Path: cdrom.com!barrnet.net!decwrl!hookup!europa.eng.gtefsd.com!howland.reston.ans.net!news.cac.psu.edu!monitor!krudolph
From: krudolph@sun.com (Ken Rudolph)
Newsgroups: alt.cd-rom
Subject: Re: CD Space
Date: 31 May 1994 18:03:45 GMT
Organization: HMC
Lines: 27
Distribution: world
Message-ID: <2sfu61$vro@hearst.cac.psu.edu>
References: <15448@m1.cs.man.ac.uk>
Reply-To: krudolph@cit.hmc.psu.edu
NNTP-Posting-Host: monitor.cit.hmc.psu.edu

>The answers of about 660 to 680 Meg are about right.  This corresponds to the
>72 minutes you can fit on an Audio CD if you keep exactly to the specs.
>I do have, however, a 79 minute CD.  They lowered the 'pitch' ... the distance
>between successive lines of the spiral ... to do this.  I see no reason why
>they shouldn't try the same trich on data CDs.

They CAN do the same thing on data as on audio CD's. At the physical level,
there is really no difference between the two.  Two of the more obvious problems
with doing this are:  
1) It's not within the red or yellow book
specification, therefore you buy at your own risk. As you approach the
outer diameter of the disc, the data becomes more difficult to read as
well as reproduce. That's why there IS a specification for these
parameters.  
2) As you lower the track pitch (put more music/data on
the CD), you have a greater chance of exceeding the tracking mechanism
tolerances built into every player. Some players and player
technologies handle this better than others. The one's that don't,
simply can't read the information. The players that can read it, usually
exhibit degraded seek times, which can have a negative effect on some applications
(in the case of CD-ROM).

The "official" spec for audio (and data) is just over 74 minutes. You can put 700
megs of uncompressed data on a CD-ROM, just as you can "squeeze" 80
minutes of music on CD AUDIO.  In both cases, let the buyer beware!

Ken