Steve Lefevre said:
I want to have it so I can use the video outs on two laptops, have one
laptop playing a DVD, which goes through the mixer to the projection screen,
and meanwhile I'm getting the next DVD scene ready. When it's at the right
point, I slide the slider over and now laptop 2 is on the projection screen.
The simplest thing to do is to just unplug the output cable from laptop 1
and plug it into laptop 2. This can be made a bit nicer with an SPDT
toggle switch - you can wire one up, or buy one in a nice box with the
video connectors as an "input signal selector" at Radio Shack for $20 or
so.
If you're lucky, when you switch from laptop 1 to laptop 2, the video
will be "seamless". What will probably happen is that there will be
a momentary glitch in the video - something like a bar rolling up the
screen, or a completely black or white screen for a second. If you're
not lucky, the projector will see the momentary lack of signal, switch
to blue screen, and refuse to display the video from laptop 2 for a
second or two.
If you can tolerate the glitches, doing the above is cheap. If you
want something a little smoother, you have to spend more money. In
short, the video outputs from the laptops have to be synchronized so
you can switch between them without glitches. This link has a decent
explanation, and a link to a chip that might be useful in building a
mixer:
http://www.epanorama.net/links/videocircuits.html#videomix
If this project is in any way related to school, you might find the
video production people (often found in the theatre, art, or media
departments, at the stadium, or in the "distance learning" office)
and see if you can borrow a mixer from them. Even if not, they might
be able to recommend an inexpensive product that will do what you want,
or at least tell you what catalogs to look in.
You _might_ be able to do it in software. If the video output comes
directly from the DVD drive, then probably not. But if the video is
read digitally from the DVD and then converted to analog by separate
hardware in the laptop, it might work. You'd have to figure out how
to get two DVDs hooked up to the laptop, or rip one of the DVDs to the
hard disk. You also need enough horsepower on the laptop to deal with
playing one DVD and cueing another.
I hope this helps!
Matt Roberds
