Re: Video Overlay Card

[mnementh@netcom.com (David R. Villegas)]

dempson@actrix.gen.nz (David Empson) wrote:
>Radagast <tschmidt@magnus.acs.ohio-state.edu> wrote:
>> What good is a Video Overylay Card on a IIGS?  I may be able to get
>> one for a decent price.  So what would I be able to do with it?
>
>The Video Overlay Card is a video mixing device: you can combine an
>input video signal with computer-generated video, and output that to
>another device.  To make full use of it, you probably need two video
>recorders, or at least a video camera and a recorder.  You could do a
>reasonable amount with a video camera or recorder and a monitor on the
>output, but idealy you should use a video recorder on the output.
>
>The most obvious use of it is to add computer-generated subtitles to a
>video.

And you can watch TV while you type away on your computer.
You can also make educational programs that combine video and computer
graphics, especially if you have a Laserdisc player attached to the computer.

The VOC also has an interlaced graphics mode with doubled vertical
resolution, lets you have two different monitor displays, and has an expansion
bus if you want to build things like a graphics card or a video digitizer.

>> What software makes use of it?
>
>Any software that uses super hi-res mode (and other modes?)  Some
>programs are better than others.  In particular, 320 mode works better
>than 640 mode, and it helps if you can generate large areas of the
>same colour on the screen, since the VOC operates on a "key colour"
>scheme - the key colour becomes transparent, allowing the video source
>through.

I've only seen two programs specifically use the VOC.  However, overlaying
graphics or text on video works with any software whatsoever.  You can
control the degree to which the key color is transparent and ditto for
all the non-key colors.