I can't confirm if they are both active at the same time, but last night I connected both HDMI and component to the same TV. When I cycled between inputs on the TV, both inputs from HDMI and component were working. So unless the component video output shuts off when the HDMI "handshake" occurs I would say they are both active at the same time. If I get some time I will try hooking up a second TV and test this out.
3/17/10 at 8:58am