prerendered subtitles on MP4 or MJPEG-AVI

[pokerpoker]

hey, i'm working on UMD and PSP video formats, after many weeks of research, i have learnt that UMD's subtitle format isn't known by anyone on the internet.

i'm trying to make MP4 files with optional subtitles, i'll use them on the PSP.
i tried TTXT subs but PSP doesn't recognize them.

looks like i need prerendered subtitles (probably same as UMD) for it to work, the internet is full of hard-subbing and sub-ripping info but it's kinda difficult to do backwards (except in DVDs)

i mailed Sony to learn their subtitle format but they didnt give me that info. i asked example video, no luck.
i have access to Sony's UMD movie making tools but it only accepts .sst and .nav files, which aren't known by anyone too.

in short, i'm trying to add prerendered optional subtitles to a MP4 container. i heard that PNG subtitles would work.
thanks for any help.

btw i tried Nero's Recode2 and advanced content too, ok on pc but not supported by PSP

edit:
looks like i can use MJPEG videos too. i can mux text-based subs in it but i need image subs (idx/sub most likely)
when AVI contains divx it's easy but noone likes mjpeg

[poisondeathray]

I think you can use a psp mod to play srt soft subs

search for pmp mod

http://www.fx-world.org/wordpress/?cat=2

[pokerpoker]

I think you can use a psp mod to play srt soft subs

search for pmp mod

http://www.fx-world.org/wordpress/?cat=2

i know about that homebrew (btw my psp is modded), it often has subtitle positioning problems

i didn't mean to make this post about psp, it's about subtitles