Has anyone experimented with playing a fullscreen 1080p video on a GUI texture? It's easy to do, but a 1920 x 1080 fullsreen video is choppy at best. I'm using a .MOV that's honestly a pretty large file (I'm picky about quality). Target is a standalone player on Windows 7 x64 quadcore w/ 8 Gigs of ram and a high end graphics card so I can tell you that the hardware is not lacking. Any ideas on compression settings etc to get great quality but smooth 1080p fullscreen playback?
I'm actually very surprised you managed to import a 1080p video in Unity. The best I managed to do was a 720p.
To answer your question, Unity recompresses all imported videos in its own format, using Ogg Theora. So if you import your video using the best quality available (i.e. push the little slider aaaaaall the way to the right), then the result is going to be the best you can possibly achieve in Unity.
If that's not good enough for you, then you're out of luck, I'm afraid, until Unity improves video playback, but considering their main target market (mobile devices, webplayers...), it's massively unlikely in the short/middle term.