Doom Eternal uses two libraries on this file however I'm not sure if this applies to the whole game.
oo2core_7_win64.dll ->
283 MB > 421 MB (691/1332)
oo2core_8_win64.dll ->
283 MB > 479 MB (790/1332)
For some reasons, streams that can be processed 7 cannot be processed by 8 and visa versa.
However if you precompress the game using both libraries one after the other you get
283 MB > 421 MB > 614 MB
The second pass using oo2core_8_win64.dll processed the remaining streams (640/640).
This is part of the reason I added --oodle= parameter in xtool, to allow you to specify exactly what library you want to use.
Code:
[External compressor:doom7]
header = 0
packcmd = xtool.exe precomp -mkraken,l6,n256 -c32mb -t50p --oodle=oo2core_7_win64.dll - - <stdin> <stdout>
unpackcmd = xtool.exe decode -t100p --oodle=oo2core_7_win64.dll - - <stdin> <stdout>
[External compressor:doom8]
header = 0
packcmd = xtool.exe precomp -mkraken,l6,n256 -c32mb -t50p --oodle=oo2core_8_win64.dll - - <stdin> <stdout>
unpackcmd = xtool.exe decode -t100p --oodle=oo2core_8_win64.dll - - <stdin> <stdout>
Your arc.ini then looks like this then you run the method
-mdoom7+doom8