Date : Mon, 06 Mar 2006 20:42:42 +0000
From : Phil Blundell <philb@...>
Subject: Re: Warning: Sad case on list!
On Mon, 2006-03-06 at 19:44 +0000, Jules Richardson wrote:
> Not sure as such - I was thinking Econet, but after talking to Mike the other
> weeks about his fractal array maybe the User port's the way to go - assuming
> that a suitable multiplexer can be bodged at the controller side.
>
> Note I'm not looking for real-time video or anything :-) Given Econet speeds I
> think I figured out that I might be able to get an image from camera to image
> wall in about ten seconds - which with some creative "fading in" from previous
> image to current should be about the right sort of time. If it was instant
> then it just looks like it's all being faked by a PC behind the scenes, and
> much longer than that and people would just get bored!
Right, yeah, that's about what I figured. I don't think you'd need a
terribly powerful CPU to deal with that kind of data rate (which only
equates to a few tens of kilobytes per second) though I guess it depends
on how intensive your dithering is.
> Hmm, I think the ones I've come across in the past tend to be 16 colour only;
> ideally I'd like something that gave we a 256 colour image (at least!) and at
> least the theoretical max resolution of the image wall (640x1024). That's
> possibly outside the capabilities of the average "home market" Acorn add-on of
> the time. Still, needs looking into at some point...
That does sound a bit much for a commodity digitizer from that era,
yeah. Even today I suspect a lot of PC addon type digitizers will have
trouble coping with 1024 lines, though I guess there must be HDTV
versions around by now. What are you planning to use for your video
source?
If you don't mind using a bit of modern technology, it probably wouldn't
be terribly hard to build a digitizer based around an SAA7111 or
something that you could interface to pretty much anything you wanted.
It'd almost certainly be easiest to have a full-frame buffer on the
digitizer board; that way your host CPU could read the data out as
slowly as it wanted.
p.