I've used the cmp OPBB script to decompress J-Stars .pak and noticed that it only does it partially. So I tried booting up the game through RPCS3 and searching the ram for the initial decompressed part and managed to extract all the character models and texture files. And I decided to post some samples of compressed and uncompressed files, so somebody can help me figure out the correct compression to extract the rest of the files like UI, animations and skill without the need of the emulator because it almost killed my PC (sorry for my potato), and to extract the files from the PS4 version to get them in higher resolution.
I tried using comtype_scan2, but none of the results looked like the files from the ram dump.
This is a comparison of the OPBB script output and ram dump of character_model_000_i.stpk which is an archive that contains the raw mesh data for Luffy.
As you can see at offset 0x30c00 they start to differentiate with a "CH0" indicator, how do I know the ram dump is useful, well I already extracted the mesh correctly into an obj.
character_model_xxx_i.stpk is the raw mesh data, character_model_xxx_v.stpk is the raw texture data and character_model_xxx_m.stpk is the archive with the indexes.
_m and _i are extracted partially with the OPBB script, while _v outputs an error.
A comparison between the _i and _v compressed paks, see they use a different header, _i with "CL0" and _v with "CLH" and "CH0".
Here are the samples of Luffy 000, Toriko 013, Zebra 014 and Killua 018. PAK are the compressed files and STPK are the uncompressed ones. samples