newbie: video switcher controlled by usb or midi or software?

[neuronetv]

for a project I'm doing I need to get a hardware video switcher, I'm only working with standard composite (the yellow, red, and white phono connections) and I only need to switch between two channels (pre-recorded video and live camera) and I was wondering if anyone knows of a switcher that will work via usb or midi signal or by software control from a pc. Thanks for any help.