Re: HDMI Video/Audio Card

[Daniel Kruszyna <dan@krue.net>]

Charlie <charlieDOTd@vereyezon.net> wrote:
> The picture I'm getting for normal 640 and 320 GS modes is as good as 
> any I've ever seen.  Better than the Apple IIgs RGB monitor if you can 
> take the facts that there are no side borders and the picture is so 
> sharp that there is no dithering.  The 320 Fill mode has a bug (I'm 
> working on that).  Weird modes that do over-scanning don't work 
> correctly and for some reason 3200 color pictures are a mess.

How do you convert to VGA timing? Do you reimplement the IIgs video scanner
into a line or frame buffer which is then rescanned at the VGA frequency?
Or do you directly scan video ram with the VGA scanner?

I'm not saying whether this is worth it or not, but to get things "just right",
you need to duplicate the IIgs video scanner exactly. This includes reading
palette and pixel data at the correct times. 3200 mode depends on software
modifying the palette tables while the screen is being drawn.

Also, what do you refer to by "overscanning modes"? Border tricks? If so, then
these also depend on software modifying the border register while the screen
is drawn.

Even if you duplicate the video scanner exactly, it is not synchronized to
the MegaII scanner which the software is reading. You can synchronize with
the SYNC signal, but it's only available on slot 7, which doesn't have the
also necessary M2B0 signal. The Video Overlay Card is in a similar situation,
but in that case, you can connect the IIgs composite out to the VOC to cause
it to sync.

-- Daniel