Re: Once upon a time, there was a device...

["Michael J. Mahon" <mjmahon@aol.com>]

Liam Busey wrote:
> A.J. wrote:
>
> > ...that allowed Apple IIGS RGB signals to be converted to S-Video.
> > Does such a device still exist?
>
>
> I saw this in the CSA2 monitor FAQ. I have no experience with the
> product.
>
>
> Liam
>
>
> **********  excerpt from CSA2 monitor FAQ *************
>
>
> From: Jim Krych (ab453@cleveland.Freenet.Edu)
>
> 028- Is there a high-quality replacement for RGB monitors?
>
>      Yes. It's called the "VideoTurtle." (What follows comes from a
> Video
> Turtle advertisement.)
>
>      The VideoTurtle is a product that converts your RGB signal, known
> as TV
> RGB-15.75KHz scan rate for NTSC, into S-Video!  S-Video is an enhanced
> form of
> TV with better clarity and resolution than the "TV" we are all familiar
> with.
>
>      With your computer, the VideoTurtle, and an S-Video equipped TV,
> you get
> equal or better display quality, than your old RGB monitor. Not only
> that, you
> get a much bigger and eye-pleasing display, and a TV to boot!
>
>      The VideoTurtle, from Turtle Enterprises, can be purchased for
> $149.95
> from one of it's authorized distributors, such as Tex Comp Ltd. To
> order all
> 1-800-846-3474. For technical information on TV RGB systems we haven't
> mentioned, or general technical help, call 1-626-967-3341. Turtle
> Enterprises
> can be reached via email: videoturtle@hotmail.com

It is incorrect that this device can produce "equal or better quality
than your old RGB monitor" (unless your RGB monitor is pretty bad ;-).

The S-Video Chrominance signal is encoded on a 3.58MHz subcarrier, and
so the color resolution is subject to exactly the same limitations as
composite video.  The Luminance signal is not necessarily band-limited,
so luminance reaolution can be excellent (for text, for example).

But anytime that there the contrast between adjacent pixels is in their
color, not their intensity, the contrast will be much reduced by the
band-limiting chroma encoding of S-Video.

-michael

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

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