Just as a further datapoint:

I've noticed, too, that the sound can drain a lot of the performance
from mplayer.  I first found this when I didn't let it drop any
frames.  The audio got far enough out of sync that the audio was
dropped.

I've also noticed that switching the audio and video ouput drivers
can affect performance.

I've also found that some options that seemed "good" at one time
can be "bad" later.  (I don't know if I've just noticed, or become
more sensitive to, some performance issues, or if mplayer has degraded
in performance generally, or if the relative performance of the
options has changed (perhaps even depending on the system that I use).)


With the "right" options, mplayer looks a lot better than ogle and
plays reasonably well on an 800MHz Athlon (I've never tried on
anything slower).  Unlike ogle, however, mplayer requires much more
coddling; e.g., it is not all that uncommon to find that mplayer
doesn't know where to find the "normal" audio tracks.

IMHO, it's a bit sad that the mplayer people seem to combine better
technical ability with truly poor user-interface support.  (I think
it's fine to be able to control all of the aspects, but sensible,
adaptive defaults and useful information would be a Good Idea.)


Here are some of the mplayer options that I currently use:

  -alang en -framedrop -double -ao oss -zoom

(I currently don't use the "-vo" option, but in the past have found
*some* satisfaction from "-vo x11".)

-- 
  "I probably don't know what I'm talking about."  http://www.olib.org/~rkr/