Chris Robinson
127 lines
4.1 KiB
C++
127 lines
4.1 KiB
C++
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#include "config.h"
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#include "biquad.h"
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#include <algorithm>
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#include <cassert>
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#include <cmath>
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#include "opthelpers.h"
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template<typename Real>
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void BiquadFilterR<Real>::setParams(BiquadType type, Real gain, Real f0norm, Real rcpQ)
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{
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// Limit gain to -100dB
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assert(gain > 0.00001f);
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const Real w0{al::MathDefs<Real>::Tau() * f0norm};
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const Real sin_w0{std::sin(w0)};
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const Real cos_w0{std::cos(w0)};
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const Real alpha{sin_w0/2.0f * rcpQ};
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Real sqrtgain_alpha_2;
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Real a[3]{ 1.0f, 0.0f, 0.0f };
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Real b[3]{ 1.0f, 0.0f, 0.0f };
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/* Calculate filter coefficients depending on filter type */
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switch(type)
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{
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case BiquadType::HighShelf:
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sqrtgain_alpha_2 = 2.0f * std::sqrt(gain) * alpha;
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b[0] = gain*((gain+1.0f) + (gain-1.0f)*cos_w0 + sqrtgain_alpha_2);
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b[1] = -2.0f*gain*((gain-1.0f) + (gain+1.0f)*cos_w0 );
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b[2] = gain*((gain+1.0f) + (gain-1.0f)*cos_w0 - sqrtgain_alpha_2);
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a[0] = (gain+1.0f) - (gain-1.0f)*cos_w0 + sqrtgain_alpha_2;
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a[1] = 2.0f* ((gain-1.0f) - (gain+1.0f)*cos_w0 );
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a[2] = (gain+1.0f) - (gain-1.0f)*cos_w0 - sqrtgain_alpha_2;
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break;
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case BiquadType::LowShelf:
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sqrtgain_alpha_2 = 2.0f * std::sqrt(gain) * alpha;
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b[0] = gain*((gain+1.0f) - (gain-1.0f)*cos_w0 + sqrtgain_alpha_2);
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b[1] = 2.0f*gain*((gain-1.0f) - (gain+1.0f)*cos_w0 );
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b[2] = gain*((gain+1.0f) - (gain-1.0f)*cos_w0 - sqrtgain_alpha_2);
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a[0] = (gain+1.0f) + (gain-1.0f)*cos_w0 + sqrtgain_alpha_2;
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a[1] = -2.0f* ((gain-1.0f) + (gain+1.0f)*cos_w0 );
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a[2] = (gain+1.0f) + (gain-1.0f)*cos_w0 - sqrtgain_alpha_2;
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break;
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case BiquadType::Peaking:
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b[0] = 1.0f + alpha * gain;
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b[1] = -2.0f * cos_w0;
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b[2] = 1.0f - alpha * gain;
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a[0] = 1.0f + alpha / gain;
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a[1] = -2.0f * cos_w0;
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a[2] = 1.0f - alpha / gain;
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break;
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case BiquadType::LowPass:
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b[0] = (1.0f - cos_w0) / 2.0f;
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b[1] = 1.0f - cos_w0;
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b[2] = (1.0f - cos_w0) / 2.0f;
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a[0] = 1.0f + alpha;
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a[1] = -2.0f * cos_w0;
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a[2] = 1.0f - alpha;
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break;
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case BiquadType::HighPass:
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b[0] = (1.0f + cos_w0) / 2.0f;
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b[1] = -(1.0f + cos_w0);
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b[2] = (1.0f + cos_w0) / 2.0f;
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a[0] = 1.0f + alpha;
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a[1] = -2.0f * cos_w0;
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a[2] = 1.0f - alpha;
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break;
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case BiquadType::BandPass:
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b[0] = alpha;
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b[1] = 0.0f;
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b[2] = -alpha;
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a[0] = 1.0f + alpha;
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a[1] = -2.0f * cos_w0;
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a[2] = 1.0f - alpha;
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break;
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}
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mA1 = a[1] / a[0];
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mA2 = a[2] / a[0];
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mB0 = b[0] / a[0];
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mB1 = b[1] / a[0];
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mB2 = b[2] / a[0];
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}
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template<typename Real>
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void BiquadFilterR<Real>::process(Real *dst, const Real *src, const size_t numsamples)
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{
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ASSUME(numsamples > 0);
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const Real b0{mB0};
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const Real b1{mB1};
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const Real b2{mB2};
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const Real a1{mA1};
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const Real a2{mA2};
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Real z1{mZ1};
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Real z2{mZ2};
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/* Processing loop is Transposed Direct Form II. This requires less storage
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* compared to Direct Form I (only two delay components, instead of a four-
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* sample history; the last two inputs and outputs), and works better for
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* floating-point which favors summing similarly-sized values while being
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* less bothered by overflow.
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*
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* See: http://www.earlevel.com/main/2003/02/28/biquads/
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*/
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auto proc_sample = [b0,b1,b2,a1,a2,&z1,&z2](Real input) noexcept -> Real
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{
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Real output = input*b0 + z1;
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z1 = input*b1 - output*a1 + z2;
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z2 = input*b2 - output*a2;
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return output;
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};
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std::transform(src, src+numsamples, dst, proc_sample);
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mZ1 = z1;
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mZ2 = z2;
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}
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template class BiquadFilterR<float>;
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template class BiquadFilterR<double>;
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