I saw
NT*3 somewhere before...
*thinks* Right!
Eternal Sonata features
NTX3 files in the XBOX 360 demo
(Probably the 'X' is for XBOX and the 'P' for Playstation),
they also have the same structure.
But there was something else...
*thinks* ah....,
.nut files! I remember them from
Tales of Symphonia (PS2 version)! They had
TIM2 instead of
NT*3
(funny thing I was currently working on them anyways

)
All of them
(ES,ToS and those files) have the same structure
(eXt and GIDX readable in the first few bytes)
I will start tomorrow to write a generic .nut converter
(will take 2-3 weeks I'm slow
) with a GUI
because this seems useful for multiple games and the format seems pretty straightforward.
Alternatively if you just want a few files converted I can do it by hand
(slapping a custom DDS header on them)
Edit after reading linked topic above:
Maybe just changing the
endianess in the script to
little could do the trick, PS3 is little endian if I remember correct
(didn't test it)