Overclocking: Changed APU behavior when adding extra lines before/after NMI (helps reduce overclocking-related issues)

Core/APU.cpp

@@ -11,6 +11,7 @@
 #include "MemoryManager.h"
 
 APU* APU::Instance = nullptr;
+bool APU::_apuEnabled = true;
 
 APU::APU(MemoryManager* memoryManager)
 {
@@ -20,6 +21,8 @@ APU::APU(MemoryManager* memoryManager)
 
 	_nesModel = NesModel::Auto;
 
+	_apuEnabled = true;
+
 	_mixer.reset(new SoundMixer());
 
 	_squareChannel[0].reset(new SquareChannel(AudioChannel::Square1, _mixer.get(), true));
@@ -202,6 +205,7 @@ void APU::EndFrame()
 
 void APU::Reset(bool softReset)
 {
+	_apuEnabled = true;
 	_cyclesNeeded = 0;
 	_currentCycle = 0;
 	_previousCycle = 0;
@@ -236,4 +240,18 @@ void APU::StreamState(bool saving)
 void APU::AddExpansionAudioDelta(AudioChannel channel, int16_t delta)
 {
 	Instance->_mixer->AddDelta(channel, Instance->_currentCycle, delta);
+}
+
+void APU::SetApuStatus(bool enabled)
+{
+	_apuEnabled = enabled;
+}
+
+bool APU::IsApuEnabled()
+{
+	//Adding extra lines before/after NMI temporarely turns off the APU
+	//This appears to result in less side-effects than spreading out the APU's
+	//load over the entire PPU frame, like what was done before.
+	//This is most likely due to the timing of the Frame Counter & DMC IRQs.
+	return _apuEnabled;
 }

Core/APU.h

@@ -20,6 +20,7 @@ class APU : public Snapshotable, public IMemoryHandler
 {
 	private:
 		static APU* Instance;
+		static bool _apuEnabled;
 
 		uint32_t _previousCycle;
 		uint32_t _currentCycle;
@@ -65,13 +66,15 @@ class APU : public Snapshotable, public IMemoryHandler
 
 		__forceinline static void ExecStatic()
 		{
-			if(EmulationSettings::GetOverclockRate(true) == 100) {
-				Instance->Exec();
-			} else {
-				Instance->_cyclesNeeded += 1.0 / ((double)EmulationSettings::GetOverclockRate(true) / 100.0);
-				while(Instance->_cyclesNeeded >= 1.0) {
+			if(APU::_apuEnabled) {
+				if(EmulationSettings::GetOverclockRate() == 100 || !EmulationSettings::GetOverclockAdjustApu()) {
 					Instance->Exec();
-					Instance->_cyclesNeeded--;
+				} else {
+					Instance->_cyclesNeeded += 1.0 / ((double)EmulationSettings::GetOverclockRate() / 100.0);
+					while(Instance->_cyclesNeeded >= 1.0) {
+						Instance->Exec();
+						Instance->_cyclesNeeded--;
+					}
 				}
 			}
 		}
@@ -79,4 +82,6 @@ class APU : public Snapshotable, public IMemoryHandler
 		static void StaticRun();
 
 		static void AddExpansionAudioDelta(AudioChannel channel, int16_t delta);
+		static void SetApuStatus(bool enabled);
+		static bool IsApuEnabled();
 };

Core/BaseExpansionAudio.h

@@ -2,6 +2,7 @@
 #include "stdafx.h"
 #include "Snapshotable.h"
 #include "EmulationSettings.h"
+#include "APU.h"
 
 class BaseExpansionAudio : public Snapshotable
 {
@@ -19,13 +20,15 @@ protected:
 public:
 	void Clock()
 	{
-		if(EmulationSettings::GetOverclockRate(true) == 100) {
-			ClockAudio();
-		} else {
-			_clocksNeeded += 1.0 / ((double)EmulationSettings::GetOverclockRate(true) / 100);
-			while(_clocksNeeded >= 1.0) {
+		if(APU::IsApuEnabled()) {
+			if(EmulationSettings::GetOverclockRate() == 100 || !EmulationSettings::GetOverclockAdjustApu()) {
 				ClockAudio();
-				_clocksNeeded--;
+			} else {
+				_clocksNeeded += 1.0 / ((double)EmulationSettings::GetOverclockRate() / 100);
+				while(_clocksNeeded >= 1.0) {
+					ClockAudio();
+					_clocksNeeded--;
+				}
 			}
 		}
 	}

Core/EmulationSettings.cpp

@@ -43,7 +43,6 @@ uint32_t EmulationSettings::_extraScanlinesBeforeNmi = 0;
 uint32_t EmulationSettings::_extraScanlinesAfterNmi = 0;
 uint32_t EmulationSettings::_ppuScanlineCount = 262;
 double EmulationSettings::_effectiveOverclockRate = 100;
-double EmulationSettings::_effectiveOverclockRateSound = 100;
 bool EmulationSettings::_overclockAdjustApu = true;
 bool EmulationSettings::_disableOverclocking = false;
 

Core/EmulationSettings.h

@@ -677,13 +677,12 @@ public:
 	static void UpdateEffectiveOverclockRate()
 	{
 		if(_disableOverclocking) {
-			_effectiveOverclockRateSound = 100;
 			_effectiveOverclockRate = 100;
 		} else {
-			_effectiveOverclockRateSound = _overclockRate * (double)(1 + (double)(_extraScanlinesBeforeNmi + _extraScanlinesAfterNmi) / _ppuScanlineCount);
 			_effectiveOverclockRate = _overclockRate;
 		}
 		_hasOverclock = _effectiveOverclockRate != 100;
+		_audioSettingsChanged = true;
 	}
 
 	static void SetPpuScanlineCount(uint32_t scanlineCount)
@@ -708,15 +707,9 @@ public:
 		return _hasOverclock;
 	}
 
-	static double GetOverclockRate(bool forApu = false, bool forSoundMixer = false)
+	static double GetOverclockRate()
 	{
-		if(forApu && _overclockAdjustApu || forSoundMixer) {
-			return _effectiveOverclockRateSound;
-		} else if(!forApu) {
-			return _effectiveOverclockRate;
-		} else {
-			return 100;
-		}
+		return _effectiveOverclockRate;
 	}
 
 	static bool GetOverclockAdjustApu()

Core/PPU.cpp

@@ -1,6 +1,7 @@
 #include "stdafx.h"
 #include "PPU.h"
 #include "CPU.h"
+#include "APU.h"
 #include "EmulationSettings.h"
 #include "VideoDecoder.h"
 #include "Debugger.h"
@@ -109,16 +110,22 @@ void PPU::SetNesModel(NesModel model)
 		case NesModel::NTSC:
 			_nmiScanline = 241;
 			_vblankEnd = 260;
+			_standardNmiScanline = 241;
+			_standardVblankEnd = 260;
 			EmulationSettings::SetPpuScanlineCount(262);
 			break;
 		case NesModel::PAL:
 			_nmiScanline = 241;
 			_vblankEnd = 310;
+			_standardNmiScanline = 241;
+			_standardVblankEnd = 310;
 			EmulationSettings::SetPpuScanlineCount(312);
 			break;
 		case NesModel::Dendy:
 			_nmiScanline = 291;
 			_vblankEnd = 310;
+			_standardNmiScanline = 291;
+			_standardVblankEnd = 310;
 			EmulationSettings::SetPpuScanlineCount(312);
 			break;
 	}
@@ -1000,6 +1007,20 @@ void PPU::TriggerNmi()
 	}
 }
 
+void PPU::UpdateApuStatus()
+{
+	APU::SetApuStatus(true);
+	if(_scanline > 240) {
+		if(_scanline > _standardVblankEnd) {
+			//Disable APU for extra lines after NMI
+			APU::SetApuStatus(false);
+		} else if(_scanline < _standardNmiScanline) {
+			//Disable APU for extra lines before NMI
+			APU::SetApuStatus(false);
+		}
+	}
+}
+
 void PPU::Exec()
 {
 	if(_cycle > 339) {
@@ -1011,6 +1032,8 @@ void PPU::Exec()
 		}
 
 		Debugger::ProcessPpuCycle();
+		
+		UpdateApuStatus();
 
 		//Cycle = 0
 		if(_scanline == -1) {
@@ -1137,5 +1160,7 @@ void PPU::StreamState(bool saving)
 		}
 
 		_lastUpdatedPixel = -1;
+
+		UpdateApuStatus();
 	}
 }

Core/PPU.h

@@ -48,6 +48,8 @@ class PPU : public IMemoryHandler, public Snapshotable
 		uint16_t *_outputBuffers[2];
 
 		NesModel _nesModel;
+		uint16_t _standardVblankEnd;
+		uint16_t _standardNmiScanline;
 		uint16_t _vblankEnd;
 		uint16_t _nmiScanline;
 
@@ -137,6 +139,8 @@ class PPU : public IMemoryHandler, public Snapshotable
 		void UpdateGrayscaleAndIntensifyBits();
 		virtual void SendFrame();
 
+		void UpdateApuStatus();
+
 		PPURegisters GetRegisterID(uint16_t addr)
 		{
 			if(addr == 0x4014) {

Core/SoundMixer.cpp

@@ -166,7 +166,7 @@ void SoundMixer::UpdateRates(bool forceUpdate)
 {
 	uint32_t newRate = CPU::GetClockRate(_model);
 	if(!EmulationSettings::GetOverclockAdjustApu()) {
-		newRate = (uint32_t)(newRate * (double)EmulationSettings::GetOverclockRate(false, true) / 100);
+		newRate = (uint32_t)(newRate * (double)EmulationSettings::GetOverclockRate() / 100);
 	}
 
 	if(_clockRate != newRate || forceUpdate) {