I'm looking for help hacking a Metal Slug 2 MVS cart. I would like to play the game with in-game music disabled. Is someone here experienced with cart hacking who could give some pointers how to proceed?
Unfortunately I am not good at reading disassembler output, and MAME refused to load the game at all if I simply remove ROM files, leaving me unable to figure out which ROM chip contains the music. Also not sure if the ROM can simply be removed, or if some more sophisticated code replacement is required.
Well. I figured out so far that the V-ROMs 241-v1.v1 and 241-v2.v2 contain all audio sample data. It appears to be in some custom ADPCM format, which I had questionable luck decoding with "YM2610 Decoder.exe" I found, the sounds it produces are rather distorted. Some of the newer games V-ROMs are "encrypted", but mslug2 doesn't seem to be. Little luck finding any header identifiers from a hexdump either. Additionally, the M-ROM 241-m1.m1 is likely the note data containing the actual music composition, containing pointers to the sample data. Probably.
This is not very easy since I have absolutely no idea what I'm doing..
Your effort to remain what you are is what limits you.
Aight, the 241-m1.m1 ROM contains Z80 driver and as guessed, the tracker sequence code. Since I can't really read Z80 asm, I tried removing parts of the V-ROM contents but that didn't quite work out. Supposedly game music isn't as ADPCM samples, but rather produced using the YM2610 FM channels. I guess next I'll try to decrypt the M1 rom disassembly output to find the sequence parts and edit those.
But anyway, this is not very high priority, unlike drinking beer, so I'll proceed to that. Maybe someone educated can whip out his cluebat while I'm engaged in high priority activities.
Your effort to remain what you are is what limits you.
