centering mplayer

I want to play videos in the center of my screen. I don't want to run them full-screen because for some videos that takes too much CPU time and gets video and audio out of sync and for some other videos the resolution isn't high enough (anything scaled up by more than a factor of 2 looks bad). There are mplayer options for putting the window at a specific position, this would be fine if I had many videos with the same resolution. But I want to play arbitrary resolution videos in the center of the screen. Any ideas on how to do this? -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/