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- Xref: sparky sci.electronics:13314 rec.audio:10834
- Newsgroups: sci.electronics,rec.audio
- Path: sparky!uunet!cis.ohio-state.edu!zaphod.mps.ohio-state.edu!uunet.ca!imax!dave
- From: dave@imax.imax.com (Dave Martindale)
- Subject: Re: Life after CDs
- Message-ID: <1992Jul25.193359.352@imax.imax.com>
- Organization: Imax Corporation, Mississauga Canada
- References: <Brr3A6.5IA@news.cso.uiuc.edu> <1992Jul23.041115.20377@bilver.uucp> <25fg02Og1bxl01@JUTS.ccc.amdahl.com>
- Date: Sat, 25 Jul 1992 19:33:59 GMT
- Lines: 27
-
- bill@bilver.uucp (Bill Vermillion) writes:
- >
- >then Sony and Philips got together and standardized on the
- >current 12cm disk that sped'ed out at 74 minutes.
-
- ptt00@DUTS.ccc.amdahl.com writes:
- >Does anyone know for sure the absolute maximum playing time of CDformat ?
- >
- >I had always heard this 74 minute nonsense, then "Electric Ladyland" came
- >out on one disc at 75:25. A couple years ago I got one by the Mexican
- >band "Iconoclasta" that clocked in at 80:20. What Gives ?
-
- The CD standard specifies a nominal value for various parameters of
- disk mastering, plus maximum and minimum values. The linear velocity
- is supposed to be some value, plus or minus a tolerance. The track
- spacing is also supposed to be something plus or minus a tolerance.
- That's probably true for the width of the area containing music as
- well.
-
- If you set up your mastering lathe to exactly meet all the nominal
- tolerances, you get 74 minutes of recording time. But if you fudge
- them towards on end of the limits, you can get more. Dropping
- the linear velocity gets more playing time, as does reducing the
- track spacing. The result is a disc that is still "legal", but
- more difficult to play. A CD player with marginal data separator
- or servo system (either due to design or age) may not play this
- CD reliably, while it will still play "normal" ones.
-