I didn't realize that mp4 container could host DiVX5 (DX50) and XviD (XVID) video streams. Moreover, since they are simple profile MPEG-4 streams (MP4V-ES), upon packaging mp4creator changes id to MP4V-ES and after that encoder becomes transparent.
Quicktime could play those DX50 and XVID streams using MPEG-4 compliant decoder, alas there are some problems.
1. Since QuickTime is very picky it would play only AAC audio and will refuse MP3 that would be packaged into mp4 by default when repackaging DiVX or XviD AVI with mp4creator.
2. Sometimes (more often with XviD then DX50) it simply doesn't work with QuickTime while works no problem with mplayer who could decode mp4 container using ffmpeg, alas cannot play AAC using faad2.
3. Transcoding mp3 using faac and mplayer simply didn't work for me on Linux with faac unable to encode PCM wav complaining about “Unsupported output format”. Installing AAC plug-in for winamp (together with id3lib in system32) seems like the only working solution transcoding mp3 into aac for now.
TODO
1. Try faac and mpeg4ip tools on Windows, if works write a program that would repackage AVI to QuickTime compliant mp4 (i.e. mp4 with AAC)
2. Make faac working on Linux (download and compile) and try to transcode radiostream to be available as a podcast.