ft2-clone

commit cbfbcc413d629aa99bdf7f1f1b6b7b67a569e095
parent 65ae4b974e929be2bf6340739a17e9c9dcf70d67
Author: Olav Sørensen <olav.sorensen@live.no>
Date:   Fri, 23 Feb 2024 17:28:15 +0100

Cubic spline code cleanup

Diffstat:
M
src/mixer/ft2_cubic_spline.c
 | 
10
+++++-----
M
src/mixer/ft2_cubic_spline.h
 | 
2
+-

2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/src/mixer/ft2_cubic_spline.c b/src/mixer/ft2_cubic_spline.c
@@ -18,13 +18,13 @@ bool calcCubicSplineTable(void)
 	float *fPtr = fCubicSplineLUT;
 	for (int32_t i = 0; i < CUBIC_SPLINE_PHASES; i++)
 	{
-		const double x  = i * (1.0 / CUBIC_SPLINE_PHASES); // x = i / CUBIC_SPLINE_PHASES
-		const double x2 = x * x;  // x^2
-		const double x3 = x2 * x; // x^3
+		const double x1 = i * (1.0 / (double)CUBIC_SPLINE_PHASES); // i / CUBIC_SPLINE_PHASES
+		const double x2 = x1 * x1; // x^2
+		const double x3 = x2 * x1; // x^3
 
-		*fPtr++ = (float)(-0.5 * x3 + 1.0 * x2 - 0.5 * x);
+		*fPtr++ = (float)(-0.5 * x3 + 1.0 * x2 - 0.5 * x1);
 		*fPtr++ = (float)( 1.5 * x3 - 2.5 * x2 + 1.0);
-		*fPtr++ = (float)(-1.5 * x3 + 2.0 * x2 + 0.5 * x);
+		*fPtr++ = (float)(-1.5 * x3 + 2.0 * x2 + 0.5 * x1);
 		*fPtr++ = (float)( 0.5 * x3 - 0.5 * x2);
 	}
 
diff --git a/src/mixer/ft2_cubic_spline.h b/src/mixer/ft2_cubic_spline.h
@@ -5,7 +5,7 @@
 #include "ft2_mix.h" // MIXER_FRAC_BITS
 
 #define CUBIC_SPLINE_TAPS 4
-#define CUBIC_WIDTH_BITS 2
+#define CUBIC_WIDTH_BITS 2 // log2(CUBIC_SPLINE_TAPS)
 
 // 8192 is a good compromise
 #define CUBIC_SPLINE_PHASES 8192