After much trial and error, I believe I've found the best way to encode TED Talks videos for viewing on my Nokia N73. The TED videos that you can download off their site are H.264 video + AAC audio in an MP4 container and hence, should be playable directly with the pre-installed Realplayer on the N73 since Nokia claims H.264/AVC compatibility for this phone. However, things never quite work out so easily, do they? At least not for me. I've never been able to get Realplayer to play these videos. Plus, the Realplayer on N73 sucks. The less I have to use it (i.e. never), the happier I'll be.
$ ffmpeg -i ted_video.mov -f avi -vtag DX50 -vcodec mpeg4 -r 15 -acodec mp3 -vol 600 ted_video.avi
vtag is needed to tell DivX player that "this is a bonafide DivX file so please go ahead and play it without worrying that you'll trip and fall and lose some of your bits trying to play a non-divx video." I chose a framerate of 15 fps so that the poor 200MHz ARM processor can keep up. Finally, the
vol switch pumps up the volume so that I can listen to the video clearly out in the crowds, in the subway and (more importantly) over the inane programming shown on TV Mobile.
Hope this info will be of some use to someone somewhere.