From: lull@acm.org (John Lull)
Date: Sat, 16 Mar 1996 18:52:41 +0800
To: jim bell <jimbell@pacifier.com>
Subject: [NOISE] NTSC color encoding
In-Reply-To: <m0txlRT-00090rC@pacifier.com>
Message-ID: <314a5cb4.141647874@smtp.ix.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain


On Fri, 15 Mar 1996 18:10:59 -0800, Jim Bell wrote:

> At 12:18 AM 3/16/96 GMT, John Lull wrote:
>
> >This is not correct.  I'd suggest you go back and re-read your NTSC
> >references.
> 
> If that's not correct, what is?  And it's been years since I read NTSC; I 
> don't even know if I now have ready access to the information.  Merely 
> saying that it's wrong isn't particularly informative, especially if you 
> choose to copy it to the list.

A detailed discussion of NTSC (or PAL, or SECAM, or any other video
standard) color encoding is hardly cypherpunks material.  I posted to
the list ONLY because I'd hate to see anyone rely on your posting.  A
simple heads-up warning should be enough for most people to realize
they need to look up a more authoritative source if they really need
to know how this stuff works.

If no one replied publicly to such inaccurate postings, the internet
would quickly degenerate to the "Net of a Million Lies" of fiction.
If everyone replied publicly and in excruciating detail to every
off-topic but inaccurate posting, there would be so much noise on the
list very little could be accomplished.  I should, of course, have
added [NOISE] to the subject line in my origial response, and for not
doing so I apologize to the list.

The color components in NTSC (there are 2 of them, not just one) are
carried as essentially double-sideband suppressed carrier signals at
the color subcarrier frequency, both phase-locked to the color bursts,
but with the two carriers in quadrature.  Although the sum of these
signals does vary in phase, it is CLEARLY distinct from a phase
modulated signal since it also varies in amplitude.  A phase-modulated
signal would not do so.

If you feel a burning desire to pursue this further, PLEASE take it to
e-mail.  I'll not be replying to any further posts to the list on this
topic.