mirror of https://github.com/xemu-project/xemu.git
92 lines
2.3 KiB
C
92 lines
2.3 KiB
C
/*
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* Adapted from SWH LADSPA Plugins package, modified for xemu
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*
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* Source: https://github.com/swh/ladspa/blob/master/svf_1214.xml
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* Author: Steve Harris, andy@vellocet
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* License: GPLv2
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*
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*/
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#ifndef SVF_H
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#define SVF_H
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#include <math.h>
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#define flush_to_zero(x) x
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// Constants to match filter types
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#define F_LP 1
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#define F_HP 2
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#define F_BP 3
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#define F_BR 4
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#define F_AP 5
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// Number of filter oversamples
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#define F_R 1
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/* Structure to hold parameters for SV filter */
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typedef struct {
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float f; // 2.0*sin(PI*fs/(fc*r));
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float q; // 2.0*cos(pow(q, 0.1)*PI*0.5);
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float qnrm; // sqrt(m/2.0f+0.01f);
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float h; // high pass output
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float b; // band pass output
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float l; // low pass output
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float p; // peaking output (allpass with resonance)
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float n; // notch output
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float *op; // pointer to output value
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} sv_filter;
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/* Store data in SVF struct, takes the sampling frequency, cutoff frequency
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and Q, and fills in the structure passed */
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/*
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static inline void setup_svf(sv_filter *sv, float fs, float fc, float q, int t) {
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sv->f = 2.0f * sin(M_PI * fc / (float)(fs * F_R));
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sv->q = 2.0f * cos(pow(q, 0.1f) * M_PI * 0.5f);
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*/
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static inline void setup_svf(sv_filter *sv, float fc, float q, int t) {
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sv->f = fc;
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sv->q = q;
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sv->qnrm = sqrt(sv->q/2.0+0.01);
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switch(t) {
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case F_LP:
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sv->op = &(sv->l);
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break;
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case F_HP:
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sv->op = &(sv->h);
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break;
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case F_BP:
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sv->op = &(sv->b);
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break;
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case F_BR:
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sv->op = &(sv->n);
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break;
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default:
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sv->op = &(sv->p);
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}
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}
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/* Run one sample through the SV filter. Filter is by andy@vellocet */
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static inline float run_svf(sv_filter *sv, float in) {
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float out;
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int i;
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in = sv->qnrm * in ;
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for (i=0; i < F_R; i++) {
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// very slight waveshape for extra stability
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sv->b = flush_to_zero(sv->b - sv->b * sv->b * sv->b * 0.001f);
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// regular state variable code here
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// the notch and peaking outputs are optional
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sv->h = flush_to_zero(in - sv->l - sv->q * sv->b);
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sv->b = sv->b + sv->f * sv->h;
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sv->l = flush_to_zero(sv->l + sv->f * sv->b);
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sv->n = sv->l + sv->h;
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sv->p = sv->l - sv->h;
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out = *(sv->op);
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in = out;
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}
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return out;
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}
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#endif
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