1 /* Copyright (C) 2010-2020 The RetroArch team
3 * ---------------------------------------------------------------------------------------
4 * The following license statement only applies to this file (filters.h).
5 * ---------------------------------------------------------------------------------------
7 * Permission is hereby granted, free of charge,
8 * to any person obtaining a copy of this software and associated documentation files (the "Software"),
9 * to deal in the Software without restriction, including without limitation the rights to
10 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software,
11 * and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
13 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
16 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
18 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
19 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
23 #ifndef _LIBRETRO_SDK_FILTERS_H
24 #define _LIBRETRO_SDK_FILTERS_H
26 /* for MSVC; should be benign under any circumstances */
27 #define _USE_MATH_DEFINES
31 #include <retro_inline.h>
32 #include <retro_math.h>
39 static INLINE double sinc(double val)
41 if (fabs(val) < 0.00001)
43 return sin(val) / val;
50 * Paeth prediction filter.
52 static INLINE int paeth(int a, int b, int c)
59 if (pa <= pb && pa <= pc)
71 * Modified Bessel function of first order.
72 * Check Wiki for mathematical definition ...
74 static INLINE double besseli0(double x)
78 double factorial = 1.0;
79 double factorial_mult = 0.0;
81 double two_div_pow = 1.0;
84 /* Approximate. This is an infinite sum.
85 * Luckily, it converges rather fast. */
86 for (i = 0; i < 18; i++)
88 sum += x_pow * two_div_pow / (factorial * factorial);
89 factorial_mult += 1.0;
92 factorial *= factorial_mult;
98 static INLINE double kaiser_window_function(double index, double beta)
100 return besseli0(beta * sqrtf(1 - index * index));