blender/intern/audaspace/FX/AUD_HighpassCalculator.cpp

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#include "AUD_HighpassCalculator.h"
#include <cmath>
#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif
AUD_HighpassCalculator::AUD_HighpassCalculator(float frequency, float Q) :
m_frequency(frequency),
m_Q(Q)
{
}
void AUD_HighpassCalculator::recalculateCoefficients(AUD_SampleRate rate, std::vector<float> &b, std::vector<float> &a)
{
float w0 = 2.0 * M_PI * (AUD_SampleRate)m_frequency / rate;
float alpha = (float)(sin(w0) / (2.0 * (double)m_Q));
float norm = 1 + alpha;
float c = cos(w0);
a.push_back(1);
a.push_back(-2 * c / norm);
a.push_back((1 - alpha) / norm);
b.push_back((1 + c) / (2 * norm));
b.push_back((-1 - c) / norm);
b.push_back(b[0]);
}