FM PCM Player 1.0 released

Nice job! I would never expect that pure FM chip could do that

I'm wondering how well does it work with the FPGA implementations of OPLL. Can't test myself right now as i'm packing stuff (moving to new apartment soon) but i'll do when i have a chance if nobody tries it before

Wow! How is this possible?! The sound is just very good! Nice!

Very cool. Can this only be done with the YM2413?

Yes, that is a simple matter of replacing an ld a,(hl) by an in a,(98H).

In principle it can be done with all Yamaha OP* chips since all of them have the phase generator hold function in the test register.

However there is one catch; the OPLL has a 9-bit f-num, and by setting only the LSB you can reach the entire amplitude range quite easily. The OPL series however have a 10-bit f-num, and as a result the LSB only has half the range. It is preferred to only change one register because if you need to change multiple it will introduce noise. I think the LSB’s range can be increased by involving the modulator though.

I want to experiment with getting this to work on the OPL series as well, just for completeness’ sake. For OPL4 the benefit would be that this allows streaming PCM of arbitrary length, something which it normally can’t do. As for MSX-AUDIO and OPNA, they have a more direct register in their ADPCM unit that allows PCM output without silencing FM playback, so that is the more obvious option. Nevertheless it would also be interesting to try it out on the OPN series.

Sorry for not getting at first! As @Grauw said, it's not, but it's the one where it would be most useful at first.

Excellent work! I didn't follow the forum thread (sorry), is this solution suitable for games?

I tried it tonight and I can confirm that indeed this can also work on MSX-AUDIO and MoonSound.

I can also confirm this is indeed the case. Tonight’s test therefore used carrier multiplier 8 (instead of 4 on the OPLL) to index in a quarter sine. I can double the amplitude by selecting the additive algorithm but it does have DC offset. I will fiddle around with modulator settings next to get rid of the DC offset.

I don't think so, it is like that on the OPN series but not on OPL.

But, for implementing this technique on OPN that is actually an interesting observation.

Thanks! The number of channels can be up to 9, however since the YM2413 has a wait requirement of 96 cycles per access, the maximum frequency for >1 channels is determined by the formula 3579545 / 96 / <channel-count>. E.g. for 2 channels the maximum is 18643 Hz and for 4 channels it is 9322 Hz.

However instead of using multiple channels you might as well add all the samples together and play them on a single channel. The downside is a small reduction in bit-depth but on the upside you can have a higher frequency which in my opinion is more important for good sound quality.

Bit-depth affects the noise floor, which isn’t audible during loud music, while frequency determines whether it sounds bright or muffled overall.

For turboR the answer is simple since a MOD player has been done before . The FM method doesn’t really add significant overhead compared to the internal DAC, so it should work equally well. However since its MSX-MUSIC and DAC are output through the same mono jack, you won’t get any stereo, so you might as well just use the internal DAC.

Thanks hope-hunter. Indeed the normal FM synthesis is not possible during the sample playback. The test register bit used by this technique disables the phase increase across all channels…

Well, one more thinking, I also have interesting in modify my OPLL to create a better stereo, like a "professional mixing".
In a studio mixing, we generally use a standart for drums panoramic that works great. It was nice to reproduce it like this.
The bass works better on center. The Snare Drum could be also on center. The toms, Hi-Hat and Crash has their own panoramic: Tom a little to left (or according his frequency), Hi-Hat a little to right, and crash a little more to right or left (or also according his frequency).
On tone instruments, each channel could be reproduce with a different panoramic. Like: Center, Center, Left, Left, Right, Right or another "scenes" to select.
I'm like to try manually do this using two OPLLs CI, masking the bits. But maybe more easy to emulate this.
I think this improvement would not change the originally os the old OPLL musics and it would be all automatic.

OpenMSX has integrated Nuke.YKT’s Nuked-OPLL core since version 16, which is accurate enough to play back PCM.

Hmm good question. I haven’t looked in to it, but a problem is that you can not define a custom instrument, so you can’t set a high multiplier on the carrier, and the range and amplitude of values you can output will be limited.