Actually the audio and video inputs are selectable for each function, but each input can only be used once. So you could do it, but it will require some tricky wiring. As one example (the most likely one that would work) you likely have set up now one HDMI input for the cable box and one other for the Blu-Ray player. So, if your cable box has an old style RCA video out (or component out, or S-Video), and your Blu-Ray has stereo audio out (again, RCA) you could run those into a third function on the receiver. However, if the Denon doesn't have an input natively set up for all RCA, be very careful when adjusting the inputs in the menu. If you select one that is currently in use, even in passing, it will screw up all of the other inputs and you will have to reset everything (don't ask me how I know). I hate the menus on the Denon so bad that it has me looking at other receivers.
This may or may not also require you running another wire from the receiver to the TV (RCA video, component video or S-Video) and selecting that input on the TV when you wish to use that setting. That depends on if your receiver upsamples and sends analog video through the HDMI cable (some do, some don't).
