add subtitle into mp4

[xShrimp]

Here the scenario: (hypothetically ofcourse :D)
I have a h264 encoded video in mp4 format, and I also have subtitles (.ass) how to i place it into the mp4 as a softsub WITHOUT needing to reencode the video?

So h264 mp4 video + softsub .ass = h264 mp4 w/ optional subs

possible??

[xShrimp]

Im gonna relaborate: is it possible to add softsubs to mp4?

[bond]

its possible to add soft subtitles to .mp4. this can for example be done with mp4box

mp4box tough doesnt support .ass as input, so you need to
1) convert .ass to .srt
2) convert .srt to .ttxt with mp4box
3) edit the .ttxt by hand to include all the funky stuff like colors or whatever funky stuff was in your source .ass
4) mux the .ttxt to .mp4 with mp4box

if you dont care about colors aso you can also mux the srt directly to mp4 with mp4box