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Use extracted pickNearestRational; ensure the max rational is actually the max for both num and denom

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This commit is contained in:
Chris Cannam
2022-09-02 12:06:45 +01:00
parent a525654d6a
commit 2025c51d64
1 changed files with 7 additions and 28 deletions
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35
src/common/BQResampler.cpp
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@@ -31,6 +31,8 @@
#include "Allocators.h"
#include "VectorOps.h"
#include "mathmisc.h"
#define BQ_R__ R__
using std::vector;
@@ -376,41 +378,18 @@ BQResampler::fill_params(double ratio, double numd, double denomd) const
BQResampler::params
BQResampler::pick_params(double ratio) const
{
// Farey algorithm, see
// https://www.johndcook.com/blog/2010/10/20/best-rational-approximation/
int max_denom;
if (m_dynamism == RatioMostlyFixed) {
max_denom = 192000;
} else {
max_denom = m_qparams.rational_max;
}
double a = 0.0, b = 1.0, c = 1.0, d = 0.0;
double pa = a, pb = b, pc = c, pd = d;
double eps = 1e-9;
while (b <= max_denom && d <= max_denom) {
double mediant = (a + c) / (b + d);
if (fabs(ratio - mediant) < eps) {
if (b + d <= max_denom) {
return fill_params(ratio, a + c, b + d);
} else if (d > b) {
return fill_params(ratio, c, d);
} else {
return fill_params(ratio, a, b);
}
}
if (ratio > mediant) {
pa = a; pb = b;
a += c; b += d;
} else {
pc = c; pd = d;
c += a; d += b;
if (ratio > 1.0) {
max_denom = int(ceil(max_denom / ratio));
}
}
if (fabs(ratio - (pc / pd)) < fabs(ratio - (pa / pb))) {
return fill_params(ratio, pc, pd);
} else {
return fill_params(ratio, pa, pb);
}
int num, denom;
pickNearestRational(ratio, max_denom, num, denom);
return fill_params(ratio, num, denom);
}
void