Assuming the DirecTV remote takes 5 digit setup codes, then 20490 is the same as Video 0490. The leading digit implies the kind of device-- 0=Cable, 1=TV, 2=Video, 3=Audio.

0490 (or 20490) is Panasonic IR protocol with device 176. It definitely will control the DMR-E55, and just about any other Panasonic DVD/PVR. However, the DVD can be set up to use three (maybe more) subdevices. I don't know how those are set up on the DVD, but 0490 will control only the base (as shipped) subdevice. I'm sure the DVD manual will tell how to set the subdevice. Maybe it calls it a channel.