Up until now, the 64-bit packages actually had a 32-bit mplayer. Now that I have 64-bit mplayer builds, those will be included in the 64-bit packages from r5494 on. The binary codecs from
http://www.mplayerhq.hu/MPlayer/releases/codecs/ will not work with the 64-bit mplayer. Those codecs are going on 6 years old and probably have been implemented natively in mplayer already, if not and you really need them, then use 32-bit smplayer or configure 64-bit smplayer to use a 32-bit mplayer.