I'm trying to get my hands on (which probably means 'make') a video mixer, like a DJ mixer.
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.
Can this be a simple project? I'm a self taught computer geek, but I don't have very much electrical knowledge.
Steve, it won't be a simple job because you'll need to have the separate DVDs syncronized to the same master synchronization source, otherwise vertical and horizontal synchronization will be lost each time you switch. Consumer equipment usually lacks this capability.
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:
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.