85 lines
2.4 KiB
C++
85 lines
2.4 KiB
C++
/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */
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/*
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Rubber Band Library
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An audio time-stretching and pitch-shifting library.
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Copyright 2007-2024 Particular Programs Ltd.
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version. See the file
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COPYING included with this distribution for more information.
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Alternatively, if you have a valid commercial licence for the
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Rubber Band Library obtained by agreement with the copyright
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holders, you may redistribute and/or modify it under the terms
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described in that licence.
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If you wish to distribute code using the Rubber Band Library
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under terms other than those of the GNU General Public License,
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you must obtain a valid commercial licence before doing so.
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*/
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#include "mathmisc.h"
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namespace RubberBand {
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void pickNearestRational(double ratio, int max_denom, int &num, int &denom)
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{
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// Farey algorithm, see
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// https://www.johndcook.com/blog/2010/10/20/best-rational-approximation/
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double a = 0.0, b = 1.0, c = 1.0, d = 0.0;
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double pa = a, pb = b, pc = c, pd = d;
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double eps = 1e-9;
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while (b <= max_denom && d <= max_denom) {
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double mediant = (a + c) / (b + d);
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if (fabs(ratio - mediant) < eps) {
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if (b + d <= max_denom) {
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num = a + c;
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denom = b + d;
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return;
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} else if (d > b) {
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num = c;
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denom = d;
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return;
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} else {
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num = a;
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denom = b;
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return;
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}
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}
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if (ratio > mediant) {
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pa = a; pb = b;
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a += c; b += d;
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} else {
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pc = c; pd = d;
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c += a; d += b;
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}
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}
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if (fabs(ratio - (pc / pd)) < fabs(ratio - (pa / pb))) {
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num = pc;
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denom = pd;
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} else {
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num = pa;
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denom = pb;
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}
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}
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size_t roundUp(size_t value)
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{
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if (!(value & (value - 1))) return value;
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size_t bits = 0;
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while (value) { ++bits; value >>= 1; }
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value = size_t(1) << bits;
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return value;
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}
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size_t roundUpDiv(double divisionOf, size_t divisor)
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{
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if (divisionOf < 0.0) return 0;
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return roundUp(size_t(ceil(divisionOf / double(divisor))));
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}
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}
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