If you do end up building a custom solution, I have a feature request :-) It would nice if the device was also a frame grabber that could, under command, snap one or more frames of the legacy video and export it over USB perhaps.
This would allow us to document operation of legacy software with high quality frame grabs since persumably you'd have access to the image in a relatively good quality domain before you turned it into DVI/HDMI or whatever. Chris -- Chris Elmquist NØJCF