mirror of https://github.com/bsnes-emu/bsnes.git
89d47914b9
byuu says:
Changelog:
- (MS,GG,MD)/PSG: flip output bit from noise channel [TmEE]
- MD/YM2612: rewrite YM2612::Channel functions to
YM2612::Channel::Operator functions¹
- MD/YM2612: pitch/octave I/O registers should set reload, not value
(fixes sound in most games)
- MD/YM2612: don't try to sign-extend raw PCM values (fixes Shining
Force opening music)
- MD/YM2612: various algorithm simplifications; conversions from
`*`, `/`, `%` to `<<`, `>>`; etc.
Overall ... Sonic the Hedgehog sounds really, really great. Almost
perfect, but there's a bit of clamping going on in the special zones.
Langrisser II sounds really great. Shining Force sounds pretty much
perfect. Bare Knucles (Streets of Rage) does pretty badly ... punches
sound more like dinging a salad fork on a wine glass, heh. Altered Beast
is extremely broken ... no music at the title screen, very distorted
in-game music. I suspect a bug outside of the YM2612 is affecting this
game.
So, the YM2612 emulation isn't perfect, but it's a really good start to
the most complex sound chip in all of higan. Hopefully the VRC7 and
YM2413 will prove to be less ferocious ... not that I'm in any rush to
work on either. The former is going to need the NES mapper rewrite to be
done first, and the latter is cool but not very necessary since all
those games have fallbacks to the inferior PSG audio.
But really ... I can't thank Cydrak enough for doing this for me. It
would have probably taken me months to parse through all of the
documentation on this chip (most of which is in a 55-page thread on
spritesmind that is filled with wrong/outdated information at the start,
and corrections as you go deeper.) Not to mention, learning about what
the hell detuning, low-frequency oscillation, tremolo, vibrato, etc were
all about. Or how those algorithms to compute the final output work. Or
the dozens of special cases littered in there to make everything sound
good. Fierce, nasty chip that.
Now the last real problem is save states ... the Mega Drive is going to
be the trickiest of all to implement with libco. There are lots of areas
where one chip will deadlock another chip while it completes some
operation. We don't have a choice but to force those stalls to abort
anyway, in order to let libco reach the start of its entry point once
again. I don't know what kind of impact that'll have on states ... I
suspect they'll work almost as reliably as the SNES does, but I can't
know that until I implement it. It's going to be pretty nasty, though.
¹: this basically removes a lot of unnecessary op. prefixes and the
need to capture `auto& op = operators[index]` at the start of every
function.
I wanted to have subfunctions like
`YM2612::Channel::Operator::Envelope::run()`, etc but unfortunately,
pretty much all of the envelope, phase, pitch, level functions need to
access each other's state.
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| .. | ||
| apu | ||
| bus | ||
| cartridge | ||
| controller | ||
| cpu | ||
| interface | ||
| psg | ||
| system | ||
| vdp | ||
| ym2612 | ||
| GNUmakefile | ||
| md.hpp | ||