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 Post subject: VGM Logging Help
PostPosted: 2021-09-23, 9:56:43 
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Joined: 2019-04-08, 0:58:43
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Hi, I'm new to VGM logging and wondered if I could get some advice.

I've installed the MAME VGM mod and edited mame.ini to write VGMs. Works great and so simple to use. :)

I've only tested one game so far, Jumping Jack by Universal, but I've noticed something unexpected. When I listen back to just the channel playing the JJ melody it periodically drops out and is replaced with sound effects and the missing short sections of melody appear on a different channel. The same is true for the bass line. Is there a way to stop music criss-crossing channels or is this hardware accurate?

Also I tried exploring Service Mode in case there was a sound test which played music but after many attempts I couldn't get Service Mode to trigger. Pressing TAB did bring up some dip switch settings so maybe this is Service Mode?

Any advice on ripping music from mame games appreciated.

Thanks.


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 Post subject:
PostPosted: 2021-09-23, 16:24:57 

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If I have to guess, it's probably due to how the game handles the sound. There are certain arcade games that have multiple of the same chips, but the VGM format only supports up to two each for certain chips. So, some of the music is handled on the third and/or fourth chips which is why you don't hear some of the music and you get sound effects instead.


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 Post subject:
PostPosted: 2021-09-23, 18:00:46 
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Jumping Jack uses four SN76489A chips so you may be onto something @BoxCubed although MAME actually outputs two VGM files (two chips per file) so the output from all four chips does appear to be being captured.

The puzzling bit for me is still why, for very brief intervals, music switches channels and back again (I'm thinking it might be occurring when a certain sound effect triggers such as the player knocking a monkey off a see-saw). With twelve tone and four noise channels available to the game's programmers I would expect there to be dedicated channels for music and effects.

Of course the VGMs may be fine and WinAmp could be importing them incorrectly?


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 Post subject:
PostPosted: 2021-09-23, 20:44:54 

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Actually, having many channels of the same type is the point where dynamic channel allocation begins to get useful.
So it would make sense that the assignment between internal "music channel" and "sound chip channel" can change depending on what is free.

Although I haven't seen that with PSG chips yet (except for GEMS on the MegaDrive), just using the next free channel is very common with MIDI-based formats. (XMI/MID playback OPL, Sega System 32 and Model 2 sound formats)


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 Post subject:
PostPosted: 2021-09-23, 23:29:01 
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I completely agree however what I'm hearing is data from two or more active channels being jumbled up mid song if that makes sense.

It might be that Jumping Jack's sound configuraton confuses the VGM exporter or the VGM plugin for WinAmp isn't loading the data correctly.


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 Post subject:
PostPosted: 2021-09-24, 0:56:45 

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I doubt it's an issue in the VGM logger. If it was, I think it would affect a lot of other games, for example all games that used multiple AY chips. I logged music from Gyruss (5x AY-3-8910) and had no issues. (Though I used an earlier version of MAME with the VGM mod that I modified for the DAC logging).

Issues in the VGM player plugin would typically result in completely broken sound. Not just tracks jumping around between channels (which imo, sounds a lot more like a sound driver quirk in the original game).


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 Post subject:
PostPosted: 2021-09-24, 8:51:19 
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Fair enough. :)

When you guys are logging VGM from MAME is it usual to sit and play the game or is there a smarter way to do it, using a manufacturer's test mode or something?


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 Post subject:
PostPosted: 2021-09-25, 13:56:04 

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When possible, we use the sound test from the "Service Mode" that you can activate most Arcade games.
Not all games have a sound test though and some don't let you listen to songs in full.
In such cases, we develop small hacks that lets us log the songs without playing through the game. If you need help with such things, you can just ask in the chat.


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 Post subject:
PostPosted: 2021-09-27, 9:41:03 
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Thanks for the info @ValleyBell.

Still trying to figure out how to access MAME VGM service mode. Pressing F2 once followed by F3 to reset the game doesn't work for me.


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 Post subject:
PostPosted: 2021-09-27, 14:37:55 

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Not all games have a service mode. If the following don't work, then it's very likely that there is no service mode

- press tab to bring up the MAME OSD, go to DIP switches and toggle the option called "Service Mode", "Diagnostics" or similar
- press F2 as mentioned
- holding F2
- press F3 (reset) while holding F2
- holding 9 (service credit)

Some IREM games require you to press both start buttons after the "ROM OK/RAM OK" screen (when the service DIP switch is on, it will otherwise be stuck on that screen)


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 Post subject:
PostPosted: 2021-09-27, 18:46:56 

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Wow, I didn't know that Irem games have a Service Mode, but hidden (at first sight when I activated it in switch, it just stayed in RAM OK/ROM OK, and did nothing), and that lets you see the sound, but not in a good way, just put the mode and the music plays, and you can not stop it, and when you change it plays quickly, and there are some soundtracks that I would be interested in doing as Fire Barrel (Air Assault), Armed Police Unit Gallop (Cosmic Cop), and make them in MAME.


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 Post subject:
PostPosted: 2021-09-29, 13:03:24 
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I can see it's necessary to treat each machine on a case by case basis.

I did manage to access service mode on one game (maybe Bubble Bobble) but not others. Once in service mode I was left staring at a grid pattern. Tried hitting different keys but couldn't figure out how to navigate.

Not sure I'm knowledgable enough for this kind of thing but I appreciate the advice. :)


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