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Re: This can't be true...

bieling@terra.es wrote:

This is not so.  In all graphics modes, a color burst is present
(though it may not of "perfect" position or duration).  Almost
every NTSC device is *extraordinarily* sensitive to this color
burst, which is gated and used to phase lock a crystal oscillator
for chroma decoding.
In fact, there was an early change to the Apple II circuit to provide
more isolation when the color burst was switched off (in text mode)
so that TV monitors wouldn't pick up the tiny leak-through burst and
go into color mode!




As Don points out, only a *very* picky video processing system would
fail to lock to the Apple color burst.



As Don points out, "snob" "broadcast quality" equipment may not even
try to understand when they hear "toe-may-toe"... :-)

But then Apple technical writers could have better said something like
what you said : "the Apple IIe color burst is not of "perfect"
position/duration".
Instead, they say that "The Apple IIe does not contain the color burst
element of the NTSC video signal".


And I'm pretty sure that the exact duration or position of the Apple
color burst is not the real problem--I suspect it is the slight
departures from standard scan frequencies/durations, as Scott reported.


Furthermore, a *black and white* video signal can be fully
"NTSC-Compliant" *without* the color burst.


In fact, that's what *makes* it a monochrome signal.  ;-)


The phrase: "By modulating other portions of the video signal, the
Apple IIe simulates this missing information and allows an image to be
produced on a television". What does this mean ? this phrase is a
nonsense. It is not true either. What "other portions of the video
signal" can be "modulated" to "simulate this missing information" (the
color burst) ?

(this article could have been written much better by the csa2 staff)


Or anyone who understood the Apple II video signal--there were plenty
of them at Apple, so this must not have been widely proofread.  ;-)

-michael

Music synthesis for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
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