[MEncoder-users] adding black bars to maintain aspect ratio

[Jon Drukman]

i am trying to figure out how to get mencoder to always output a 4:3 
image, but with black bars added to preserve the original aspect ratio 
of the input video file.  is it possible?  i've played around with dsize 
and dscale using the negative value options but i always get a stretched 
4:3 image.  i could be putting in any aspect ratio video but i always 
want a 4:3 result with added black bars (if necessary).

-jsd-