The final output aspect ratio hasn't been compromised by blindly sticking to 4:3, 16:9 & 2.35:1 aspect ratio rescaling, because 2.35:1 letterboxed laserdiscs aren't always a perfect 2.35:1 ratio.
Aside from calculating anamorphic outputs of letterbox source, you can input 4:3 source and calculate anamorphic output with black side borders for if you're creating a fully anamorphic widescreen DVD and don't want to zoom+crop the source to fit.
I added VCD/SVCD for those insisting on living in the dark ages of video ;)
If you want to use/see previous incarnations of this script:
ARCT v1.0 / ARCT v1.1