I spent a little while trying to figure this out, apparently the -r argument is significant:
ffmpeg -i superman_the_mechanical_monsters.mpeg \ -title "Superman: The Mechanical Monsters" \ -s 320x240 -b 512 -ar 24000 -ab 64 -r 29.970030 -f psp M4V12345.MP4
The -title seemed fubarred, but the rest seems to work. I’ll refine this more later.
Filenames apparently need to be of the form M4VXXXXX.MP4, where the X’s are digits.