script to extract the .PAC asset bundle format, present in (at least) magic the gathering for dreamcast. it also converts the PVRT textures to PNGs

#usage:

install tcl and imagemagick. in particular, make sure convert is present in $PATH. if you're on a unix, installing tcl should be trivial. on windows, it is available in a package called "magicsplat". YMMV.

to run it, open a terminal and enter

$ ./unpac.tcl ./path/to/bundle.pac ./path/to/output/

this may take a while for a PAC with large images, as the PVRT->PNG decoder is largely implemented in tcl. optimization patches welcome.

this will output a directory structure like:

./path/to/output/
    xxxx.pvr - decompressed powervr texture image
    xxxx.png - for each .pvr, a matching .png is created.

    xxxx.njcm - ninja chunk model, raw 3d model data

    xxxx.njtl - ninja texlist, texture mapping info for a model

    xxxx.nmdm - ninja motion, animation

    xxxx.bin - unknown decompressed record type
    xxxx.rec - unknown record type

the PVRT converter is incomplete, and only supports the pixel/data modes present in magic the gathering. an unsupported PVRT will not be converted, but you can apply an external tool to it if need be.

#details:

.PAC is a pretty simple bundle format. it consists of a header, and a set of concatenated records, where each record begins with a 4-byte prefix specifying its type. it is a little-endian format.

Header Format (all values are 4 bytes):

         +----------------+
 0x00    | "PAC\0" magic  |
         +----------------+
 0x04    |  # of records  |
         +----------------+
 0x08    | data start pos |
         +----------------+
 0x0c    |  record 1 end  |
 0x10    |  record 2 end  |
         |      ...       |
 0x??    |  record # end  |
         +----------------+

the first record is data start bytes into the file, from the absolute beginning. it ends at record 1 end, and record 2 starts immediately after. the last entry in the record end table is the length of the file.

4 record types are known:

• NZIP, rest of record is deflate compressed data
• NJCM, ninja chunk model
• NJTL, ninja texlist
• NMDM, ninja motion

NZIP appears to be for storing PVRT images. the other types are well-known dreamcast sdk formats

#license:

if you pinky swear not to sue me for anything I pinky swear not to sue you for anything. not like I have lawyer money, anyway