[MPlayer-users] what are b frames?

[christopher j bottaro]

couldn't find much about em in the documentation or the man pages...where can 
i go for info about em?  what do they have to do with going from dvd to divx?  
pros, cons, etc...?  i think i read something about they make encoding more 
efficient (does that mean faster?) and that they can improve the quaility of 
high motion/action scenes...

thanks for the help,
-- christopher