mirror of https://github.com/bsnes-emu/bsnes.git
10 Commits
| Author | SHA1 | Message | Date |
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Tim Allen
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04072b278b |
Update to v102r16 release.
byuu says:
Changelog:
- Emulator::Stream now allows adding low-pass and high-pass filters
dynamically
- also accepts a pass# count; each pass is a second-order biquad
butterworth IIR filter
- Emulator::Stream no longer automatically filters out >20KHz
frequencies for all streams
- FC: added 20Hz high-pass filter; 20KHz low-pass filter
- GB: removed simple 'magic constant' high-pass filter of unknown
cutoff frequency (missed this one in the last WIP)
- GB,SGB,GBC: added 20Hz high-pass filter; 20KHz low-pass filter
- MS,GG,MD/PSG: added 20Hz high-pass filter; 20KHz low-pass filter
- MD: added save state support (but it's completely broken for now;
sorry)
- MD/YM2612: fixed Voice#3 per-operator pitch support (fixes sound
effects in Streets of Rage, etc)
- PCE: added 20Hz high-pass filter; 20KHz low-pass filter
- WS,WSC: added 20Hz high-pass filter; 20KHz low-pass filter
So, the point of the low-pass filters is to remove frequencies above
human hearing. If we don't do this, then resampling will introduce
aliasing that results in sounds that are audible to the human ear. Which
basically an annoying buzzing sound. You'll definitely hear the
improvement from these in games like Mega Man 2 on the NES. Of course,
these already existed before, so this WIP won't sound better than
previous WIPs.
The high-pass filters are a little more complicated. Their main role is
to remove DC bias and help to center the audio stream. I don't
understand how they do this at all, but ... that's what everyone who
knows what they're talking about says, thus ... so be it.
I have set all of the high-pass filters to 20Hz, which is below the
limit of human hearing. Now this is where it gets really interesting ...
technically, some of these systems actually cut off a lot of range. For
instance, the GBA should technically use an 800Hz high-pass filter when
output is done through the system's speakers. But of course, if you plug
in headphones, you can hear the lower frequencies.
Now 800Hz ... you definitely can hear. At that level, nearly all of the
bass is stripped out and the audio is very tinny. Just like the real
system. But for now, I don't want to emulate the audio being crushed
that badly.
I'm sticking with 20Hz everywhere since it won't negatively affect audio
quality. In fact, you should not be able to hear any difference between
this WIP and the previous WIP. But theoretically, DC bias should mostly
be removed as a result of these new filters. It may be that we need to
raise the values on some cores in the future, but I don't want to do
that until we know for certain that we have to.
What I can say is that compared to even older WIPs than r15 ... the
removal of the simple one-pole low-pass and high-pass filters with the
newer three-pass, second-order filters should result in much better
attenuation (less distortion of audible frequencies.) Probably not
enough to be noticeable in a blind test, though.
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Tim Allen
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7e7003fd29 |
Update to v102r15 release.
byuu says:
Changelog:
- nall: added DSP::IIR::OnePole (which is a first-order IIR filter)
- FC/APU: removed strong highpass, weak hipass filters (and the
dummied out lowpass filter)
- MS,GG,MD/PSG: removed lowpass filter
- MS,GG,MD/PSG: audio was not being centered properly; removed
centering for now
- MD/YM2612: fixed clipping of accumulator from 18 signed bits to 14
signed bits (-0x2000 to +0x1fff) [Cydrak]
- MD/YM2612: removed lowpass filter
- PCE/PSG: audio was not being centered properly; removed centering
for now
First thing is that I've removed all of the ad-hoc audio filtering.
Emulator::Stream intrinsically provides a three-pass, second-order
biquad IIR butterworth lowpass filter that clips frequencies above 20KHz
with very good attenuation (as good as IIR gets, anyway.)
It doesn't really make sense to have the various cores running
additional lowpass filters. If we want to filter frequencies below
20KHz, then I can adapt Emulator::Audio::createStream() to take a cutoff
frequency value, and we can do it all at once, with much better quality.
Right now, I don't know what frequencies are best to cut off the various
other audio cores, so they're just gone for now.
As for the highpass filters for the Famicom core, well ... you don't get
aliasing from resampling low frequencies. And generally speaking, too
low a frequency will be inaudible anyway. All these were doing was
killing possible bass (if they were too strong.) We can add them again,
but only if someone can convert Ryphecha's ad-hoc magic integers into a
frequency cutoff. In which case, I'll use my biquad IIR filter to do it
even better. On this note, it may prove useful to do this for the MD PSG
as well, to try and head off unnecessary clamping when mixing with the
YM2612.
Finally, there was the audio centering issue that affected the
MS,GG,MD,PCE,SG cores. It was flooring the "silent" audio level, which
was resulting in extremely heavy distortion if you tried listening to
higan and, say, audacious at the same time. Without the botched
centering, this distortion is completely gone now.
However, without any centering, we've halved the potential volume range.
This means the audio slider in higan's audio settings panel will start
clamping twice as quickly. So ultimately, we need to figure out how to
fix the centering. This isn't as simple as just subtracting less. We
will probably have to center every individual audio channel before
summing them to do this properly.
Results:
On the Mega Drive, Altered Beast sounds quite a bit better, a lot less
distortion now. But it's still not perfect, especially sound effects.
Further, Bare Knuckle / Streets of Rage still has really bad sound
effects. It looks like I broke something in Cydrak's code when trying to
adapt it to my style =(
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Tim Allen
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89d47914b9 |
Update to v102r14 release.
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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Tim Allen
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1cab2dfeb8 |
Update to v102r11 release.
byuu says:
Changelog:
- MD: connected 32KB cartridge RAM up to every Genesis game under 2MB
loaded¹
- MS, GG, MD: improved PSG noise channel emulation, hopefully²
- MS, GG, MD: lowered PSG volume so that the lowpass doesn't clamp
samples³
- MD: added read/write handlers for VRAM, VSRAM, CRAM
- MD: block VRAM copy when CD4 is clear⁴
- MD: rewrote VRAM fill, VRAM copy to be byte-based⁵
- MD: VRAM fill byte set should fall through to regular data port
write handler⁶
¹: the header parsing for backup RAM is really weird. It's spaces
when not used, and seems to be 0x02000001-0x02003fff for the Shining
games. I don't understand why it starts at 0x02000001 instead of
0x02000000. So I'm just forcing every game to have 32KB of RAM for now.
There's also special handling for ROMs > 2MB that also have RAM
(Phantasy Star IV, etc) where there's a toggle to switch between ROM and
RAM. For now, that's not emulated.
I was hoping the Shining games would run after this, but they're still
dead-locking on me :(
²: Cydrak pointed out some flaws in my attempt to implement what he
had. I was having trouble understanding what he meant, so I went back
and read the docs on the sound chip and tried implementing the counter
the way the docs describe. Hopefully I have this right, but I don't know
of any good test ROMs to make sure my noise emulation is correct. The
docs say the shifted-out value goes to the output instead of the low bit
of the LFSR, so I made that change as well.
I think I hear the noise I'm supposed to in Sonic Marble Zone now, but
it seems like it's not correct in Green Hill Zone, adding a bit of an
annoying buzz to the background music. Maybe it sounds better with the
YM2612, but more likely, I still screwed something up :/
³: it's set to 50% range for both cores right now. For the MD, it
will need to be 25% once YM2612 emulation is in.
⁴: technically, this deadlocks the VDP until a hard reset. I could
emulate this, but for now I just don't do the VRAM copy in this case.
⁵: VSRAM fill and CRAM fill not supported in this new mode. They're
technically undocumented, and I don't have good notes on how they work.
I've been seeing conflicting notes on whether the VRAM fill buffer is
8-bits or 16-bits (I chose 8-bits), and on whether you write the low
byte and then high byte of each words, or the high byte and then low
byte (I chose the latter.)
The VRAM copy improvements fix the opening text in Langrisser II, so
that's great.
⁶: Langrisser II sets the transfer length to one less than needed to
fill the background letter tile on the scenario overview screen. After
moving to byte-sized transfers, a black pixel was getting stuck there.
So effectively, VRAM fill length becomes DMA length + 1, and the first
byte uses the data port so it writes a word value instead of just a byte
value. Hopefully this is all correct, although it probably gets way more
complicated with the VDP FIFO.
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Tim Allen
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68f04c3bb8 |
Update to v102r10 release.
byuu says: Changelog: - removed Emulator::Interface::Capabilities¹ - MS: improved the PSG emulation a bit - MS: added cheat code support - MS: added save state support² - MD: emulated the PSG³ ¹: there's really no point to it anymore. I intend to add cheat codes to the GBA core, as well as both cheat codes and save states to the Mega Drive core. I no longer intend to emulate any new systems, so these values will always be true. Further, the GUI doesn't respond to these values to disable those features anymore ever since the hiro rewrite, so they're double useless. ²: right now, the Z80 core is using a pointer for HL-\>(IX,IY) overrides. But I can't reliably serialize pointers, so I need to convert the Z80 core to use an integer here. The save states still appear to work fine, but there's the potential for an instruction to execute incorrectly if you're incredibly unlucky, so this needs to be fixed as soon as possible. Further, I still need a way to serialize array<T, Size> objects, and I should also add nall::Boolean serialization support. ³: I don't have a system in place to share identical sound chips. But this chip is so incredibly simple that it's not really much trouble to duplicate it. Further, I can strip out the stereo sound support code from the Game Gear portion, so it's even tinier. Note that the Mega Drive only just barely uses the PSG. Not at all in Altered Beast, and only for a tiny part of the BGM music on Sonic 1, plus his jump sound effect. |
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Tim Allen
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8071da4c6a |
Update to v102r09 release.
byuu says:
Changelog:
- MD: restructured DMA to a subclass of VDP
- MD: implemented VRAM copy mode (fixes Langrisser II ... mostly)
- MS: implemened PSG support [Cydrak]
- GG: implemented PSG stereo sound support
- MS: use the new struct Model {} design that other cores use
The MS/GG PSG should be feature complete, but I don't have good tests
for Game Gear stereo mode, nor for the noise channel. There's also a
really weird behavior with when to reload the channel counters on volume
register writes. I can confirm what Cydrak observed in that following
the docs and reloading always creates serious audio distortion problems.
So, more research is needed there.
To get the correct sound out of the PSG, I have to run it at 3.58MHz /
16, which seems really weird to me. The docs make it sound like it's
supposed to run at the full 3.58MHz. If we can really run it at
223.7KHz, then that's help reduce the overhead of PSG emulation, which
will definitely come in handy for Mega Drive, and possibly later Mega
CD, emulation.
I have not implemented the PSG into the Mega Drive just yet. Nor have I
implemented save states or cheat code support into the MS/GG cores yet.
The latter is next on my list.
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Tim Allen
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bf90bdfcc8 |
Update to v101r31 release.
byuu says:
Changelog:
- converted Emulator::Interface::Bind to Emulator::Platform
- temporarily disabled SGB hooks
- SMS: emulated Game Gear palette (latching word-write behavior not
implemented yet)
- SMS: emulated Master System 'Reset' button, Game Gear 'Start' button
- SMS: removed reset() functionality, driven by the mappable input now
instead
- SMS: split interface class in two: one for Master System, one for
Game Gear
- SMS: emulated Game Gear video cropping to 160x144
- PCE: started on HuC6280 CPU core—so far only registers, NOP
instruction has been implemented
Errata:
- Super Game Boy support is broken and thus disabled
- if you switch between Master System and Game Gear without
restarting, bad things happen:
- SMS→GG, no video output on the GG
- GG→SMS, no input on the SMS
I'm not sure what's causing the SMS\<-\>GG switch bug, having a hard
time debugging it. Help would be very much appreciated, if anyone's up
for it. Otherwise I'll keep trying to track it down on my end.
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Tim Allen
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bab2ac812a |
Update to v101r24 release.
byuu says:
Changelog:
- SMS: extended bus mapping of in/out ports: now decoding them fully
inside ms/bus
- SMS: moved Z80 disassembly code from processor/z80 to ms/cpu
(cosmetic)
- SMS: hooked up non-functional silent PSG sample generation, so I can
cap the framerate at 60fps
- SMS: hooked up the VDP main loop: 684 clocks/scanline, 262
scanlines/frame (no PAL support yet)
- SMS: emulated the VDP Vcounter and Hcounter polling ... hopefully
it's right, as it's very bizarre
- SMS: emulated VDP in/out ports (data read, data write, status read,
control write, register write)
- SMS: decoding and caching all VDP register flags (variable names
will probably change)
- nall: \#undef IN on Windows port (prevent compilation warning on
processor/z80)
Watching Sonic the Hedgehog, I can definitely see some VDP register
writes going through, which is a good sign.
Probably the big thing that's needed before I can get enough into the
VDP to start showing graphics is interrupt support. And interrupts are
never fun to figure out :/
What really sucks on this front is I'm flying blind on the Z80 CPU core.
Without a working VDP, I can't run any Z80 test ROMs to look for CPU
bugs. And the CPU is certainly too buggy still to run said test ROM
anyway. I can't find any SMS emulators with trace logging from reset.
Such logs vastly accelerate tracking down CPU logic bugs, so without
them, it's going to take a lot longer.
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Tim Allen
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0b70a01b47 |
Update to v101r10 release.
byuu says:
Changelog:
- 68K: MOVEQ is 8-bit signed
- 68K: disassembler was print EOR for OR instructions
- 68K: address/program-counter indexed mode had the signed-word/long
bit backward
- 68K: ADDQ/SUBQ #n,aN always works in long mode; regardless of size
- 68K→VDP DMA needs to use `mode.bit(0)<<22|dmaSource`; increment by
one instead of two
- Z80: added registers and initial two instructions
- MS: hooked up enough to load and start running games
- Sonic the Hedgehog can execute exactly one instruction... whoo.
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Tim Allen
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043f6a8b33 |
Update to v101r08 release.
byuu says:
Changelog:
- 68K: fixed read-modify-write instructions
- 68K: fixed ADDX bug (using wrong target)
- 68K: fixed major bug with SUB using wrong argument ordering
- 68K: fixed sign extension when reading address registers from
effective addressing
- 68K: fixed sign extension on CMPA, SUBA instructions
- VDP: improved OAM sprite attribute table caching behavior
- VDP: improved DMA fill operation behavior
- added Master System / Game Gear stubs (needed for developing the Z80
core)
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