yeah

src/engine/platform/snes.cpp

@@ -841,6 +841,8 @@ void DivPlatformSNES::reset() {
   memcpy(sampleMem,copyOfSampleMem,65536);
   dsp.init(sampleMem);
   dsp.set_output(NULL,0);
+  dsp.setupInterpolation(interpolationOn);
+
   memset(regPool,0,128);
   // this can't be 0 or channel 1 won't play
   // this can't be 0x100 either as that's used by SPC700 page 1 and the stack
@@ -1023,6 +1025,8 @@ void DivPlatformSNES::setFlags(const DivConfig& flags) {
   initEchoFIR[7]=flags.getInt("echoFilter7",0);
 
   initEchoMask=flags.getInt("echoMask",0);
+
+  interpolationOn=flags.getBool("interpolationOn",true);
 }
 
 int DivPlatformSNES::init(DivEngine* p, int channels, int sugRate, const DivConfig& flags) {

src/engine/platform/snes.h

@@ -69,6 +69,7 @@ class DivPlatformSNES: public DivDispatch {
   bool writeEcho;
   bool writeDryVol;
   bool echoOn;
+  bool interpolationOn;
 
   bool initEchoOn;
   signed char initEchoVolL;

src/engine/platform/sound/snes/SPC_DSP.cpp

@@ -135,24 +135,39 @@ static short const gauss [512] =
 1299,1300,1300,1301,1302,1302,1303,1303,1303,1304,1304,1304,1304,1304,1305,1305,
 };
 
+void SPC_DSP::setupInterpolation(bool interpolate)
+{
+	for(int i = 0; i < voice_count; i++)
+	{
+		m.voices[i].interpolate = interpolate;
+	}
+}
+
 inline int SPC_DSP::interpolate( voice_t const* v )
 {
 	// Make pointers into gaussian based on fractional position between samples
-	int offset = v->interp_pos >> 4 & 0xFF;
+	if(v->interpolate)
-	short const* fwd = gauss + 255 - offset;
+	{
-	short const* rev = gauss       + offset; // mirror left half of gaussian
+		int offset = v->interp_pos >> 4 & 0xFF;
+		short const* fwd = gauss + 255 - offset;
+		short const* rev = gauss       + offset; // mirror left half of gaussian
 
-	int const* in = &v->buf [(v->interp_pos >> 12) + v->buf_pos];
+		int const* in = &v->buf [(v->interp_pos >> 12) + v->buf_pos];
-	int out;
+		int out;
-	out  = (fwd [  0] * in [0]) >> 11;
+		out  = (fwd [  0] * in [0]) >> 11;
-	out += (fwd [256] * in [1]) >> 11;
+		out += (fwd [256] * in [1]) >> 11;
-	out += (rev [256] * in [2]) >> 11;
+		out += (rev [256] * in [2]) >> 11;
-	out = (int16_t) out;
+		out = (int16_t) out;
-	out += (rev [  0] * in [3]) >> 11;
+		out += (rev [  0] * in [3]) >> 11;
 
-	CLAMP16( out );
+		CLAMP16( out );
-	out &= ~1;
+		out &= ~1;
-	return out;
+		return out;
+	}
+	else
+	{
+		return v->buf [(v->interp_pos >> 12) + v->buf_pos]; //Furnace addition -- no interpolation
+	}
 }
 
 

src/engine/platform/sound/snes/SPC_DSP.h

@@ -27,6 +27,9 @@ public:
 	// output buffer could hold.
 	int sample_count() const;
 
+	// Furnace addition: disable/enable Gaussian interpolation
+	void setupInterpolation(bool interpolate);
+
 // Emulation
 
 	// Resets DSP to power-on state
@@ -122,6 +125,7 @@ public:
 		int hidden_env;         // used by GAIN mode 7, very obscure quirk
 		uint8_t t_envx_out;
 		sample_t out[2];        // Furnace addition, for per-channel oscilloscope
+		bool interpolate;       // Furnace addition, to disable interpolation
 	};
 
   // Furnace addition, gets a voice

src/gui/sysConf.cpp

@@ -1969,6 +1969,8 @@ bool FurnaceGUI::drawSysConf(int chan, int sysPos, DivSystem type, DivConfig& fl
       echoFilter[6]=flags.getInt("echoFilter6",0);
       echoFilter[7]=flags.getInt("echoFilter7",0);
 
+      bool interpolationOn=flags.getBool("interpolationOn",true);
+
       ImGui::Text(_("Volume scale:"));
       if (CWSliderInt(_("Left##VolScaleL"),&vsL,0,127)) {
         if (vsL<0) vsL=0;
@@ -2084,6 +2086,10 @@ bool FurnaceGUI::drawSysConf(int chan, int sysPos, DivSystem type, DivConfig& fl
       ImGui::Text(_("sum: %d"),filterSum);
       ImGui::PopStyleColor();
 
+      if (ImGui::Checkbox(_("Gaussian interpolation"),&interpolationOn)) {
+        altered=true;
+      }
+
       if (altered) {
         e->lockSave([&]() {
           flags.set("volScaleL",127-vsL);
@@ -2102,6 +2108,7 @@ bool FurnaceGUI::drawSysConf(int chan, int sysPos, DivSystem type, DivConfig& fl
           flags.set("echoFilter6",echoFilter[6]);
           flags.set("echoFilter7",echoFilter[7]);
           flags.set("echoMask",echoMask);
+          flags.set("interpolationOn",interpolationOn);
         });
       }