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87 lines
2.7 KiB
C++
87 lines
2.7 KiB
C++
/**
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* Furnace Tracker - multi-system chiptune tracker
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* Copyright (C) 2021-2022 tildearrow and contributors
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#define _USE_MATH_DEFINES
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#include <math.h>
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#include "filter.h"
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#include "../ta-log.h"
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float* DivFilterTables::cubicTable=NULL;
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float* DivFilterTables::sincTable=NULL;
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float* DivFilterTables::sincIntegralTable=NULL;
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// portions from Schism Tracker (scripts/lutgen.c)
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// licensed under same license as this program.
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float* DivFilterTables::getCubicTable() {
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if (cubicTable==NULL) {
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logD("initializing cubic spline table.");
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cubicTable=new float[4096];
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for (int i=0; i<1024; i++) {
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float x=(float)i/1024.0;
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cubicTable[(i<<2)]=-0.5*pow(x,3)+1.0*pow(x,2)-0.5*x;
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cubicTable[1+(i<<2)]=1.5*pow(x,3)-2.5*pow(x,2)+1.0;
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cubicTable[2+(i<<2)]=-1.5*pow(x,3)+2.0*pow(x,2)+0.5*x;
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cubicTable[3+(i<<2)]=0.5*pow(x,3)-0.5*pow(x,2);
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}
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}
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return cubicTable;
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}
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float* DivFilterTables:: getSincTable() {
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if (sincTable==NULL) {
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logD("initializing sinc table.");
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sincTable=new float[65536];
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sincTable[0]=1.0f;
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for (int i=1; i<65536; i++) {
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int mapped=((i&8191)<<3)|(i>>13);
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double x=(double)i*M_PI/8192.0;
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sincTable[mapped]=sin(x)/x;
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}
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for (int i=0; i<65536; i++) {
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int mapped=((i&8191)<<3)|(i>>13);
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sincTable[mapped]*=pow(cos(M_PI*(double)i/131072.0),2.0);
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}
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}
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return sincTable;
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}
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float* DivFilterTables::getSincIntegralTable() {
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if (sincIntegralTable==NULL) {
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logD("initializing sinc integral table.");
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sincIntegralTable=new float[65536];
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sincIntegralTable[0]=-0.5f;
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for (int i=1; i<65536; i++) {
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int mapped=((i&8191)<<3)|(i>>13);
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int mappedPrev=(((i-1)&8191)<<3)|((i-1)>>13);
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double x=(double)i*M_PI/8192.0;
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double sinc=sin(x)/x;
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sincIntegralTable[mapped]=sincIntegralTable[mappedPrev]+(sinc/8192.0);
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}
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for (int i=0; i<65536; i++) {
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int mapped=((i&8191)<<3)|(i>>13);
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sincIntegralTable[mapped]*=pow(cos(M_PI*(double)i/131072.0),2.0);
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}
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}
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return sincIntegralTable;
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}
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