FAVC and Aspect Ratio

[sambat]

I was converting an AVI clip to DVD format using FAVC and was wondering why D1 and Half D1 result in different ARs.

Source avi file is 576x320.
Selecting resolution Full-D1 results in a 16:9 movie.
Selecting resolution Half-D1 results in a 4:3 (letterboxed) movie.

[manono]

Because only Full-D1 supports 16:9. If Half-D1, it has to be 4:3.

[sambat]

Much obliged - thank you.