This is actually a rather involved thing that you want to do here. Short answer is that you really need a presentation switcher or something similar that uses F

This is actually a rather involved thing that you want to do here. Short answer is that you really need a presentation switcher or something similar that uses FPGA. If you want to roll your own, you can do it, but it's probably not gonna be worth the time investment. NETV2 (Libre mode) is probably the best bet for hardware that will both do the job and has at least some example stuff that will be similar. It's FPGA based, but it will require a lot of effort to implement. Other than that you are looking at the HDMI or DVI TxRx cards along with an FPGA dev board. Terasic's Altera boards and expansion cards, for instance will do the job and they offer VGA, DVI and HDMI interfaces for a large number of their dev boards. Anything along this vein will cost a lot more than NeTV2 IMO If you want to rely on something for a large commercial public presentation, I really wouldn't hack something together. Just buy a presentation switcher.