You misunderstand as it's not another application
I'm talking about a directshow capture filter to use as channel within MC television. I can already use the microsoft provided one for the card but that only supports stereo audio and doesn't expose the colourspace in a way that lets a renderer understand it, you have to use the api provided by the card manufacturer to do all that. Hence write one and then be able to use MC to fully access the card capabilities.
Put simply, it's exactly what Yaobing is doing for the blackmagic cards (which I don't use because they have limited support for the resolution/frame rate output by my cable box. I can't imagine why you'd want to restrict support to a particular card but obviously it's your software so that's your choice.