So no matter what, 720p videos will not play on the N900 using Maemo5 OS unless you resize on the fly. (which can be done using mplayer) Then mplay does play 720p video files. However, it plays it at like 1-2 fps at best. Heck, N900 even struggles with 480p AVC files right now. N900's hw is more capable than what it can do right now but we don't have the drivers / codec to take advantage of hw acceleration.