While in Capturemode, visit the Devicesection of the Elgato Game Capture HDsoftware.
The name of your device, "Elgato Game Capture HD", will appear, along with the current resolution.
To find out more about the incoming video, press the blue circle with an "i"inside of it.
A small pop-up window will appear, listing the Input, Output, and Audiospecifics.