Try mplayer as follows:

Copy from original firmware three files:
/usr/bin/mplayer
/lib/modules/*/s3c-mfc.ko
/lib/modules/*/s3c-pp.ko

run ldd /usr/bin/mplayer
See what libraries are missing, find to which packages they belong, and apt-ger install them (all are available).
After every boot insmod the two modules, make sure the device files are accessible to the user, and then you can use mplayer.

If those instructions are not enough, I'll add the details in a few days, when I get the chance to do it again.