I am currently trying to create subtitles for some proprietary Sony software. Unfortunatly, it only recognizes Sony's own .m4t subtitles format. After some research I found that this subtitles is also used in Crackle app for PS3.
There is source code of this app available here: https://github.com/eigentopia/PS/tree/92d04b264016c4a16c6772bd9cf7c1184649cf54/js/app/com/dadc/lithium
Look for model/TTMLSubtitleModel.js
This format appears to be some variant of TTML subtitles.
Subtitles converted to .ttml and with extintion changed to .m4t is recognized by the programm, but isn't displayed.
Any help with figuring out this format (or it's differences from standard TTML) is appreciated.