mplayer works best with the real time clock (rtc) device /dev/rtc. It also wants to be able to set frequency up to 1024 as a user.
First make sure the rtc module is loaded - one way is to add rtc to /etc/modules
Now - lots of places I see the recommendation to add
echo 1024 > /proc/sys/dev/rtc/max-user-freq
to your startup scripts. I've never been sure where to hack this in - and the people who are giving the advice have many different suggestions. The whole thing feels like a bad hack.
So - after some investigation - I feel that it is much better to use sysctl - by adding the following to /etc/sysctl.conf
dev.rtc.max-user-freq = 1024
You can check if it worked after boot by looking inside the file /proc/sys/dev/rtc/max-user-freq - mine contains the value 1024 :)