Weird DTA compressed file in Mafia

[teusma]

Originally Posted by FitGirl

LZMA is a solid compressor. MSC_tak operates on chunk level. So you have lots of smaller PCM chunks which are compressed individually, so later LZMA can't do much, too heavy entropy.

As for "why lzma does better on encrypted data" - it just may happen that default ordering bytes (l/b/p options for LZMA compressor) are good for this particular set of data. afair it's 3-0-2 by default. You could try to change those too in brute force and see if it will make compression better.

Try cls-razor on original and decrypted/unpacked data, it's better suited for raw-like data. lolz also may help on some raw-like stuff, but not on all.

The tests I did were applying srep first, on the files (from the sounds folder) extracted from A0.dta - 7z seems to "not like this" and then it ends up with an even "crazier" ratio of 70% vs 45% when compressing the sounds folder (from the A0.dta file) without going through srep...

But even without going through srep, compressing the original A0.dta file vs the extracted ones saves 87 MB!

By the way, if you're going to make a new repack of GTA IV, try using bzip3 (on the sound files) instead of bcm - it achieves a higher ratio than bcm does. On the file from The Godfather the Game (classic) "mx_gf_01.mus" it also stands out better than all of them (with a block size of 134 MB), except nanozip -cc. in the GUN game (audio files) it also compresses better (applying srepm3f+bzip3 to the .wad files separately

bgip3 has proven to be a good compressor, standing out more than lolz, razor, lzma, rzm in certain types of data such as unknown generic sound files.

[teusma]

when doing more compression tests with A0.dta...
A0.dta >>> 7z(lzma2) 343 MB
A0.dta >>> lolz_tt16 335 MB
A0.dta >>> razor 334 MB
A0.dta >>> bzip3 324 MB

in the extracted files
A0.dta(sounds) >>> 7z(store)+bzip3 582 MB
A0.dta(sounds) >>> 7z(store)+razor 574 MB

[teusma]

it will be? which is specific to this wav sound data from the game mafia or if you use this same encryption and compression in other PCM wav audios from others games and then compress it with a good compressor like lzma, lolz, bzip3, razor... maybe it could work... now the question is who will be the brilliant mind that will be able to do such a feat??? waiting for anyone who wants to volunteer to do this hahahaha.

um bom site pra quem quiser começar é esse:https://progamercity.net/ghack-tut/4...algorithm.html)