Have you (josephabennett), or has anyone else figured out any more on this? I too was doing some experiments with muxing text tracks in with mp4 streams using mp4box, but I couldn't come up with anything that iTunes or iPod would recognize. I took some MP4 files (actually AAC audiobooks) that had working chapters a la Apple's ChapterTool, and extracted the raw text track... the data looks a bit odd--like regular 3GP text samples, but with a "Text" sub-type on the track and some additional binary data tacked on the samples' ends--but maybe with some patches MP4Box could be persuaded to embed similar text tracks. Anyone tried this yet? Is it worth a try, or do you suppose there's something else unique going on with how the data is actually muxed, that mp4box would have a hard time emulating?...if I (or anybody else) can figure out how iMovie multiplexes chapters into the output mp4, then we just need a program that does that, and we're good. OK, let me dig into that and see what i can find.