NES: Fixed EPSM sound quality issues

The 500kHz to ~48kHz downsampling was causing problems
SourMesen · Oct 2, 2024 · 1affcd1 · 1affcd1
1 parent 4f423a1
commit 1affcd1
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Showing 3 changed files with 6 additions and 2 deletions.
diff --git a/Core/NES/Epsm.cpp b/Core/NES/Epsm.cpp
@@ -62,16 +62,17 @@ uint64_t Epsm::GetTargetClock()
 
 void Epsm::Exec()
 {
-	constexpr int clocksPerSample = 16;
+	constexpr int clocksPerSample = 144;
 
 	uint64_t targetClock = GetTargetClock();
 
 	while(_clockCounter < targetClock) {
 		_clockCounter++;
 		_opn.Exec();
 
-		if((_clockCounter & (clocksPerSample - 1)) == 0) {
+		if(++_sampleClockCounter == clocksPerSample) {
 			_opn.GenerateSamples(_samples);
+			_sampleClockCounter = 0;
 		}
 	}
 }
@@ -101,6 +102,7 @@ void Epsm::Serialize(Serializer& s)
 	SV(_addr);
 	SV(_data);
 	SV(_masterClockRate);
+	SV(_sampleClockCounter);
 
 	SV(_opn);
 }
diff --git a/Core/NES/Epsm.h b/Core/NES/Epsm.h
@@ -21,6 +21,7 @@ class Epsm : public IAudioProvider, public INesMemoryHandler, public ISerializab
 
 	uint64_t _masterClockRate = 0;
 	uint64_t _clockCounter = 0;
+	uint8_t _sampleClockCounter = 0;
 	uint8_t _prevValue = 0;
 	uint8_t _data = 0;
 	uint8_t _addr = 0;

diff --git a/Core/NES/OpnInterface.h b/Core/NES/OpnInterface.h
@@ -26,6 +26,7 @@ class OpnInterface : public ymfm::ymfm_interface, public ISerializable
 		_adpcmRom.resize(0x2000);
 
 		_console = console;
+		_opn.set_fidelity(ymfm::OPN_FIDELITY_MED);
 		_opn.reset();
 	}