I really hope that somebody can clear up a number of questions I have about HD video playback. I'll start by saying that I recently acquired a 1080p copy of several movies and they have a lot of trouble on my mythbuntu system. I have no problem with 720p videos on the mythbuntu computer and when I play the 1080 files in windows on a different computer with slower hardware they run perfectly fine. I've read many forums and found lots of questions with few solutions, so I hope this forum can answer some questions for me:

1) Is it possible to compile from source the newest x264 codec for use with mplayer?
2) Is it possible to compile from source mplayer itself
3) Will either of these improve performance of my video playback
4) Is there a way to tell mplayer to use both cores of my processor for decoding?
5) Is it true that linux does not have hardware acceleration for x264/h264?

I use mplayer without the GUI, so please provide answers that can be used from the terminal

thank you