[MPlayer-users] stream copying making files smaller

[Chris Phillips]

not particuarly mplayer based but can someone tell me why when i use 
mencoder to copy both audio and video streams of an existing and complete 
avi movie i can sometimes reduce the file size by 10Mb or so? i'm not 
reencoding anything, so where has this space come back from? both files 
are properly interlaced, anmd i can't think of anything else that could 
affect it.. but then that's why i'm askign you guys. thanks

chris