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#include "engine/filters/enginefilterbessel8.h"
#include "util/math.h"
EngineFilterBessel8Low::EngineFilterBessel8Low(int sampleRate,
double freqCorner1) {
setFrequencyCorners(sampleRate, freqCorner1);
}
void EngineFilterBessel8Low::setFrequencyCorners(int sampleRate,
double freqCorner1) {
// Copy the old coefficients into m_oldCoef
setCoefs("LpBe8", sampleRate, freqCorner1);
}
int EngineFilterBessel8Low::setFrequencyCornersForIntDelay(
double desiredCorner1Ratio, int maxDelay) {
// these values are calculated using the phase returned by
// fid_response_pha() at corner / 20
// group delay at 1 Hz freqCorner1 and 1 Hz Samplerate
const double kDelayFactor1 = 0.506051799;
// Factor, required to hit the end of the quadratic curve
const double kDelayFactor2 = 1.661247;
// Table for the non quadratic, high part near the sample rate
const double delayRatioTable[] = {
0.500000000, // delay 0
0.321399282, // delay 1
0.213843537, // delay 2
0.155141284, // delay 3
0.120432232, // delay 4
0.097999886, // delay 5
0.082451739, // delay 6
0.071098408, // delay 7
0.062444910, // delay 8
0.055665936, // delay 9
0.050197933, // delay 10
0.045689120, // delay 11
0.041927420, // delay 12
0.038735202, // delay 13
0.035992756, // delay 14
0.033611618, // delay 15
0.031525020, // delay 16
0.029681641, // delay 17
0.028041409, // delay 18
0.026572562, // delay 19
};
double dDelay = kDelayFactor1 / desiredCorner1Ratio - kDelayFactor2 * desiredCorner1Ratio;
int iDelay = math_clamp((int)(dDelay + 0.5), 0, maxDelay);
double quantizedRatio;
if (iDelay >= (int)(sizeof(delayRatioTable) / sizeof(double))) {
// pq formula, only valid for low frequencies
quantizedRatio = (-(iDelay / kDelayFactor2 / 2)) +
sqrt((iDelay / kDelayFactor2 / 2)*(iDelay / kDelayFactor2 / 2)
+ kDelayFactor1 / kDelayFactor2);
} else {
quantizedRatio = delayRatioTable[iDelay];
}
setCoefs("LpBe8", 1, quantizedRatio);
return iDelay;
}
EngineFilterBessel8Band::EngineFilterBessel8Band(int sampleRate,
double freqCorner1,
double freqCorner2) {
setFrequencyCorners(sampleRate, freqCorner1, freqCorner2);
}
void EngineFilterBessel8Band::setFrequencyCorners(int sampleRate,
double freqCorner1,
double freqCorner2) {
setCoefs("BpBe8", sampleRate, freqCorner1, freqCorner2);
}
EngineFilterBessel8High::EngineFilterBessel8High(int sampleRate,
double freqCorner1) {
setFrequencyCorners(sampleRate, freqCorner1);
}
void EngineFilterBessel8High::setFrequencyCorners(int sampleRate,
double freqCorner1) {
setCoefs("HpBe8", sampleRate, freqCorner1);
}
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