Chris Robinson
125 lines
4.2 KiB
C++
125 lines
4.2 KiB
C++
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#include "config.h"
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#include <cmath>
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#include "AL/alc.h"
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#include "AL/al.h"
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#include "alMain.h"
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#include "defs.h"
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void BiquadFilter_setParams(BiquadFilter *filter, BiquadType type, ALfloat gain, ALfloat f0norm, ALfloat rcpQ)
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{
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ALfloat alpha, sqrtgain_alpha_2;
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ALfloat w0, sin_w0, cos_w0;
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ALfloat a[3] = { 1.0f, 0.0f, 0.0f };
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ALfloat b[3] = { 1.0f, 0.0f, 0.0f };
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// Limit gain to -100dB
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assert(gain > 0.00001f);
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w0 = F_TAU * f0norm;
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sin_w0 = std::sin(w0);
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cos_w0 = std::cos(w0);
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alpha = sin_w0/2.0f * rcpQ;
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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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gain = std::sqrt(gain);
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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;
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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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filter->a1 = a[1] / a[0];
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filter->a2 = a[2] / a[0];
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filter->b0 = b[0] / a[0];
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filter->b1 = b[1] / a[0];
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filter->b2 = b[2] / a[0];
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}
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void BiquadFilter_processC(BiquadFilter *filter, ALfloat *RESTRICT dst, const ALfloat *RESTRICT src, ALsizei numsamples)
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{
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const ALfloat b0 = filter->b0;
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const ALfloat b1 = filter->b1;
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const ALfloat b2 = filter->b2;
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const ALfloat a1 = filter->a1;
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const ALfloat a2 = filter->a2;
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ALfloat z1 = filter->z1;
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ALfloat z2 = filter->z2;
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ASSUME(numsamples > 0);
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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](ALfloat input) noexcept -> ALfloat
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{
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ALfloat 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<const ALfloat*RESTRICT>(src, src+numsamples, dst, proc_sample);
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filter->z1 = z1;
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filter->z2 = z2;
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}
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