VGZ disassembly

jgarneau · Post by **jgarneau** » Mon Jun 04, 2007 6:55 pm

I was wondering if anyone here had any experience with disassembling and editing VGZ logs. What I ultimately want to do is isolate instruments in tracks and figure out the way they are written by the sound driver. Then, I can write a VGZ file that plays that instrument at key tones so that I can sample it and control it via MIDI.

This would probably be a lot simpler also if VGMTool would let me strip unnecessary sounds from the files, but those options become grayed out when I load a file.

Unfortunately, I don't really know where to begin here. I couldn't find any tools for disassembling genesis code at eidolon's inn and the homebrew community for genesis seems to be fairly nonexistent anyways. Alternately, if you've got a better idea for how to control rad genesis sounds via MIDI, I'd like to hear them.

Maxim · Post by **Maxim** » Tue Jun 05, 2007 4:11 am

"Disassembly" is the wrong word really - VGM files are just a bunch of data logging what gets sent to the sound chip. VGMTool's "write to txt" feature supports a little bit of YM2612, but it's very incomplete. As I mentioned before on this forum, as soon as you finish that you'll be all set to copy/paste/edit it into the "strip out selected channels" function. Until that's done, you can try channel disabling in in_vgm and outputting to WAV, and hope the game you choose has the range of notes you want.

YM2612 FM sound is very similar to MIDI in that the key press duration affects the sound, so you'll have a hard time recording the whole range of possible sounds, even if you do hand-craft a VGM file to do that.

jgarneau · Post by **jgarneau** » Tue Jun 05, 2007 2:33 pm

Well, i've tried opening VGZs in vim and it's clearly not plaintext. I can't really seem to find any documentation of how exactly the format works. What kind of program/tools do i need here?

Maxim · Post by **Maxim** » Fri Jun 08, 2007 10:26 am

Either:
- get VGMTool, drag/drop a VGM, click on "write to text" and notice that the result is a bit incomplete, or
- get the format spec and whatever docs you can find on the chips' data formats* and try to do it all yourself.

The VGMTool support wouldn't be too hard to fix up if I knew a bit more about it; it involves maintaining a chip "state" while reading the data in and echoing the useful results to a file. That YM2612 doc was my attempt to get going on that a few years back, but the combination of it being really quite complicated and me not having time conspired to squash that. If you code something, I'd be happy to incorporate it.

* seems slightly screwed up by some bad charset conversions, I'll have to see if I can fix it sometime.

jgarneau · Post by **jgarneau** » Tue Jun 12, 2007 1:30 pm

thanks! i'll see what i can do with this.

CMA Death Adder · Post by **CMA Death Adder** » Wed Jun 13, 2007 3:39 am

jgarneau wrote:the homebrew community for genesis seems to be fairly nonexistent anyways.

Well now that's just not true. You only need to know where to look...

Siamey · Post by **Siamey** » Thu Jun 14, 2007 5:02 am

Death Adder! Im a big fan of your work on zophar! good to see you!

Umm ive been trying to make a sample set of all the sounds in sonic 3 (and knuckles maybe too) and ive been listening to the gyms and just muting channels and exporting them through winamp them chopping them up in recycle.

Something interesting ive realized though, the GO sound from launch base zone... is actually in my yamaha keyboard (dgx202) but in high quality, maybe ill go back and check what other samples are in there that i recognize from genesis soundtracks.

Also, i have about 13 genesis in my closet (wide array of models except no majesco) and im wondering if theres any way to take the ym2612 chip out (or leave it in) and some how make a synth that i can control with my midi keyboard. or something crazy like that.

also im thinkin... isnt there any tools for writing gym songs like this dude was asking about? is my understanding correct that gyms are just notes and stuff and the winamp plugin (that i use for example) is the chip emulator? also, sorry if i use gym and vgm interchangably, ive only used gyms and dont really know the difference.

by the way (sorry for all these questions at once) when im listening to like "hydro city zone act 1" the drums and instruments will randomly switch from regular to shuffled (like swing) is that supposed to be like that? i cant see them writing the song like that...
maybe this is a problem with the ym chip or my plugin? or maybe the gym format not being stable or precise? augh so many questions!

anyways, im glad ive found this place, im a huge fan of genesis soundtracks.
YAY!

Siamey · Post by **Siamey** » Thu Jun 14, 2007 5:13 am

holy crap! the wondermega/Xeye had midi capability?! does anyone know much about this? i want to buy one and use it as a synth in my studio!

Kaminari · Post by **Kaminari** » Thu Jun 14, 2007 10:35 am

CMA Death Adder wrote:Well now that's just not true. You only need to know where to look...

Not sure if you're referring to Beggar Prince, but I'll go on and say that this game is by no means homebrew -- it's actually ten years old already, and the people that make it pass for a brand new release are misleading at best. Btw, was the original Taiwanese company ever consulted about this commercial translation?

neologix · Post by **neologix** » Mon Jun 18, 2007 6:15 pm

VGZ is a gzipped vgm file, renamed from originalfilename.vgm.gz to originalfilename.vgz for convenience i guess. i currently have a win32 command-line tool YMstat (search the forums for YMstat) that will disassemble a .GYM log (i've been modifying it on my personal comp to handle .VGM as well and the next release will probably be called VGMstat and have win AND mac gui versions). you need to decompress a .VGZ before you can even hope to VGM disassemble it. if you're not hard up for a win gui version of my tool, i suggest waiting until i release VGMstat, otherwise VGMtool sounds like it'll be enough for now (simply cross-reference its ym2612 output w/the VERY informative ym2612 docs linked earlier found on maxim's site).