Back-To-Back Recording

I'm thinking of adding a Roamio for OTA recording to supplement my DIRECTV system DVRs. One of the things that DIRECTV got right is that its DVR will only take up one tuner to record two padded shows back-to-back on the same channel.



Does the Roamio use one tuner or two to do this? My Tivo HD uses two. Since the base Roamio only has four OTA, this is probably a dealbreaker for what I want to do (which is basically move my OTA recording off the DIRECTV box and perhaps eventually cut the cable).



Thanks.