Reverse Engineering Asobo Custom LZ Variant With Multiple Known Past Versions

[EmilyWasAway]

I'm reverse engineering a version of Asobo Studio's DPC archive format used in the PC release of the game FUEL (2009). I am able to unwrap the first "layer" of the format by breaking the archive down into the files described in the DPC header using a modified version of this MexScript. However these extracted files appear to be compressed with a custom LZ variant. Some games released before FUEL (CT Special Forces: Fire for effect, Ratatouille, and Wall-E) each used a slightly different LZ variant than the previous release so I am expecting FUEL to use something similar to those. @Shelwien has provided a series of unLZ_rhys scripts in previous posts (linked at the bottom) but none of them seam to properly decompress the files I extracted. I have attached a selection of extracted files that appear to be compressed and contain a small amount of text near the beginning. They all follow a similar pattern to the one in this image:



Which closely resembles the compressed files from the previous posts.

In theory this should only require a small modification to the unLZ_rhys tool but unfortunately I cannot seem to figure out the header layout/mask for this new version of the format. Any help with how to modify the tool or advice in general would be greatly appreciated. If you need more samples or the original DPC files I can provide them.

https://encode.su/threads/3147-Rever...tom-LZ-Variant
https://encode.su/threads/3526-Asobo...ta-Compression

[Dresdenboy]

With those runs of zeroes and the compression ratio in the samples zip I think those files aren't compressed at all, just some custom data format.

[EmilyWasAway]

I considered that it could be a custom format but the similarities to the previous DPC formats and sections of the file that look like this



lead me to investigate the possibility of compression. Although if it is compressed, it's not by much.

[Shelwien]

Its not a compressed format (at least not in the first layer of structure), but just a structured format with length prefixes
and mostly floats inside.

seg000:00000000                 dd 3Fh

seg000:00000004                 dd 4

seg000:00000008                 dq 3Bh

seg000:00000010                 dd 52F79F96h

seg000:00000014                 dd 0C939BCA1h

seg000:00000018                 dd 0D24B3F6Fh

seg000:0000001C aVLinkLefthandM dd 55

seg000:0000001C                 db 'V:LINK "LeftHand" "MUSCLE_OFF_1_SUSPFL4_LOD1" AxeZ LOD1'

seg000:00000057                 dd 0A6h

seg000:0000005B                 dd 62h

seg000:0000005F                 dq 44h

seg000:00000067                 dd 73DC6A13h

seg000:0000006B                 dd 0A3F0FCD9h

seg000:0000006F                 dd 4AB1A4C3h

seg000:00000073                 dd 681AF697h

seg000:00000077                 dd 0BE02FCF1h

seg000:0000007B                 dd 0BE5A0EC8h

seg000:0000007F                 dd 0BA5BF080h

seg000:00000083                 dd 3E801E69h

seg000:00000087                 dd 3F800000h

seg000:0000008B                 dd 0

seg000:0000008F                 dd 0

seg000:00000093                 dd 0BE02FCF1h

seg000:00000097                 dd 0

seg000:0000009B                 dd 3F800000h

seg000:0000009F                 dd 0

seg000:000000A3                 dd 0BE5A0EC8h

seg000:000000A7                 dd 0

seg000:000000AB                 dd 0

seg000:000000AF                 dd 3F800000h

seg000:000000B3                 dd 0BA5BF080h

seg000:000000B7                 dd 3E801E69h

seg000:000000BB                 dd 3E801E69h

seg000:000000BF                 dd 3E801E69h

seg000:000000C3                 dd 3EDDE882h

seg000:000000C7                 dd 0

[EmilyWasAway]

After reviewing what you both have said it makes sense that the samples I posted are not using compression at this layer of the format. I'm not certain but these files extracted from the header of the DPC appear to reference data located further down in the DPC but the headers themselves are not compressed in this version. Thank you for the help.

[Dresdenboy]

After reviewing what you both have said it makes sense that the samples I posted are not using compression at this layer of the format. I'm not certain but these files extracted from the header of the DPC appear to reference data located further down in the DPC but the headers themselves are not compressed in this version. Thank you for the help.

You're welcome!

Most of the files are compressed at a compression ratio of ~2 to 5. in this ZIP. FONTES_*, MENU_* and TELEPORT_* are less compressed, with the latter two containing a lot of 16 bit data. They might contain bitmaps.