use Perl

mencoder -vf rotate=1 -o out.mpg -oac copy -ovc lavc in.mpg Untested but I'm pretty sure that's the ticket.

Yeah - it makes it pretty easy to do some cool effects. For example I hacked up the climatic final scene of $big_summer_blockbuster so it had the headlines from the BBC scrolling behind the protagonists in giant, 2 mile high letters. It is, however, a giant hack. It communicates via a named pipe and some pretty hairy escaping but it seems to work well.

I actually built a Perl/Maya bridge many, many years ago. You inspired me to go dig it out and stick it somewhere https://svn.unixbeard.net/simon/Pel-Mel/trunk/