NAB is nominal analogue blanking. It means that eight pixels on the left and eight pixels on the right (for NTSC) are junk and do not count toward the calculation of the aspect ratio. They can be discarded.

I do not want an anamorphic mkv, because the player will do a better job of resizing this than the filter. It would be like playing an AVI on a PS3: It would be scaled up, no problem. :-)

I have been playing with deleting the anamorphic resizing section of the script and replacing the cropping line with:

Crop(8,96,-8,-96,align=true)

When I do this, the vertical resolution ends up doubled though... :-(