Well, HandBrake will encode a dvd to appletv format, but not sure what you are referring to by "upconverting". If you mean encode the output video at a higher resolution/bitrate than the source, you could do it with the HandBrake cli, but the macgui will not let you and for a very good reason. "Blowing up" the output movie past the source size is a total waste of time and file size, the atv and your tv already " upconvert " just as well and you don't have all of that wasted file size and bitrate.