[MPlayer-users] setting aspect after encoding

[j.a.l]

while encoding i screewed up, setting aspect=1.33 instead of 1.78.
is there a way to set the correct aspect ( perhaps by direct write on 
.avi offset ) but encoding it again ?????? ;
( using the -bad - avi as source and huge vbitrate doesn't really speed 
up the process of re-encoding )