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Neo Geo Pocket VGM sample support

Technical discussion about the VGM format, and all the software you need to handle VGM files.

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  • Knurek Offline
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  • Joined: 2011-12-30, 1:01:56

Neo Geo Pocket VGM sample support

Post by Knurek »

I've just finished Faselei! logging and while doing that I've noticed that the game has a streamed song playing during introduction.

I've tried logging it with MESS VGM mod, and it doesn't seem to be supported - logs came up empty.

Is there a chance of adding support for this type of music? I'm not really sure if it has been used in any other games, so if it's too complicated, I will just resort to wavewritting.

Post by Sonic of 8! »

This topic needs to be moved, because this section is for the problems and suggestions, but for the site only. Anyway, if I remember, NGP (and NGPC) has a DAC chip. Don't sure if the game that you was logged uses the Sample playback made by T6W28, like a SN chip.
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  • ValleyBell Offline
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Post by ValleyBell »

[topic moved]

Yes, the NGP has a custom DAC chip and it plays raw unsigned 8-bit samples.
Sonic Pocket Adventure uses it to play the Sega sound, for example.

Right now there's no way to log this and I don't know if I'll ever add generic DAC support, so you need to log WAV files. (or you extract the data from the ROM)

Post by Rotating Username »

I wish I had thought to look for this topic before I imported the Faselei rom into Audacity a dozen times.
Well, while I'm here, I have a few questions....nothing critical, of course, just trying to round out my knowledge.

It was through that trial and error that I found the song in question at 0x144100, give or take maybe 100 bytes.
The sample lasts until about 0x194500 and change, although there are two more samples after that (both explosion noises).
I have no idea how to narrow down the exact addresses, other than aforementioned trial and error.

(incidentally, while the wavewrite mp3 that Knurek settled with seems clear enough audio-wise, MESS seems to cut off the last few seconds of the song, so it's incomplete)

Now the questions....thanks to this topic (and ngp.c at MESS), I know the samples are definitely 8-bit unsigned. However, I figured out the sample rate of 8000Hz by guess and check, and I guess the endianness isn't even an issue in this case. Is there any kind of general guide to figuring out/intuiting these things when important raw data? I should probably sit down and figure these things out myself (especially endianness), but I'm always hoping for a shortcut.

Another thing - the sample seems to be monaural, but the NGP has two (?) DAC chips. Does this mean that the system achieves stereo by playing the sample on both chips simultaneously?

Finally, assuming someone bothers to extract the sample in a relatively clean manner, what would be the best and/or most honest way of packaging it with the VGMs (for PMH, not here)? Especially if it's a monaural song that would be presented in stereo by the hardware...
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