Perhaps as an alternative to my earlier question, I maybe able to extract the subtitle from the MP4. Does anyone know how this may be done?

My research shows a product for Windows that claims to do such a thing and mencoder should also - but I've not successfully create either SUB/IDX nor SRT files using mencoder
{something like this to create SUB/IDX files does create the files but the SUB don't work}:

Code:
 mencoder videofile.mp4 -nosound -ovc frameno -o /dev/null -slang yourlanguage -vobsubout outputfilename
-- da Lizard