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Path: utzoo!utgpu!water!watmath!clyde!ima!haddock!wolfgang
From: wolfgang@haddock.UUCP
Newsgroups: sci.electronics
Subject: Re: 3800 Hz notch filter [will] be used on CD masters
Message-ID: <520@haddock.UUCP>
Date: Mon, 8-Jun-87 00:41:54 EDT
Article-I.D.: haddock.520
Posted: Mon Jun  8 00:41:54 1987
Date-Received: Tue, 9-Jun-87 00:52:12 EDT
References: <598@neoucom.UUCP>
Reply-To: wolfgang@haddock.ISC.COM.UUCP (Wolfgang Rupprecht)
Organization: Home for Wayward Programmers
Lines: 14
Summary: copy-protection protection


	What would prevent someone from copying a CD by mixing a bit
of white noise in with the program material? I would imagine that a
very little bit of interstation static from an AM or FM radio would
suffice to fill in the bottom of the 3800 hz notch. (I small bit of
noise would actually help reduce the distortion caused by digital
quanization. It might actually make stuff sound a bit better.)

Does anyone know the full details of this CD labotomization scheme?
Is it the absolute value of energy at 3800 hz or the ratio of energy 
at 3800 hz. vs the rest of the spectrum? How much energy must be present 
at 3800 hz to reset the copy protector?
-- 
Wolfgang Rupprecht 			haddock.ISC.COM!wolfgang