Anyone come across .m compressed rom files before?

[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:



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



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.

[wfeltmate]

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]

Nice one, I'll give this a go

[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]

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.



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.

[dreimer]

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.

[rwebster]

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.