afd for dvb aspect ratio

How easy is it to support AFD in mplayer/mencoder? This is basically
a bit in the mpeg header which is broadcast to indicate which area
in the picture actually contains the content.
Most DVB broadcasts are widescreen and use black bars to show
4:3 content - and the AFD data is used to indicate that the decoder
can discard the sides. This is documented here:

http://www.dtg.org.uk/publications/books/afd.pdf

Any possibility for support in mplayer/mencoder? Currently it's
difficult to automate recording and encoding of DVB broadcasts with
correct cropping, but this would help a lot.

Thanks,
Ben