I don't think we have had much luck getting the TVOut hardware working yet. Alex has been working on it (working with our internal engineers) as time permits but it has been a lower priority than getting the 3d engine going for 6xx/7xx so we can push ahead with 2d, 3d and video acceleration for those chips.
My understanding is that radeon supports TV today but only with pre-5xx hardware, which has a very different TVOut implementation.