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