Cannot decompress partition of new LG firmware

[chros73]

Hi, all previous firmwares worked fine so far but the new 13.30.55 branch of LG C2 throws this error:

fakeroot ./epk2extract lib32-starfish-global-secured-o22-nameri.pine-23-13.30.55_prodkey_usb_V3_SECURED.epk
UnSQUASHFS file to: ./13.30.55.01-HE_DTV_W22O_AFABATPU/rootfs.pak.unsquashfs
Filesystem uses unknown compression, this is unsupported by this version
Decompressors available:
        gzip
        lzo

It extracts the rootfs.pak file but it cannot decompress it.

[throwaway96]

It probably uses zstd.

[chros73]

Thanks, it indeed does.
Installing libzstd-dev package on Debian 12.5 and enabling it in the makefile of squashfs-tools then building current squashfs-tools and running ./unsquashfs rootfs.pak solves this.
So, the squashfs part of this project needs to be updated to support zstd.

[chros73]

May I ask an unrelated question?
In the extracted rootfs, there are *.dbx files under /usr/share/pqdb/index directory that suppose to hold some default calibration data (e.g. peak brightness).
Do you know what file format that is or which application we can take a look at that data?
Thanks

[throwaway96]

No idea; sorry. If you want to reverse them, I'd start with /usr/lib/libpqdb.so.1.