Help identifying a compression algorithm in Virtual Worlds

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gu3
Atarian
Atarian
Posts: 5
Joined: Fri Apr 05, 2024 6:49 am

Help identifying a compression algorithm in Virtual Worlds

Post by gu3 »

Hi,

I'm doing some research to reimplement the decompression routine from the Virtual Worlds release for AtariST (https://www.mobygames.com/game/37202/vi ... ollection/). This is currently blocking user from replaying the Freescape games in ScummVM, as you can see in this issue: https://bugs.scummvm.org/ticket/13942. There is a workaround to get the compressed files, but it is very annoying since it requires user to use the debugger: https://wiki.scummvm.org/index.php?titl ... T_releases

Any idea on how to open these PAK files?

Thanks!
czietz
Hardware Guru
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Posts: 2485
Joined: Tue May 24, 2016 6:47 pm

Re: Help identifying a compression algorithm in Virtual Worlds

Post by czietz »

At least for "D.PAK", this is just a loader, a regular program (.PRG) disguised by the extension. I loads the contents of DRIL.ALL into memory and then jumps to the beginning of said memory. The decompression code is in the first 300 bytes or so of DRIL.ALL.
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