Date: Sun, 17 Mar 2002 07:53:16
From: "neil barnes" <[EMAIL PROTECTED]>
Subject: Re: making MP3s to fill my new HDD [LIB]

>Date: Sun, 17 Mar 2002 06:13:05 +0000
>From: "Matthew Hanson" <[EMAIL PROTECTED]>
>Subject: Re: making MP3s to fill my new HDD [LIB]
>
>(Caution: Absolutely no Libretto content here...  )

>>There will ALWAYS be a way of copying the audio. After all, if you wanted
>>to push it to the extreme, you could always play the CD in a half-decent 
>>CD
>>player, plug the digital out (or analogue out if they've protected digital
>>signals) into another device or a computer then just record. No way they
>>can stop that ... <

You will always be able to read a digital data stream...after all, if you 
can't decode it, you can't play it, so what's the point. However, the sp-dif 
domestic format includes a copy inhibit bit which recording equipment is 
*supposed* to respect. I suppose the US govt will require that unstreaming 
chips *must* obey, but it won't make any difference - professional systems 
always ignore the copy bit.

>
>Heh...  yeah...  that was the very first thing I thought when I read that
>article...  No stoppin' tappin' into that digital stream with a fancy lure!
>
>>schemes like the Anti-VCR stuff on DVDs won't fix that for instance 
>>because
>>there is no intelligence in the recorder that can be 'fooled' that can't 
>>be
>>'turned off'.<
>
>I had a fairly knowledgeable friend who works with videocassettes tell me
>that some new (in the past many years) VCRs (don't know about DVD players)
>ARE in fact made with copy protection that is written into SOME
>videocassettes  ...  and so keep them from being copied.  Know anything
>about this Raymond?
>

Again, there are various mechanisms to upset video recorders. The simplest 
is to put a varying height pulse in the frame blanking pulse - on record, 
most domestic vcrs do an automatic gain control based on the height of the 
sync pulse in blanking - so the brightness of the rest of the frame is 
incorrect. Doesn't stop it being recorded, but makes it unwatchable. Of 
course, a video signal processor will chop that straight out again...

You could use the same mechanism on a DVD to make it unwatchable on tape, 
though the easiest way of implementing it would be to drive the output chips 
directly depending on the copy bits.

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