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Are there any coders who could have a look at this? http://xboxdevwiki.net/XDVDFS#Random_blocks

https://github.com/JayFoxRox/xbox-dvd-compress

It would be great to have a tool developed similar to nNASOS for dramatically reducing the compressed size of Xbox images (by scrubbing the random padding and allowing it to be regenerated)

Jackal wrote:Are there any coders who could have a look at this? http://xboxdevwiki.net/XDVDFS#Random_blocks

It would be great to have a tool developed similar to nNASOS for dramatically reducing the compressed size of Xbox images (by scrubbing the random padding and allowing it to be regenerated)

Yeah I would like to. Is this known to be correct?

great, thanks for the link, very interesting for research
will take a look after figuring out the 3ds decryption

It works!

https://pastebin.com/vfC9GSLX

Tested it with the game from the example and known seed

Compressed size of archive 65 mb, against 6.4Gb with "garbage"

Great, Jackal, thanks for the info!

OK, test it on "Petit Copter (Japan).iso"

2 executables

1) xbox_dernd.exe - derandomizer

like "nasos deux", it doesn't change the structure of the file, just replaces "random data block" with block full of "JUNK", it is like zeroing but it serves as a mark

you will get a file called "Petit Copter (Japan).f401863e.iso"
f401863e is a seed for the random generator

2) xboxRegen.exe - regenerator of random data

replaces blocks full of "JUNK" with random data blocks, generated by using seed number


xbox_dernd is tweaked to be compatible with the Petit Copter for test purpose
the tweak is, that it bruteforces only 1/16 part of full range
from 0xf0000000 to 0xffffffff (f401863e)
to speed up the test process, it tooks about 8 seconds on my rig
brutforcing the full range will took about 8 minutes

P.S. 7zipped iso is 48,7 Mb

wow, nice work, that does work really quickly too.



That's a massive space saving.

Great work, keep on saving me a loooooot of space on my rigs!

Hi,

great job! 3 questions:

- Is there only 1 seed value for the entire disc? So it shouldn't take long to brute force every disc once they are supported?
- Does nNASOS also fill with "JUNK" pattern, or something else?
- I tried 2 random games (Crimson Skies - High Road to Revenge (USA) (En,Fr,De,Zh,Ko) + Tony Hawk's Pro Skater 2x (USA) ), but it couldn't find a seed value. So just this 1 game is supported for now?

Hello!

1) 1 seed value for entire disc, since current tool uses only one thread brutrforcing takes around 8 minutes on modern PC, I'll try to speed it up

2) I cannot tell for sure about nNASOS, if it uses the first version of NASOS, no it fills garbage blocks with zeroes and should have header block with marks which block uses garbage padding.
NASOS deux replaces garbage with "JUNK", and the image is playable in emulator
/viewtopic.php?t=13218

3) Yes, this version supporting one game only

this is time taken to brute the seed value for "Silent Hill 2 - Inner Fears (Europe) (En,Ja,Fr,De,Es,It).iso"