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109 lines
5.3 KiB
C
109 lines
5.3 KiB
C
/*
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* Based on the public domain version by Olivier Lapicque
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* Rewritten for libxmp by Claudio Matsuoka
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*
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* Copyright (C) 2012 Claudio Matsuoka
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#ifndef LIBXMP_CORE_DISABLE_IT
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#include <math.h>
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#include "xmp.h"
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#include "common.h"
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#include "mixer.h"
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/* LUT for 2 * damping factor */
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static const float resonance_table[128] = {
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1.0000000000000000f, 0.9786446094512940f, 0.9577452540397644f, 0.9372922182083130f,
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0.9172759056091309f, 0.8976871371269226f, 0.8785166740417481f, 0.8597555756568909f,
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0.8413951396942139f, 0.8234267830848694f, 0.8058421611785889f, 0.7886331081390381f,
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0.7717915177345276f, 0.7553095817565918f, 0.7391796708106995f, 0.7233941555023193f,
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0.7079457640647888f, 0.6928272843360901f, 0.6780316829681397f, 0.6635520458221436f,
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0.6493816375732422f, 0.6355138421058655f, 0.6219421625137329f, 0.6086603403091431f,
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0.5956621170043945f, 0.5829415321350098f, 0.5704925656318665f, 0.5583094954490662f,
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0.5463865399360657f, 0.5347182154655457f, 0.5232990980148315f, 0.5121238231658936f,
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0.5011872053146362f, 0.4904841780662537f, 0.4800096750259399f, 0.4697588682174683f,
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0.4597269892692566f, 0.4499093294143677f, 0.4403013288974762f, 0.4308985173702240f,
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0.4216965138912201f, 0.4126909971237183f, 0.4038778245449066f, 0.3952528536319733f,
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0.3868120610713959f, 0.3785515129566193f, 0.3704673945903778f, 0.3625559210777283f,
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0.3548133969306946f, 0.3472362160682678f, 0.3398208320140839f, 0.3325638175010681f,
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0.3254617750644684f, 0.3185114264488220f, 0.3117094635963440f, 0.3050527870655060f,
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0.2985382676124573f, 0.2921628654003143f, 0.2859236001968384f, 0.2798175811767578f,
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0.2738419771194458f, 0.2679939568042755f, 0.2622708380222321f, 0.2566699385643005f,
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0.2511886358261108f, 0.2458244115114212f, 0.2405747324228287f, 0.2354371547698975f,
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0.2304092943668366f, 0.2254888117313385f, 0.2206734120845795f, 0.2159608304500580f,
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0.2113489061594009f, 0.2068354636430740f, 0.2024184018373489f, 0.1980956792831421f,
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0.1938652694225311f, 0.1897251904010773f, 0.1856735348701477f, 0.1817083954811096f,
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0.1778279393911362f, 0.1740303486585617f, 0.1703138649463654f, 0.1666767448186874f,
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0.1631172895431519f, 0.1596338599920273f, 0.1562248021364212f, 0.1528885662555695f,
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0.1496235728263855f, 0.1464282870292664f, 0.1433012634515762f, 0.1402409970760346f,
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0.1372461020946503f, 0.1343151479959488f, 0.1314467936754227f, 0.1286396980285645f,
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0.1258925348520279f, 0.1232040524482727f, 0.1205729842185974f, 0.1179980933666229f,
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0.1154781952500343f, 0.1130121126770973f, 0.1105986908078194f, 0.1082368120551109f,
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0.1059253737330437f, 0.1036632955074310f, 0.1014495193958283f, 0.0992830246686935f,
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0.0971627980470657f, 0.0950878411531448f, 0.0930572077631950f, 0.0910699293017387f,
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0.0891250967979431f, 0.0872217938303947f, 0.0853591337800026f, 0.0835362523794174f,
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0.0817523002624512f, 0.0800064504146576f, 0.0782978758215904f, 0.0766257941722870f,
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0.0749894231557846f, 0.0733879879117012f, 0.0718207582831383f, 0.0702869966626167f,
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0.0687859877943993f, 0.0673170387744904f, 0.0658794566988945f, 0.0644725710153580f,
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};
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#if !defined(HAVE_POWF) || defined(__DJGPP__) || defined(__WATCOMC__)
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/* Watcom doesn't have powf. DJGPP have a C-only implementation in libm. */
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#undef powf
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#define powf(f1_,f2_) (float)pow((f1_),(f2_))
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#endif
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/*
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* Simple 2-poles resonant filter
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*/
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#define FREQ_PARAM_MULT (128.0f / (24.0f * 256.0f))
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void libxmp_filter_setup(int srate, int cutoff, int res, int *a0, int *b0, int *b1)
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{
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float fc, fs = (float)srate;
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float fg, fb0, fb1;
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float r, d, e;
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/* [0-255] => [100Hz-8000Hz] */
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CLAMP(cutoff, 0, 255);
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CLAMP(res, 0, 255);
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fc = 110.0f * powf(2.0f, (float)cutoff * FREQ_PARAM_MULT + 0.25f);
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if (fc > fs / 2.0f) {
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fc = fs / 2.0f;
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}
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r = fs / (2.0 * 3.14159265358979f * fc);
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d = resonance_table[res >> 1] * (r + 1.0) - 1.0;
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e = r * r;
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fg = 1.0 / (1.0 + d + e);
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fb0 = (d + e + e) / (1.0 + d + e);
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fb1 = -e / (1.0 + d + e);
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*a0 = (int)(fg * (1 << FILTER_SHIFT));
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*b0 = (int)(fb0 * (1 << FILTER_SHIFT));
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*b1 = (int)(fb1 * (1 << FILTER_SHIFT));
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}
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#endif
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