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NES: Non-linear square channel mixer option #68

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Yave-Yu wants to merge 2 commits into from
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NES: Non-linear square channel mixer option #68

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c65f8d3
Added non-linear square channel mixer option
Yave-Yu Apr 26, 2026
762905f
Merge branch 'master' into LinearMixer
Yave-Yu May 2, 2026
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6 changes: 6 additions & 0 deletions Core/NES/APU/ApuTimer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,12 @@ class ApuTimer : public ISerializable
_lastOutput = output;
}
}

__forceinline void SendVolume(uint8_t rawVolume)
{
//Only square channel needs raw volume, for linear mixing
_mixer->RawVolume(_channel, rawVolume);
}

int8_t GetLastOutput()
{
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11 changes: 10 additions & 1 deletion Core/NES/APU/SquareChannel.h
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Expand Up @@ -18,6 +18,13 @@ class SquareChannel : public INesMemoryHandler, public ISerializable
{ 0, 0, 0, 0, 1, 1, 1, 1 },
{ 1, 1, 1, 1, 1, 1, 0, 0 }
};

static constexpr int8_t _dutySequencesUnbiased[4][8] = {
{-1,-1,-1,-1,-1,-1,-1, 7 },
{-2,-2,-2,-2,-2,-2, 6, 6 },
{-4,-4,-4,-4, 4, 4, 4, 4 },
{ 2, 2, 2, 2, 2, 2,-6,-6 },
};

NesConsole* _console = nullptr;
ApuEnvelope _envelope;
Expand Down Expand Up @@ -84,8 +91,10 @@ class SquareChannel : public INesMemoryHandler, public ISerializable
{
if(IsMuted()) {
_timer.AddOutput(0);
_timer.SendVolume(0);
} else {
_timer.AddOutput(_dutySequences[_duty][_dutyPos] * _envelope.GetVolume());
_timer.AddOutput(_console->GetNesConfig().NonlinearSquareMixer ? _dutySequences[_duty][_dutyPos] * _envelope.GetVolume() : _dutySequencesUnbiased[_duty][_dutyPos] * _envelope.GetVolume());
_timer.SendVolume(_envelope.GetVolume());
}
}

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14 changes: 11 additions & 3 deletions Core/NES/NesSoundMixer.cpp
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Expand Up @@ -177,10 +177,13 @@ double NesSoundMixer::GetChannelOutput(AudioChannel channel, bool forRightChanne
int16_t NesSoundMixer::GetOutputVolume(bool forRightChannel)
{
double squareOutput = GetChannelOutput(AudioChannel::Square1, forRightChannel) + GetChannelOutput(AudioChannel::Square2, forRightChannel);
double tndOutput = GetChannelOutput(AudioChannel::DMC, forRightChannel) + 2.7516713261 * GetChannelOutput(AudioChannel::Triangle, forRightChannel) + 1.8493587125 * GetChannelOutput(AudioChannel::Noise, forRightChannel);
double tndOutput = 2.7516713261 * GetChannelOutput(AudioChannel::Triangle, forRightChannel) + 1.8493587125 * GetChannelOutput(AudioChannel::Noise, forRightChannel) + GetChannelOutput(AudioChannel::DMC, forRightChannel);

uint16_t squareVolume = (uint16_t)((95.88 * 5000.0) / (8128.0 / squareOutput + 100.0));
uint16_t tndVolume = (uint16_t)((159.79 * 5000.0) / (22638.0 / tndOutput + 100.0));
//Non-linear square channel mixer flag
double squareVolume = _console->GetNesConfig().NonlinearSquareMixer ?
95.88 / (8128.0 / squareOutput + 100.0) * 5000.0
: squareOutput / 240.0 * squareSumFactor[_squareVolume[(int)AudioChannel::Square1] + _squareVolume[(int)AudioChannel::Square2]] * 0.258483 * 5000.0;
double tndVolume = 159.79 / (1.0 / (tndOutput / 22638.0) + 100.0) * 5000.0;

return (int16_t)(squareVolume + tndVolume +
GetChannelOutput(AudioChannel::FDS, forRightChannel) * 20 +
Expand All @@ -198,6 +201,11 @@ void NesSoundMixer::AddDelta(AudioChannel channel, uint32_t time, int16_t delta)
}
}

void NesSoundMixer::RawVolume(AudioChannel channel, uint8_t rawVolume)
{
_squareVolume[(int)channel] = rawVolume;
}

void NesSoundMixer::EndFrame(uint32_t time)
{
sort(_timestamps.begin(), _timestamps.end());
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3 changes: 3 additions & 0 deletions Core/NES/NesSoundMixer.h
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Expand Up @@ -22,6 +22,7 @@ class NesSoundMixer : public ISerializable
static constexpr uint32_t MaxSampleRate = 96000;
static constexpr uint32_t MaxSamplesPerFrame = MaxSampleRate / 60 * 4 * 2; //x4 to allow CPU overclocking up to 10x, x2 for panning stereo
static constexpr uint32_t MaxChannelCount = 11;
static constexpr double squareSumFactor[31] = { 1.0, 1.352455, 1.336216, 1.320361, 1.304878, 1.289755, 1.274978, 1.260535, 1.246416, 1.232610, 1.219107, 1.205896, 1.192968, 1.180314, 1.167927, 1.155796, 1.143915, 1.132276, 1.120871, 1.109693, 1.098737, 1.087994, 1.077460, 1.067127, 1.056991, 1.047046, 1.037286, 1.027706, 1.018302, 1.009068, 1.0 };

NesConsole* _console = nullptr;
SoundMixer* _mixer = nullptr;
Expand All @@ -36,6 +37,7 @@ class NesSoundMixer : public ISerializable
vector<uint32_t> _timestamps;
int16_t _channelOutput[MaxChannelCount][CycleLength] = {};
int16_t _currentOutput[MaxChannelCount] = {};
uint8_t _squareVolume[2] = {};

blip_t* _blipBufLeft = nullptr;
blip_t* _blipBufRight = nullptr;
Expand Down Expand Up @@ -66,6 +68,7 @@ class NesSoundMixer : public ISerializable

void PlayAudioBuffer(uint32_t cycle);
void AddDelta(AudioChannel channel, uint32_t time, int16_t delta);
void RawVolume(AudioChannel channel, uint8_t rawVolume);

void Serialize(Serializer& s) override;
};
2 changes: 2 additions & 0 deletions Core/Shared/SettingTypes.h
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Expand Up @@ -132,6 +132,7 @@ struct AudioConfig
uint32_t SampleRate = 48000;
uint32_t AudioLatency = 60;

bool NonlinearSquareMixer = true;
bool MuteSoundInBackground = false;
bool ReduceSoundInBackground = true;
bool ReduceSoundInFastForward = false;
Expand Down Expand Up @@ -669,6 +670,7 @@ struct NesConfig
uint32_t PpuExtraScanlinesBeforeNmi = 0;
uint32_t PpuExtraScanlinesAfterNmi = 0;

bool NonlinearSquareMixer = true;
bool DisableNoiseModeFlag = false;
bool ReduceDmcPopping = false;
bool SilenceTriangleHighFreq = false;
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3 changes: 3 additions & 0 deletions UI/Config/NesConfig.cs
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Expand Up @@ -88,6 +88,7 @@ public class NesConfig : BaseConfig<NesConfig>
[Reactive][MinMax(0, 1000)] public UInt32 PpuExtraScanlinesAfterNmi { get; set; } = 0;

//Audio
[Reactive] public bool NonlinearSquareMixer { get; set; } = true;
[Reactive] public bool DisableNoiseModeFlag { get; set; } = false;
[Reactive] public bool ReduceDmcPopping { get; set; } = false;
[Reactive] public bool SilenceTriangleHighFreq { get; set; } = false;
Expand Down Expand Up @@ -207,6 +208,7 @@ public void ApplyConfig()
PpuExtraScanlinesAfterNmi = PpuExtraScanlinesAfterNmi,
PpuExtraScanlinesBeforeNmi = PpuExtraScanlinesBeforeNmi,

NonlinearSquareMixer = NonlinearSquareMixer,
DisableNoiseModeFlag = DisableNoiseModeFlag,
ReduceDmcPopping = ReduceDmcPopping,
SilenceTriangleHighFreq = SilenceTriangleHighFreq,
Expand Down Expand Up @@ -344,6 +346,7 @@ public struct InteropNesConfig
public UInt32 PpuExtraScanlinesBeforeNmi;
public UInt32 PpuExtraScanlinesAfterNmi;

[MarshalAs(UnmanagedType.I1)] public bool NonlinearSquareMixer;
[MarshalAs(UnmanagedType.I1)] public bool DisableNoiseModeFlag;
[MarshalAs(UnmanagedType.I1)] public bool ReduceDmcPopping;
[MarshalAs(UnmanagedType.I1)] public bool SilenceTriangleHighFreq;
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1 change: 1 addition & 0 deletions UI/Localization/resources.en.xml
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Expand Up @@ -321,6 +321,7 @@
<Control ID="chkSwapDutyCycles">Swap square channels duty cycles (mimics old clones)</Control>
<Control ID="chkReverseDpcmBitOrder">Reverse DPCM bit order (higher or lower quality, depends on game)</Control>
<Control ID="chkSilenceTriangleHighFreq">Mute ultrasonic frequencies on triangle channel (reduces popping)</Control>
<Control ID="chkNonlinearSquareMixer">Use non-linear square channel mixer</Control>
<Control ID="chkReduceDmcPopping">Reduce popping sounds on the DMC channel</Control>
<Control ID="chkDisableNoiseModeFlag">Disable noise channel mode flag (mimics oldest Famicom models)</Control>
<Control ID="grpEffects">Effects</Control>
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1 change: 1 addition & 0 deletions UI/Views/NesConfigView.axaml
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Expand Up @@ -102,6 +102,7 @@
<StackPanel>
<c:OptionSection Header="{l:Translate grpGeneral}" Margin="0">
<StackPanel>
<CheckBox IsChecked="{Binding Config.NonlinearSquareMixer}" Content="{l:Translate chkNonlinearSquareMixer}" />
<CheckBox IsChecked="{Binding Config.ReduceDmcPopping}" Content="{l:Translate chkReduceDmcPopping}" />
<CheckBox IsChecked="{Binding Config.SilenceTriangleHighFreq}" Content="{l:Translate chkSilenceTriangleHighFreq}" />
<c:CheckBoxWarning IsChecked="{Binding Config.DisableNoiseModeFlag}" Text="{l:Translate chkDisableNoiseModeFlag}" />
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