Anyone come across .m compressed rom files before?

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rwebster
Posts: 25
Joined: 01 Mar 2021 18:15

Anyone come across .m compressed rom files before?

Post by rwebster »

Hey folks. Just getting into archiving and extracting ROMs (digital releases, disc compilations etc). I've extracted Sega Vintage collection files from my Xbox 360, and the files are all in what appear to be compressed and/or encrypted formats that basically don't show up anywhere online. I've asked on Reddit for help, but nobody knows yet.

The files have a .m extension, and when viewed in a HEX editor the first lines all start with mxb...

Here's the file list I've got:

Image

And here's the first line in a hex editor:

Image

I would link to my Reddit thread, but it links to the single forum thread I found discussing it, which includes a download of the files. Not sure if that's ok here.

I would very much like to extract the ROMs from these, for archival purposes and to check the hash data against existing dumps.

Here's a link to the details of this particular collection: https://segaretro.org/Sega_Vintage_Coll ... dd_%26_Co.
Last edited by rwebster on 07 Mar 2021 12:25, edited 2 times in total.
wfeltmate
Posts: 22
Joined: 18 Feb 2021 17:31

Re: Anyone come across .m compressed rom files before?

Post by wfeltmate »

Dreimer is likely pointing you in the right direction. Proper Alex roms should be about 131KB in size, but yours are only 76KB. This fits well with the only mentions I could find of .m Sega roms having been compressed using mdftools.
rwebster
Posts: 25
Joined: 01 Mar 2021 18:15

Re: Anyone come across .m compressed rom files before?

Post by rwebster »

Nice one, I'll give this a go :)
rwebster
Posts: 25
Joined: 01 Mar 2021 18:15

Re: Anyone come across .m compressed rom files before?

Post by rwebster »

No luck with mdfDecompressor.exe unfortunately. No output in the command window, and nothing extracted.

I dumped my Sonic the Hedgehog Game Gear ROM from my 3DS as I remembered that uses mdfDecompressor.exe, and the header is different to these Sega Vintage ones. Just to make sure the program works I ran it on my Game Gear ROM and it extracted fine.

My SVC ROMs have mxb in the header, not mdf, so the program isn't doing anything with it. Just for fun I copied over the mdf header from game gear to replace the mxb header in my ROM, but no luck. Unhandled exception.
rwebster
Posts: 25
Joined: 01 Mar 2021 18:15

Re: Anyone come across .m compressed rom files before?

Post by rwebster »

I've extracted the whole package again, rather than just the roms, using wxPirs, and every file except for default.xex (xbox app file), images, and some sound files, is a .m file with mxb in the header.

Image

I wonder if this is something with MS or Xbox data specifically (although that would surely show up in searches), or if the decompressor for all these files is buried inside the default.xex file.
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dreimer
Posts: 147
Joined: 14 Nov 2015 13:26

Re: Anyone come across .m compressed rom files before?

Post by dreimer »

rwebster
Posts: 25
Joined: 01 Mar 2021 18:15

Re: Anyone come across .m compressed rom files before?

Post by rwebster »

dreimer wrote: 07 Mar 2021 15:54 Only tool left in my collection...
https://github.com/farmerbb/RED-Project ... Collection
https://github.com/farmerbb/RED-Project ... Collection
https://github.com/farmerbb/RED-Project ... m-Archives
https://github.com/farmerbb/RED-Project ... nesis-Mini

All tinkering with alldata.psb.m files, but maybe one of the parameters does the job you want it to.
Thanks mate. I've actually reached out to the owner of that project, since I'm contributing in other ways as well. I have a feeling the MArchiveBatchTool might be able to decompress the files, since it is used on other .m files create by M2 (as you've shown, they did Castlevania Collection for example). It's just figuring out the right method and seed etc.
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