You didn't reveal what the video source was so I can't give a good example. Here's a HDMI video processor.
http://www.gefen.com/kvm/ext-hd-vwc-144.jsp?prod_id=14708
Bob
I have four LCD monitors and want to mount them together to become one large monitor, are there devices that will take a single input signal and split it to four outputs in this way?
Google hasn't been helpful, possibly because I didn't know the correct terminology, or possibly because this is a really stupid thing to want to do...

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic