu> <1990Dec2.073639.22387@zorch.SF-Bay.ORG>
Lines: 34

xanthian@zorch.SF-Bay.ORG (Kent Paul Dolan) writes:

>In article <90335.112615AXN100@psuvm.psu.edu> AXN100@psuvm.psu.edu writes:
>However, if I understand it right, in audio CDs, it is the _length_ of
>the "on" area or "off" area along the track, rather than its mere
>presence (as in the data bit on a digital CD-ROM), that is important,
>sort of like the zero crossing distance, rather than the amplitude, is
>the real signal in an FM radio signal, and it is this ability to ignore
>signal amplitude that lends the audio CD its enhanced sound reproduction
>ability.

>If this is right, you can't use a CD player to read digital CD-ROMS
>without a whole separate signal extraction "mechanism" behind the read
>laser.

>If I'm all wet here, I'm sure someone in the group can correct/expand on
>this.

You're all wet, Kent :-)

The fact is that the data is _encoded_ onto the CD by way of the length
of the "on" or "off" areas, but that's not really all that much different
from something like MFM encoding for a disk.  It's one level down from
anything you need to concern yourself with - both CD audio and CDROM do
this, and both give you pure digital data once you strip off the encoding.
The format for the data that comes out, however, IS significantly different
between the two different media, though, so you might have some problems
there.

CD's sound reproduction ability is simply due to their 16-bit A/D circuitry,
leading to a 96db dynamic range, far superior to ANY analog recording
mechanism.
-- 
Mike Farren 				     farren@well.sf.ca.us