I've played with a few encoders but have been surprised (and annoyed) at the lack of custom size/16:9 support (at least as far as I can figure out) in Riva, etc.
Found one very similar called TaKa http://megafonts.free.fr/flv/index2.html) that has a very easy interface to add/edit the actual command line options for custom sizes/configs.
Found one very similar called TaKa http://megafonts.free.fr/flv/index2.html) that has a very easy interface to add/edit the actual command line options for custom sizes/configs.