Ive been reading about all the Dolby Digital Live talks going around here lately, and decided its time for me to learn what all this stuff, and all the audio components out there. I confused on something my motherboard has. My motherboard has the built in Realtek 880 audio in it. It has both a S/PDIF in and out connector. I know the S/PDIF out output goes a receiver. What does the S/PDIF in input do?