Hi. I experienced this strange thing and I wished to kow more about it.
Let's suppose I start with a X x Y AVI file which I wat to convert to SVCD.

If I use this script:

# script to load a X x Y AVI file which
# must be converted to a 480x576 MPV
AviSource(Movie.avi)
LanczosResize(448,Y)
AddBorders(16,b,16,b)
#it must be b = (576-Y)/2
ConvertToYUY2()

the output movie video is a perfect 480x576 video with proportions kept!

Please that I tested this with the following resolutions: 720x576, 720x384, 576x320 and 608x344.

Can someone tell me why?
Eevrywhere I read about 'keepin aspect ratios' but this seems necessary only in some case (for instance, if I load a DVD using a D2V, I necessary need to put 16:9 pixels (e.g. 640x360) or I don't get anything from CCE)