enhance the Volume of Ac3

Hi,

I have a movie wich has AC3 Sound but its so fu.... quiet that it's realy hard to understand everything. Is there a way to enhance the loudness of the Ac3 file from the movie? I can't find an option at bsplayer so i tried nandub but then the sound gets very scary. :roll:
If you have an idea how i could get this one louder but in a good quality then plz help me. Maybe there is a "plugin" or something for bsplayer to correct the loudness?