Re: Using IIgs with VGA monitor - how to go?

["Bill Garber" <willy46pa@comcast.net>]

Here's a goodie. $99.00

http://www.viewsonic.com/products/video_box_vb50hrtv.htm

Bill @ GarberStreet Enterprises
http://garberstreet.netfirms.com


Michael J. Mahon <mjmahon@aol.com> wrote in message
20030404150251.28474.00000529@mb-fv.aol.com">news:20030404150251.28474.00000529@mb-fv.aol.com...
> Scott Alfter wrote:
>
> >In article <9G5ja.33187$7Im.15777@news04.bloor.is.net.cable.rogers.com>,
> >Glenn Jones <rg.jones@rogers.com> wrote:
> >>"Volkmar Friauf" <vf@apple2.com> wrote in message
> >>news:b6hisl$5a4p8$1@ID-60882.news.dfncis.de...
> >>> recently, picture quality of my IIgs Color monitor is degrading
rapidly,
> >>> so I've been looking for an alternative. Since I have a fine VGA
display
> >>> for my PC, I am looking for a way how to use that display with my IIgs
> >>> (possibly with a monitor switch so I easily switch between IIgs and
PC).
> >>
> >>Slightly off topic ....
> >>
> >>I have a laptop that has s-video in and s-video out.. It also came with
a
> >>s-video to composite conversion cable.
> >>
> >>I thought what the hay... so I conected up the cable...fired up MGI
> >>Videowave and there in the preview window on the LCD screen was the IIGS
> >>display.
> >>
> >>Monochrome looks great .... colour on the other hand was pretty bad...
by
> >>toning down the brightness and colour level I could make the Desktop
useable
> >>but with very little colour.
> >
> >If there's a way to extract S-video from a IIGS, that might be doable.  I
> >don't have a schematic for it, but somewhere in the process of converting
> >analog RGB video to composite video, the Y and C signals that are mashed
> >together to form a composite signal must be present.
> >
> >Start with the four signals on the RGB connector: red, green, blue, and
> >composite sync.  First, the video hardware converts RGB to YCbCr. If you
> >mix Y with sync, you could take these three signals and get the same
> >component video that your DVD player produces.
>
> And for the best quality, this is where you should stop and connect
> to a high resolution video monitor.  All component video signals are
> baseband, and no intrinsic bandwidth limits apply (though a monitor
> may limit them).
>
> >  Combine Cb and Cr and you
> >get C, which is one of the two signals in an S-video connection (the
> >previously-mentioned Y/sync combo is the other signal).
>
> And you do this by using the Cb and Cr baseband signals to modulate
> a chroma subcarrier at 3.58MHz, so that their bandwidth is intrinsically
> limited.  This is the end of high-definition color information.  (Though
> the baseband Y signal will still make crisp monochrome.)
>
> >  Combine the two
> >S-video signals together and you get composite video.
>
> And also require a very high quality filter to remove the modulated
> chroma subcarrier from the luminance signal without seriously
> limiting its bandwidth.  Practically speaking, there are no such
> designs, since composite video is "known" to be band-limited to
> 4MHz to allow for the 4.5MHz sound subcarrier in broadcast TV.
>
> >I don't have a IIGS schematic, but if these signals are available at some
> >point where they can be tapped off and run to a connector, you could get
> >S-video to your other computer's TV-in jack; this would be of much better
> >quality than composite video.
>
> For monochrome signals, but color information is still band-limited.
>
> >  Another option (probably easier than hacking
> >at the motherboard) would be to build something that plugged into the RGB
> >output jack and provided component and S-video outputs.  If somebody
makes a
> >13" TV with component and/or S-video input, this could be a suitable
monitor
> >replacement.  (Component would be best, but S-video should be pretty
> >good...when I switched my TiVo from composite to S-video, I saw a big
> >improvement in the clarity of its menus.)
>
> Yes, the separate, higher bandwidth luminance signal will sharpen
> things up a lot, but the chroma information is still quire smeary.
> This is clear for any fine detail in color, such as colored text.
>
> >(FWIW, there's already a product on the market (the Video Turtle) that
> >converts RGB to S-video.  At $150 (according to the information I found),
> >it's still fairly spendy.)
>
> Conversion of RGB to component video should be almost a passive
> circuit, requiring buffer video amplifiers at most.  The cost should be
> under $10, which means it ought to be available for $50 if anyone
> builds it.
>
> -michael
>
> Check out amazing quality 8-bit Apple sound on my
> Home page:  http://members.aol.com/MJMahon/


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