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From: rbl@nitrex.UUCP
Newsgroups: sci.electronics
Subject: Re: 3800 Hz notch filter [will] be used on CD masters
Message-ID: <472@nitrex.UUCP>
Date: Sat, 6-Jun-87 17:09:53 EDT
Article-I.D.: nitrex.472
Posted: Sat Jun  6 17:09:53 1987
Date-Received: Sun, 7-Jun-87 19:49:06 EDT
References: <598@neoucom.UUCP>
Reply-To: rbl@nitrex.UUCP ( Dr. Robin Lake )
Organization: The Standard Oil Co., Cleveland
Lines: 40

In article <598@neoucom.UUCP> wtm@neoucom.UUCP (Bill Mayhew) writes:
>Hi,
>
>	I just heard from some people that got back from the
>Chicago CES, some of the details of the proposed new standard to be
>employed for production of source material (compact disc records)
>and digital audio tape (DAT) machines.
>
>	From my understanding, what will possibly be done is to
>master CDs with a narrow band notch set for 3800 Hz as the material
>is mixed down into final form for the consumer's copy.  DAT
>machines are to be equipped with a so-called spoiler chip that will
>monitor three narrow bands of 3800-, 3800, and 3800+ Hz.  The idea
>is that if the chip detects energy in the two outer bands and none
>in the middle band, that it will shut down the recorder, as
>"obviously" a pirating event would be under way.
>
>The question for the net is, just how wide is the missing mateial
>notch going to be.  Supposedly, people that have heard trial
>recordings of the processed material claim that it is very
>noticable on things like classical and jazz recordings that feature
>solo instrument passages more than rock does.  Apparently, some
>notes are curiously dull sounding on piano passages due to the
>action of the notch filter.  Vocals are also apparently affected.
> ...
>Bill Mayhew
>Division of Basic Medical Sciences
>Northeastern Ohio Universities' College of Medicine
>Rootstown, OH  44272  USA    phone:  216-325-2511
>(wtm@neoucom.UUCP   ...!cbatt!neoucom!wtm)


In the latest issue of MART, a trade magazine for electronics/appliance
dealers, an article mentioned that CBS noted that in "some passages" the
notching would be eliminated.  They interpreted this as CBS admitting
that the anti-copy technique would, in at least certain sections of music,
corrupt the sound quality.

Rob Lake
decvax!cwruecmp!nitrex!rbl