Greetings,
I don't know if your question has been answered yet, but if not there are quite a few products on the market. I just picked up a little thing from ADS called the VideoXpress, and that will take a composite or Svideo input and run it straight into resolume. I used it to input the output of my switcher, which was taking a stream from resolume. It was pretty crazy, but it will take any composite camera input or DVD player, or whatever else you have. The best part is, that it is bus powered off the USB port and therefore doesn't need to be plugged in!
Anyway, ADS offers a wide variety of products much more powerful than that, if you need a little more robust solution.