Added B-spline and Optimal interpolations to in_snsf, but I'll probably be changing this later.
Added B-spline and Optimal interpolations to in_snsf, but I'll probably be changing this later.

--- a/src/in_snsf/XSFConfig_SNSF.cpp
+++ b/src/in_snsf/XSFConfig_SNSF.cpp
@@ -96,6 +96,8 @@
 			// Resampler
 			SendMessageW(GetDlgItem(hwndDlg, idResampler), CB_ADDSTRING, 0, reinterpret_cast<LPARAM>(L"Linear Resampler"));
 			SendMessageW(GetDlgItem(hwndDlg, idResampler), CB_ADDSTRING, 0, reinterpret_cast<LPARAM>(L"Hermite Resampler"));
+			SendMessageW(GetDlgItem(hwndDlg, idResampler), CB_ADDSTRING, 0, reinterpret_cast<LPARAM>(L"Bspline Resampler"));
+			SendMessageW(GetDlgItem(hwndDlg, idResampler), CB_ADDSTRING, 0, reinterpret_cast<LPARAM>(L"Optimal Resampler"));
 			SendMessageW(GetDlgItem(hwndDlg, idResampler), CB_SETCURSEL, this->resampler, 0);
 			// Mutes
 			for (int x = 0, numMutes = this->mutes.size(); x < numMutes; ++x)

--- a/src/in_snsf/XSFPlayer_SNSF.cpp
+++ b/src/in_snsf/XSFPlayer_SNSF.cpp
@@ -24,6 +24,8 @@
 #include "snes9x/apu/apu.h"
 #include "snes9x/apu/linear_resampler.h"
 #include "snes9x/apu/hermite_resampler.h"
+#include "snes9x/apu/bspline_resampler.h"
+#include "snes9x/apu/optimal_resampler.h"
 #include "snes9x/memmap.h"
 
 class XSFPlayer_SNSF : public XSFPlayer
@@ -228,7 +230,11 @@
 
 	S9xInitAPU();
 	XSFConfig_SNSF *xSFConfig_SNSF = dynamic_cast<XSFConfig_SNSF *>(xSFConfig);
-	if (xSFConfig_SNSF->resampler)
+	if (xSFConfig_SNSF->resampler == 3)
+		S9xInitSound<OptimalResampler>(10, 0);
+	if (xSFConfig_SNSF->resampler == 2)
+		S9xInitSound<BsplineResampler>(10, 0);
+	else if (xSFConfig_SNSF->resampler == 1)
 		S9xInitSound<HermiteResampler>(10, 0);
 	else
 		S9xInitSound<LinearResampler>(10, 0);

--- a/src/in_snsf/snes9x/apu/apu.cpp
+++ b/src/in_snsf/snes9x/apu/apu.cpp
@@ -182,6 +182,8 @@
 //#include "display.h"
 #include "linear_resampler.h"
 #include "hermite_resampler.h"
+#include "bspline_resampler.h"
+#include "optimal_resampler.h"
 
 #define APU_DEFAULT_INPUT_RATE		32000
 #define APU_MINIMUM_SAMPLE_COUNT	512
@@ -475,6 +477,8 @@
 
 template bool S9xInitSound<LinearResampler>(int, int);
 template bool S9xInitSound<HermiteResampler>(int, int);
+template bool S9xInitSound<BsplineResampler>(int, int);
+template bool S9xInitSound<OptimalResampler>(int, int);
 
 void S9xSetSoundControl (uint8_t voice_switch)
 {

--- /dev/null
+++ b/src/in_snsf/snes9x/apu/bspline_resampler.h
@@ -1,1 +1,123 @@
+/* Simple resampler based on bsnes's ruby audio library */
 
+#ifndef __BSPLINE_RESAMPLER_H
+#define __BSPLINE_RESAMPLER_H
+
+#include <cmath>
+#include "resampler.h"
+
+#undef CLAMP
+#undef SHORT_CLAMP
+template<typename T1, typename T2> static inline T1 CLAMP(T1 x, T2 low, T2 high) { return x > high ? high : (x < low ? low : x); }
+template<typename T> static inline short SHORT_CLAMP(T n) { return static_cast<short>(CLAMP(n, -32768, 32767)); }
+
+class BsplineResampler : public Resampler
+{
+protected:
+	double r_step;
+	double r_frac;
+	int r_left[4], r_right[4];
+
+	double bspline(double x, double a, double b, double c, double d)
+	{
+		double ym1py1 = a + c;
+		double c0 = 1 / 6.0 * ym1py1 + 2 / 3.0 * b;
+		double c1 = 0.5 * (c - a);
+		double c2 = 0.5 * ym1py1 - b;
+		double c3 = 0.5 * (b - c) + 1 / 6.0 * (d - a);
+		return ((c3 * x + c2) * x + c1) * x + c0;
+	}
+
+public:
+	BsplineResampler(int num_samples) : Resampler(num_samples)
+	{
+		this->clear();
+	}
+
+	void time_ratio(double ratio)
+	{
+		this->r_step = ratio;
+		this->clear();
+	}
+
+	void clear()
+	{
+		ring_buffer::clear ();
+		this->r_frac = 1.0;
+		this->r_left[0] = this->r_left[1] = this->r_left[2] = this->r_left[3] = 0;
+		this->r_right[0] = this->r_right[1] = this->r_right[2] = this->r_right[3] = 0;
+	}
+
+	void read(short *data, int num_samples)
+	{
+		int i_position = this->start >> 1;
+		short *internal_buffer = reinterpret_cast<short *>(this->buffer);
+		int o_position = 0;
+		int consumed = 0;
+
+		while (o_position < num_samples && consumed < this->buffer_size)
+		{
+			int s_left = internal_buffer[i_position];
+			int s_right = internal_buffer[i_position + 1];
+			int max_samples = this->buffer_size >> 1;
+			const double margin_of_error = 1.0e-10;
+
+			if (std::abs(this->r_step - 1.0) < margin_of_error)
+			{
+				data[o_position] = static_cast<short>(s_left);
+				data[o_position + 1] = static_cast<short>(s_right);
+
+				o_position += 2;
+				i_position += 2;
+				if (i_position >= max_samples)
+					i_position -= max_samples;
+				consumed += 2;
+
+				continue;
+			}
+
+			while (this->r_frac <= 1.0 && o_position < num_samples)
+			{
+				data[o_position] = SHORT_CLAMP(bspline(this->r_frac, this->r_left[0], this->r_left[1], this->r_left[2], this->r_left[3]));
+				data[o_position + 1] = SHORT_CLAMP(bspline(this->r_frac, this->r_right[0], this->r_right[1], this->r_right[2], this->r_right[3]));
+
+				o_position += 2;
+
+				this->r_frac += this->r_step;
+			}
+
+			if (this->r_frac > 1.0)
+			{
+				this->r_left[0] = this->r_left[1];
+				this->r_left[1] = this->r_left[2];
+				this->r_left[2] = this->r_left[3];
+				this->r_left[3] = s_left;
+
+				this->r_right[0] = this->r_right[1];
+				this->r_right[1] = this->r_right[2];
+				this->r_right[2] = this->r_right[3];
+				this->r_right[3] = s_right;
+
+				this->r_frac -= 1.0;
+
+				i_position += 2;
+				if (i_position >= max_samples)
+					i_position -= max_samples;
+				consumed += 2;
+			}
+		}
+
+		this->size -= consumed << 1;
+		this->start += consumed << 1;
+		if (this->start >= this->buffer_size)
+			this->start -= this->buffer_size;
+	}
+
+	inline int avail()
+	{
+		return static_cast<int>(std::floor(((this->size >> 2) - this->r_frac) / this->r_step) * 2);
+	}
+};
+
+#endif /* __BSPLINE_RESAMPLER_H */
+

--- /dev/null
+++ b/src/in_snsf/snes9x/apu/optimal_resampler.h
@@ -1,1 +1,126 @@
+/* Simple resampler based on bsnes's ruby audio library */
 
+#ifndef __OPTIMAL_RESAMPLER_H
+#define __OPTIMAL_RESAMPLER_H
+
+#include <cmath>
+#include "resampler.h"
+
+#undef CLAMP
+#undef SHORT_CLAMP
+//template<typename T1, typename T2> static inline T1 CLAMP(T1 x, T2 low, T2 high) { return x > high ? high : (x < low ? low : x); }
+//template<typename T> static inline short SHORT_CLAMP(T n) { return static_cast<short>(CLAMP(n, -32768, 32767)); }
+
+class OptimalResampler : public Resampler
+{
+protected:
+	double r_step;
+	double r_frac;
+	int r_left[4], r_right[4];
+
+	double optimal(double x, double a, double b, double c, double d)
+	{
+		double z = x - 0.5;
+		double even1 = c + b, odd1 = c - b;
+		double even2 = d + a, odd2 = d - a;
+		double c0 = even1 * 0.46822774170144532 + even2 * 0.03177225758005808;
+		double c1 = odd1 * 0.55890365706150436 + odd2 * 0.14703258836343669;
+		double c2 = even1 * -0.250153411893796031 + even2 * 0.25015343462990891;
+		double c3 = odd1 * -0.49800710906733769 + odd2 * 0.16600005174304033;
+		double c4 = even1 * 0.00064264050033187 + even2 * -0.00064273459469381;
+		return (((c4 * z + c3) * z + c2) * z + c1) * z + c0;
+	}
+
+public:
+	OptimalResampler(int num_samples) : Resampler(num_samples)
+	{
+		this->clear();
+	}
+
+	void time_ratio(double ratio)
+	{
+		this->r_step = ratio;
+		this->clear();
+	}
+
+	void clear()
+	{
+		ring_buffer::clear ();
+		this->r_frac = 1.0;
+		this->r_left[0] = this->r_left[1] = this->r_left[2] = this->r_left[3] = 0;
+		this->r_right[0] = this->r_right[1] = this->r_right[2] = this->r_right[3] = 0;
+	}
+
+	void read(short *data, int num_samples)
+	{
+		int i_position = this->start >> 1;
+		short *internal_buffer = reinterpret_cast<short *>(this->buffer);
+		int o_position = 0;
+		int consumed = 0;
+
+		while (o_position < num_samples && consumed < this->buffer_size)
+		{
+			int s_left = internal_buffer[i_position];
+			int s_right = internal_buffer[i_position + 1];
+			int max_samples = this->buffer_size >> 1;
+			const double margin_of_error = 1.0e-10;
+
+			if (std::abs(this->r_step - 1.0) < margin_of_error)
+			{
+				data[o_position] = static_cast<short>(s_left);
+				data[o_position + 1] = static_cast<short>(s_right);
+
+				o_position += 2;
+				i_position += 2;
+				if (i_position >= max_samples)
+					i_position -= max_samples;
+				consumed += 2;
+
+				continue;
+			}
+
+			while (this->r_frac <= 1.0 && o_position < num_samples)
+			{
+				data[o_position] = SHORT_CLAMP(optimal(this->r_frac, this->r_left[0], this->r_left[1], this->r_left[2], this->r_left[3]));
+				data[o_position + 1] = SHORT_CLAMP(optimal(this->r_frac, this->r_right[0], this->r_right[1], this->r_right[2], this->r_right[3]));
+
+				o_position += 2;
+
+				this->r_frac += this->r_step;
+			}
+
+			if (this->r_frac > 1.0)
+			{
+				this->r_left[0] = this->r_left[1];
+				this->r_left[1] = this->r_left[2];
+				this->r_left[2] = this->r_left[3];
+				this->r_left[3] = s_left;
+
+				this->r_right[0] = this->r_right[1];
+				this->r_right[1] = this->r_right[2];
+				this->r_right[2] = this->r_right[3];
+				this->r_right[3] = s_right;
+
+				this->r_frac -= 1.0;
+
+				i_position += 2;
+				if (i_position >= max_samples)
+					i_position -= max_samples;
+				consumed += 2;
+			}
+		}
+
+		this->size -= consumed << 1;
+		this->start += consumed << 1;
+		if (this->start >= this->buffer_size)
+			this->start -= this->buffer_size;
+	}
+
+	inline int avail()
+	{
+		return static_cast<int>(std::floor(((this->size >> 2) - this->r_frac) / this->r_step) * 2);
+	}
+};
+
+#endif /* __OPTIMAL_RESAMPLER_H */
+