digital-sound-antiques / emu2413 Goto Github PK

Grettings,
would you consider to test this on the real hardware, on how the modulator should behave?

First is the modulator envelope precision, and the envelope behavior when key is off after key on.
This file containing .nsf and the .wav of what this API sounded like.
mod release test.zip

Need cherry picking this patch. https://github.com/rururutan/emu2413/commit/5e7b729b3aa218222fdabda1f1f366da94799e17

High frequency noise like top-cym sound tend to be corrupted as 44KHz or lower playback rate, may be because of sample rate conversion.

emu2413 v1.5.7 can not correctly perform ar0test.vgm.zip.

• emu2413: The tone is changed into pure sine from the 3rd note.
• real chip: The tone is changed into pure sine from the 4th note.

ar0test.vgm.zip is genarated from the following MGSDRV MML.

#opll_mode 1
#tempo 150

@v15 = { ;
;       TL FB
        63, 7,
; AR DR SL RR KL MT AM VB EG KR DT
  15, 0, 0,10, 0,15, 0, 0, 1, 0, 0,
  15, 0, 0,10, 0, 1, 0, 0, 1, 0, 0 }

@v16 = { ;
;       TL FB
        63, 7,
; AR DR SL RR KL MT AM VB EG KR DT
   0, 0, 0,10, 0,15, 0, 0, 1, 0, 0,
  15, 0, 0,10, 0, 1, 0, 0, 1, 0, 0 }

9 v15
9 @15 o4 c4 r4 c4 r4 @16 c4 r4 c4 r4

The intention of the MML above is to change the tone from the 3rd note.
The behavior of the real chip is counter-intuitive, but this should be emulated for accuracy.

I'm not too familiar with emu2413, but am working on developing a new tracker which will support VRC7 FM in the future. 0CC-FamiTracker includes a copy of emu2413 from 2004, but I found this repo which seems to be updated.

Looking at master OPLL_calc(), it seems like if opll->quality != 0, you run an unknown number of OPLL cycles (varies with sampling rate), then return the latest sample. Because you do not perform resampling, this will drop synthesized samples (or duplicate them if the speaker sampling rate is over 49716 Hz). Is this right?

Dropping/duplicating audio samples will seriously degrade audio quality. As a resampling method, it converts each discrete-time sample into a continuous-time rectangular non-bandlimited pulse (creating frequency imaging), then samples from that rectangle train (turning the images into aliases). This process generates many unwanted frequencies in the outputted audio.

By comparison, the 2004 version of the library (related to that found in 0CC-FamiTracker) appears to perform linear interpolation, which is less bad for audio quality.

(I think 0CC runs the synth at quality=0, which runs emu2413 at the PC sampling rate, rather than the chip's original rate.)

Also I may use https://www.vogons.org/viewtopic.php?f=9&t=37782 instead. Is that code fast enough for real-time usage?

Degraded from #6. min/max function conflicts with Visual Studio's min/max definition.
These confliction possibly occurs on other platform that defines min/max as macro.