@Arachnotron, regarding that WSS line:
I read in
this PALplus document (section 5.0) that a WSS line can also flag the format as
Letterbox 16:9 Center. I was wondering if such a line can be inserted into a letterboxed MPEG-2 file to make a TV zoom in automatically when you play a letterboxed (not anamorphic) DVD.
This question doesn't really belong in this thread but I think the answer will be short:
No, it's impossible.