byuu says:
Changelog:
- improved attenuation of biquad filter by computing butterworth Q
coefficients correctly (instead of using the same constant)
- adding 1e-25 to each input sample into the biquad filters to try and
prevent denormalization
- updated normalization from [0.0 to 1.0] to [-1.0 to +1.0]; volume/reverb
happen in floating-point mode now
- good amount of work to make the base Emulator::Audio support any number
of output channels
- so that we don't have to do separate work on left/right channels;
and can instead share the code for each channel
- Emulator::Interface::audioSample(int16 left, int16 right); changed to:
- Emulator::Interface::audioSample(double* samples, uint channels);
- samples are normalized [-1.0 to +1.0]
- for now at least, channels will be the value given to
Emulator::Audio::reset()
- fixed GUI crash on startup when audio driver is set to None
I'm probably going to be updating ruby to accept normalized doubles as
well; but I'm not sure if I will try and support anything other 2-channel
audio output. It'll depend on how easy it is to do so; perhaps it'll be
a per-driver setting.
The denormalization thing is fierce. If that happens, it drops the
emulator framerate from 220fps to about 20fps for Game Boy emulation. And
that happens basically whenever audio output is silent. I'm probably
also going to make a nall/denormal.hpp file at some point with
platform-specific functionality to set the CPU state to "denormals as
zero" where applicable. I'll still add the 1e-25 offset (inaudible)
as another fallback.
byuu says:
Changelog:
- nall/dsp returns with new iir/biquad.hpp and resampler/cubic.hpp files
- nall/queue.hpp added (simple ring buffer ... nall/vector wouldn't
cause too many moves with FIFO)
- audio streams now only buffer 20ms; so even if multiple audio streams
desync, latency can never exceed 20ms
- replaced blackman windwed sinc FIR hermite audio filter with transposed
direct form II biquadratic sixth-order IIR butterworth filter (better
attenuation of frequencies above 20KHz, faster, no need for decimation,
less code)
- put in experimental eight-tap echo filter (a lot better than what I
had before, but still rather weak)
- substantial cleanups to the SuperFX GSU processor core (slightly
faster, 479KB->100KB object file, 42.7KB->33.4KB source code size,
way less code duplication)
We'll definitely want to test the whole SuperFX library (not many games)
just to make sure there's no regressions caused by this one.
Not sure what I want to do with audio processing effects yet. I've always
really wanted lots of fun controls to customize audio, and now finally
with this new biquad filter, I can finally start implementing real
effects. For instance, an equalizer wouldn't be too complicated anymore.
The new reverb effect is still a poor man's version. I need to find human
readable source for implementing a comb-filter properly. I'm pretty sure
I can already treat nall::queue as an all-pass filter since all that
does is phase shift (fancy audio term for "delay audio"). What's really
going to be hard is figuring out how to expose user-friendly settings for
controlling it. It looks like you need a bunch of coprime coefficients,
and I don't think casual users are going to be able to hand-enter coprime
values to get the echo effect they want. I uh ... don't even know how
to calculate coprime values dynamically right now >_> But we're going
to have to, as they are correlated to the output sampling rate.
We'll definitely want to make some audio profiles so that users can
quickly select pre-configured themes that sound nice, but expose the
underlying coefficients so that they can tweak stuff to their liking. This
isn't just about higan, this is about me trying to learn digital signal
processing, so please don't be too upset about feature creep or anything
on this.
Anyway ... I'm having some difficulties with my audio right now. When
the reverb effect is enabled, there's a bunch of static on system
reset for just a moment. But this should not be possible. nall::queue
is initializing all previous reverb sample elements to 0.0. I don't
understand where static is coming in from. Further, we have the same
issue with both the windowed sinc and the biquad filters ... a bit of
a popping sound when starting a game. Any help tracking this down would
be appreciated.
There's also one really annoying issue ... I can't seem to do reverb
or volume adjustments with normalized samples. If I say "volume *= 0.5"
in higan/audio/audio.cpp line 68, it doesn't just halve the volume, it
adds a whole bunch of distortion. This makes absolutely zero sense to
me. The sample values are between 0.0 (mute) and 1.0 (full volume) here,
so multiplying a double by 0.5 shouldn't cause distortion. So right now,
I'm doing these adjustments with less precision after denormalizing back
to int16. Anyone ever see something like that? :/
byuu says:
Changelog:
- nall/vector rewritten from scratch
- higan/audio uses nall/vector instead of raw pointers
- higan/sfc/coprocessor/sdd1 updated with new research information
- ruby/video/glx and ruby/video/glx2: fuck salt glXSwapIntervalEXT!
The big change here is definitely nall/vector. The Windows, OS X and Qt
ports won't compile until you change some first/last strings to
left/right, but GTK will compile.
I'd be really grateful if anyone could stress-test nall/vector. Pretty
much everything I do relies on this class. If we introduce a bug, the
worst case scenario is my entire SFC game dump database gets corrupted,
or the byuu.org server gets compromised. So it's really critical that we
test the hell out of this right now.
The S-DD1 changes mean you need to update your installation of icarus
again. Also, even though the Lunar FMV never really worked on the
accuracy core anyway (it didn't initialize the PPU properly), it really
won't work now that we emulate the hard-limit of 16MiB for S-DD1 games.
byuu says:
Changelog:
- GB: support modeSelect and RAM for MBC1M (Momotarou Collection)
- audio: implemented native resampling support into Emulator::Stream
- audio: removed nall::DSP completely
Unfortunately, the new resampler didn't turn out quite as fast as I had
hoped. The final hermite resampling added some overhead; and I had to
bump up the kernel count to 500 from 400 to get the buzzing to go away
on my main PC. I think that's due to it running at 48000hz output
instead of 44100hz output, maybe?
Compared to Ryphecha's:
(NES) Mega Man 2: 167fps -> 166fps
(GB) Mega Man II: 224fps -> 200fps
(WSC) Riviera: 143fps -> 151fps
Odd that the WS/WSC ends up faster while the DMG/CGB ends up slower.
But this knocks 922 lines down to 146 lines. The only files left in all
of higan not written (or rewritten) by me are ruby/xaudio2.h and
libco/ppc.c
Tim Allen