Sluggish response when using console/tuner

[MHat]

I have an ATI TV tuner box for my PC, and recently hooked up my Xbox to it to play it on my monitor. When I started playing a game, the FPS called Halo 2, my controller response time was EXTREMELY delayed. This never happens on my TV, and I noticed this was the same problem I was experiencing while playing Splinter Cell on this device a while ago. What is going on? Is the video processing so delayed through the ATI device to my PC, that I am getting delayed controller response times?