Have you tried the Slackbuild? I installed it on 2 12.2 systems 2 days ago and both went of without a hitch.
Failing that, the svn version:
Code:
http://svn.mplayerhq.hu/mplayer/trunk
to check it out:
Code:
svn checkout svn://svn.mplayerhq.hu/mplayer/trunk mplayer
This is from the mplayer download page:
http://www.mplayerhq.hu/design7/dload.html
which also contains a link to a daily svn snapshot, so I'm not sure how you missed it.
Anyway, I'd try the slackbuild first, then try the daily svn snapshot, then svn directly, but mplayer can be a bit of a pig to compile sometimes.
cheers,