About PS2 ADPCM files...

Does anyone know an easy way to find the proper interleave values of songs?

I'm attempting to extract the music from TimeSplitters: Future Perfect, but all the songs are in /PAK/MUSICTS.PAK (a file around 1gb). I don't know how to unpack the archive, and the only way I could access the music was by scanning the file using Cube Media Player 2. I've determined that all the files are stereo, all the files are either 32.0KHz or 44.1KHz, and they all seem to have different interleave values (although all of them are probably between 25,000 and 30,000). I extracted a few songs in the form of the original data and tried to open them with ps2str to find the interleave value (this worked for me in MMX7) but ps2str doesn't recognize the files. I know they're PS2 ADPCM raw files of some kind though...