VGMPlay for MSX

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By Pencioner

Master (212)

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13-11-2017, 13:28

I can't believe - i just tried to google Doom II tracks with no luck and then i refresh this thread - voila. The mistery! Running Naked in a Field of Flowers

By ImATrackMan

Resident (58)

ImATrackMan's picture

13-11-2017, 22:32

Grauw wrote:

Note that as for the YM2608 OPNA, YM2610 OPNB and YM2610 OPN2, their clock may be listed as 8 MHz, however it is internally divided to 4 MHz so the pitch difference is similar to the OPN, just a few semitones.]

I had a look through the YM2151 application manual, for a podcast's MSX music episode and it said the same thing of the OPM/OPP. The input clock is internally divided by 2 on that as well.

Grauw wrote:
ImATrackMan wrote:

As an experiment I wanted to see if merged VGM files would work. They do but with a couple of drawbacks I guess? The file plays and the actual note timing is correct, but I think the chips start playing at different times (SFG comes in a while after the OPL4 but I may be misremembering).

Indeed! Both play, but the OPM part starts 7 seconds late, and the tracks are misaligned. Seems like that should be fixable… It sounds nice otherwise! Smile

Thank you!

By Grauw

Enlighted (6262)

Grauw's picture

14-11-2017, 00:38

Actually I simplified things a bit previously;

The OPM/OPP takes 2 master clock cycles per operator, with 8 channels of 4 operators each it totals 64 cycles per sample. Indeed internally it is divided by two.

The OPN takes 6 master clock cycles per operator, with 3 channels of 4 operators each it totals 72 cycles per sample. Since there are twice as much channels on OPNA, OPNB and OPN2 it takes 144 cycles per sample, they doubled the master clock frequency to compensate for that so that the same f-nums could be used as the OPN and backwards compatibility is preserved. This was the “division” I referred to.

However the OPN series is actually internally predivided by 6. The OPNA actually also has a prescaler control register which allows to select the master clock division to feed the internal clock, choosing 6, 3 or 2 for FM and 4, 2, 1 for SSG. The default division is 6, meant for 8 MHz.

(Note that this also means that the OPNA can be fed from a 3.58 MHz clock, although the ADPCM and drums will not be affected by the setting and play at too low a frequency, so it’s not recommended.)

By Parn

Master (208)

Parn's picture

14-11-2017, 00:58

Grauw, I just wanted to report something weird that happened last week, during the Jaú MSX Meeting. I traded my old FM-X (a Brazilian MSX-Music cartridge made by DDX) for a new FM Sound Stereo (made by Tecnobytes), since the latter has much better sound quality. I used to listen to OPLL soundtracks on my trusty old A1F with the FM-X without issues, but when I tried to play some of the same soundtracks with the FM Sound Stereo, it looked like VGMPlay didn't detect the cartridge. It just played the PSG part if there was one, or nothing at all. The cartridge works perfectly fine otherwise: games use it, and FM-BASIC also works. I tried with another FM Sound Stereo and the same thing happened. Sadly I don't have the FM-X anymore for further testing. I also tried to reproduce the issue on an emulator, without success. Do you have any idea about what might have happened?

I also have a small suggestion. Could you enable Y8950 playback on Moonsound by ignoring the PCM? Most Y8950 packs don't use PCM anyway, and it would be nice being able to listen to Xevious and other Compile soundtracks on Moonsound, since I don't have an MSX-Audio. Only if it's not too much trouble, and if you think it is worth the hassle, of course. Thanks!

By Grauw

Enlighted (6262)

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14-11-2017, 01:33

Parn, that’s odd… I can’t think of anything to explain it. Only thing I know is that FM-PAC is left disabled when there’s an internal MSX-MUSIC, however the A1F does not have one and homebrew MSX-MUSIC cartridges seldom implement the FM-PAC’s disable bit. If you or anyone else has more information, some suggestions or is willing to debug it for me, let me know.

Y8950 on MoonSound, I’ll put it on my list.

By Parn

Master (208)

Parn's picture

14-11-2017, 01:46

Grauw wrote:

If you or anyone else has more information, some suggestions or is willing to debug it for me, let me know.

I'll do more testing. I'm rather intrigued by this. It's not a big deal since I have other MSXs, but it's still weird.

Grauw wrote:

Y8950 on MoonSound, I’ll put it on my list.

Thank you very much!

By Grauw

Enlighted (6262)

Grauw's picture

14-11-2017, 02:24

Does VGMPlay show that it’s detected the MSX-MUSIC (on a line starting with -> after the YM2413)?

If not, MSX-MUSIC detection is done by looking for the magic bytes string in the ROM, so a ROM dump could provide useful information (possibly also make it reproducible in the emulator).

By Parn

Master (208)

Parn's picture

14-11-2017, 22:35

Right now I'm not 100% sure, but I got the impression the cartridge wasn't detected by VGMPlay. I put the A1F in storage due to lack of space in my workbench, but I'll take it out tomorrow for further testing. And I'll certainly dump the ROM, I'm very curious about it.

By Grauw

Enlighted (6262)

Grauw's picture

15-11-2017, 23:36

Hey Parn, I’ve submitted the Y8950 on MoonSound playback. Note, no ADPCM, since that requires quite a bit more work to convert.

By Pencioner

Master (212)

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16-11-2017, 00:07

Grauw thanks, i'm gonna try it Smile

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