Originally Posted by RoyBoy
./configure --enable-xvmc --with-xvmclib=XvMCNVIDIA
I use --enable-xvmc on its own, and I let it find the XvMC abstraction library, and I configure that to use XvMCNVIDIA (/etc/X11/XvMCConfig contains "libXvMCNVIDIA.so.1"). That means it won't show up in ldd... but if you use a commandline that forces xvmc and ffmpeg12mc then it just fails until you have things set up correctly, so it's safe to assume it's working.
If you really want to check, then try 'lsof | grep mplayer' while mplayer is running.