The graphic card might have input support, if the card has ViVo
then input mode is supported (ViVo not Avivo).
You need to check your brand and model (I'm not sure but many ATi cards support ViVo, dunno about nVidia).
ATi Theater/AllInWonder models have video in for sure, in either cases you need special drivers, WDM ones, I think.
Hope this helps.