Re: Apple ][ to VGA monitor adapter board - looking for best color decoding method

[MdntTrain <js@cimmeri.com>]

On Apr 4, 5:02 pm, ferd...@gmx.de wrote:
> I've been working on a board to double each line of the Apple //e's
> video output so that it can be viewed on a normal VGA monitor.  My
> goal was the perfect picture quality. To yield it, I sampled the Apple
> video signal with the original Apple clock, stored it in RAM and
> displayed each line twice with double speed. This works so far (except
> for one timing problem that can be fixed by touching the correct
> line... this is going to be fixed) and produces an extremely crisp
> picture. Especially the 80-col mode is way better readable because the
> lines aren't that far apart as on a monochrome monitor.
> So far, so good. Now the problem starts: color. The signal needs to be
> converted to RGB somehow.
> I tried:
>
> 1. Latch the video signal 4 times at different phases to  COLOR
> REFERENCE. (7M rising, 14M falling with 7M high, 7M falling, 14M
> falling with 7M low - note that COLOR REFERENCE becomes 7MHz after the
> conversion). These 4 signal are mixed to form the 3 colors. This
> method gives exact reproduction of the 15 LORES colors (I designed it
> to do so) but blurs the picture in HIRES.
>
> 2. decode the color as above, but gate it with the monochrome signal,
> so that a green horizontal line actually becomes a dotted line. With
> some displays this looks really nice, but it sometimes produces ugly
> color fringes on white areas.
>
> The Apple //e's PAL encodes uses a circuit with a quad D-FF, but I
> don't know how it is wired.
> So I'm looking for the schematic of the //e's PAL encoder or the PAL
> color card for the ][.
>
> BTW: I'm missing both the Eurapple jumpers and the 14M/Graphics time
> signals on Slot 7 in the Apple //e PAL. I had to jumper them directly
> from the main board.
>
> Ferdinand Meyer-Hermann

  Just curious, is there any way to easily get the separate Y + C out
of a II?   Or are Y+C somehow generated as one?   I've yet to examine
this... but there are a variety of very good svideo->vga converters
already available used, inexpensively... a route I might prefer to go
as I own a few.

  Thank you,
     JS