[MPlayer-users] variable bitrate? among other encoding questions

[christopher j bottaro]

hello,
i'm learning how to convert a dvd to divx using mencoder and the 3 pass 
method.  the documentation says to execute the following command for the 
first pass to make the audio only file:

encoder <file/DVD> -ovc frameno -oac mp3lame -lameopts vbr=3 -o frameno.avi

now i have 2 questions.  what is the difference between the vbr methods?  0-4 
correspond to cbr, mt, rh (default), abr, mtrh.  where can i find info about 
each one?  which one is the best?
second question:  i know i can increase the volume by using the lameopt 
vol=10, but is there anyway to "normalize" the volume?  something like 
vol=norm?

now for the other 2 passes:
mencoder <file/DVD> -oac copy -ovc lavc -lavcopts 
vcodec=mpeg4:vpass=1:vbitrate=<bitrate>
mencoder <file/DVD> -oac copy -ovc lavc -lavcopts 
vcodec=mpeg4:vpass=2:vbitrate=<bitrate>

for these two passes, i want to scale the movie down to 640xhhh keeping the 
aspect ratio.  i know i can do this by using '-vop scale -zoom -xy 640'.  now 
my question is should i use those options in both passes 2 and 3?  or in just 
pass 2 or just pass 3?  also, it says in the documentation that scaling is 
bad.  why is it bad?  will the resulting divx be able to be played in other 
players?  i.e. win media player?

thank you for the help,
christopher