Re: 6502 core / 128 mode (re: J-Board) (fwd)
Date: 2001-03-16 01:51:33

On Thu, 15 Mar 2001, Bryan Pope wrote:

> > 
> > >>>>> "BP" == Bryan Pope <> writes:
> > 
> > BP> I believe it can also be used to replace a color in the
> > BP> video stream with computer graphics. (The weatherman in front of
> > BP> the animated weather map).
> > 
> > No, that's called chroma keying. Same principle though.
> > 
> But doesn't a genlock do both video overlay and chroma keying?  Or do you 
> need a separate piece of hardware for chroma keying?  It has been a *long*
> time since I worked with this type of equipment.  But we did use Amigas! :)

The amiga video port has a /PIXELSW as well as a XCLKEN signal pair.  If you
separate the sync from your video signal, take the horiz and synthesize
28mhz (?) from it, and feed it into the video port, and take your separated
horiz and vert sync's and feed them into the output with XCLKEN, the amiga
will switch its internal oscillator off and use yours so it can sync to your
signal.  Now all you need to do is switch between the amiga and your video
signal. ;) Thus, PIXELSW.  Whenever a non-background color is displayed,
pixelsw indicates that amiga video is active.  Voila. Genlock.

Amigas have been able to do chroma keying via an addin card and time base
corrector.  This, however, isnt stock hardware.


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