The VideoLAN Forums

I have uploaded a sample file here: streams.videolan.org/incoming/MP4_with_ttxtSUB

I get this message from VLC:

main error: no suitable decoder module for fourcc `tx3g'.
VLC probably does not support this sound or video format.

for me videolan (one of the latest nightly builds) doesnt show an error when i try to play .mp4 files with mpeg-4 part17 subs (as you pointed to), but it simply doesnt display the text (altough the subs are choosable in the vlc menu)

afaik fen once worked on implementing mpeg-4 timed text to vlc but never really finished it, i assume thats the reason why it doesnt work correctly atm

btw you can create your own ttxt mp4 files with the mp4box from the gpac project (which can be found on sourceforge, together with some docs)