mvcf~.c

/*
 * m0og vcf, 4-pole lowpass resonant filter
 * Copyright (c) 2005-2023 Edward Kelly
 * Forinformaion on usage and distribution, and for a DICLAIMER OF ALL
 * WARRANTIES, see the file "LICENSE.txt," in this distribution. */

#include "m_pd.h"
#include <math.h>
#define _limit 0.95

static t_class *mvcf_tilde_class;

typedef struct _mvcf_tilde {
  t_object x_obj;
  t_float b0, b1, b2, b3, b4;  //filter buffers to keep (beware denormals!)
  t_float token, debug, safety, mode;
  t_outlet *lp;
} t_mvcf_tilde;

/* We could have a mode where the fc and res are only registered at the start of the block (quick) or are registered in signal mode (slow) - i.e. a flag */

static inline t_float saturate( t_float input ) { //clamp without branching
  t_float x1 = fabsf( input + _limit );
  t_float x2 = fabsf( input - _limit );
  return 0.5 * (x1 - x2);
}


t_int *mvcf_tilde_perform(t_int *w) {
  t_mvcf_tilde   *x =   (t_mvcf_tilde *)(w[1]);
  t_sample      *in =       (t_sample *)(w[2]);
  t_sample      *fc =       (t_sample *)(w[3]);
  t_sample     *res =       (t_sample *)(w[4]);
  t_sample     *out =       (t_sample *)(w[5]);
  int             n =              (int)(w[6]);

  t_float t1 = 0;
  t_float t2 = 0;
  t_float xb0 = x->b0;
  t_float xb1 = x->b1;
  t_float xb2 = x->b2;
  t_float xb3 = x->b3;
  t_float xb4 = x->b4;
  t_float i1 = 0;
  t_float fc1 = 0;
  t_float res1 = 0;
  t_float q = 0;
  t_float p = 0;
  t_float fcoeff = 0;

  //  while (n-=4) {
  while (n--) {
    i1=(*in++);
    fc1 = (*fc++);
    /* This failsafe line stops the filter bursting
     * ...but it is expensive! */
    if(x->safety) {
      fc1 = fc1 <= 1 ? fc1 >= 0 ? fc1 : 0 : 1;
    }
    res1 = (*res++);
    q = 1.0f - fc1;
    p = fc1 + 0.8f * fc1 * q;
    fcoeff = p + p - 1.0f;
    q = res1 * (1.0f + 0.5f * q * (1.0f - q + 5.6f * q * q));
    i1 -= q * xb4;                          //feedback
    t1 = xb1;
    xb1 = (i1 + xb0) * p - xb1 * fcoeff;
    t2 = xb2;
    xb2 = (xb1 + t1) * p - xb2 * fcoeff;
    t1 = xb3;
    xb3 = (xb2 + t2) * p - xb3 * fcoeff;
    xb4 = (xb3 + t1) * p - xb4 * fcoeff;
    xb4 = saturate(xb4);
    xb4 = xb4 - xb4 * xb4 * xb4 * 0.01f;
    xb0 = i1;
    if(x->mode == 0) {
      *out++ = xb4; // lowpass mode
    } else if (x->mode == 1) {
      *out++ = i1 - x->b4; // highpass mode
    } else if (x->mode == 2) {
      *out++ = xb3 - xb4;
    }
    // Lowpass  output:  xb4
    // Highpass output:  in - xb4;
    // Bandpass output:  3.0f * (b3 - xb4);

  }
  x->b0 = xb0;
  x->b1 = xb1;
  x->b2 = xb2;
  x->b3 = xb3;
  x->b4 = xb4;
  //  if(x->debug != 0) {
  //    x->token +=1;
  //    if(x->token == 15) {
  //      post("q = %f, p=%f, fcoeff=%f, b0=%f, b1=%f, b2=%f, b3=%f, b4=%f",q,p,fcoeff,xb0,xb1,xb2,xb3,xb4);
  //      x->token = 0;
  //    }
  //  }
  return (w+7);
}

void mvcf_tilde_dsp(t_mvcf_tilde *x, t_signal **sp) {
  dsp_add(mvcf_tilde_perform, 6, x, sp[0]->s_vec, sp[1]->s_vec, sp[2]->s_vec, sp[3]->s_vec, sp[0]->s_n);
}

void mvcf_tilde_safety(t_mvcf_tilde *x, t_floatarg f) {
  x->safety = f != 0 ? 1 : 0;
}

void mvcf_tilde_mode(t_mvcf_tilde *x, t_floatarg f) {
  x->mode = f < 1 ? 0 : f > 1 ? 2 : 1;
}


void mvcf_tilde_clear(t_mvcf_tilde *x) {
  x->b0 = 0;
  x->b1 = 0;
  x->b2 = 0;
  x->b3 = 0;
  x->b4 = 0;
}

void mvcf_tilde_debug(t_mvcf_tilde *x, t_floatarg f) {
  x->debug = f != 0 ? 1 : 0;
}

void *mvcf_tilde_new(t_floatarg f) {
  t_mvcf_tilde *x = (t_mvcf_tilde *)pd_new(mvcf_tilde_class);

  x->b0 = 0;
  x->b1 = 0;
  x->b2 = 0;
  x->b3 = 0;
  x->b4 = 0;
  x->token = 0;
  x->safety = 0;

  inlet_new (&x->x_obj, &x->x_obj.ob_pd, &s_signal, &s_signal);
  inlet_new (&x->x_obj, &x->x_obj.ob_pd, &s_signal, &s_signal);
  outlet_new(&x->x_obj, &s_signal);
  return (void *)x;
}

void mvcf_tilde_setup(void) {
  mvcf_tilde_class = class_new(gensym("mvcf~"),
                               (t_newmethod)mvcf_tilde_new,
                               0, sizeof(t_mvcf_tilde),
                               CLASS_DEFAULT, A_DEFFLOAT, 0);

  post("~~~~~~~~~~~~~~~>mvcf~");
  post("~~~>by Ed Kelly, 2012");

  class_addmethod(mvcf_tilde_class,
                  (t_method)mvcf_tilde_dsp, gensym("dsp"), 0);
  CLASS_MAINSIGNALIN(mvcf_tilde_class, t_mvcf_tilde, token);
  class_addmethod(mvcf_tilde_class, (t_method)mvcf_tilde_clear, gensym("clear"), 0);
  class_addmethod(mvcf_tilde_class, (t_method)mvcf_tilde_debug, gensym("debug"), 0);
  class_addmethod(mvcf_tilde_class, (t_method)mvcf_tilde_safety, gensym("safe"), 0);
  class_addmethod(mvcf_tilde_class, (t_method)mvcf_tilde_mode, gensym("mode"), A_DEFFLOAT, 0);
}