gverb.h

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/*
 
        Copyright (C) 1999 Juhana Sadeharju
                       kouhia at nic.funet.fi
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.
 
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 
    */
 
#ifndef GVERB_H
#define GVERB_H
 
#include <stdlib.h>
#include <math.h>
#include <string.h>
#include "gverbdsp.h"
#include "../ladspa-util.h"
 
#define FDNORDER 4
 
typedef struct {
  int rate;
  float inputbandwidth;
  float taillevel;
  float earlylevel;
  ty_damper *inputdamper;
  float maxroomsize;
  float roomsize;
  float revtime;
  float maxdelay;
  float largestdelay;
  ty_fixeddelay **fdndels;
  float *fdngains;
  int *fdnlens;
  ty_damper **fdndamps; 
  float fdndamping;
  ty_diffuser **ldifs;
  ty_diffuser **rdifs;
  ty_fixeddelay *tapdelay;
  int *taps;
  float *tapgains;
  float *d;
  float *u;
  float *f;
  double alpha;
} ty_gverb;
 
 
ty_gverb *gverb_new(int, float, float, float, float, float, float, float, float);
void gverb_free(ty_gverb *);
void gverb_flush(ty_gverb *);
static void gverb_do(ty_gverb *, float, float *, float *);
static void gverb_set_roomsize(ty_gverb *, float);
static void gverb_set_revtime(ty_gverb *, float);
static void gverb_set_damping(ty_gverb *, float);
static void gverb_set_inputbandwidth(ty_gverb *, float);
static void gverb_set_earlylevel(ty_gverb *, float);
static void gverb_set_taillevel(ty_gverb *, float);
 
/*
 * This FDN reverb can be made smoother by setting matrix elements at the
 * diagonal and near of it to zero or nearly zero. By setting diagonals to zero
 * means we remove the effect of the parallel comb structure from the
 * reverberation.  A comb generates uniform impulse stream to the reverberation
 * impulse response, and thus it is not good. By setting near diagonal elements
 * to zero means we remove delay sequences having consequtive delays of the
 * similar lenths, when the delays are in sorted in length with respect to
 * matrix element index. The matrix described here could be generated by
 * differencing Rocchesso's circulant matrix at max diffuse value and at low
 * diffuse value (approaching parallel combs).
 *
 * Example 1:
 * Set a(k,k), for all k, equal to 0.
 *
 * Example 2:
 * Set a(k,k), a(k,k-1) and a(k,k+1) equal to 0.
 *
 * Example 3: The transition to zero gains could be smooth as well.
 * a(k,k-1) and a(k,k+1) could be 0.3, and a(k,k-2) and a(k,k+2) could
 * be 0.5, say.
 */
 
static inline void gverb_fdnmatrix(float *a, float *b)
{
  const float dl0 = a[0], dl1 = a[1], dl2 = a[2], dl3 = a[3];
 
  b[0] = 0.5f*(+dl0 + dl1 - dl2 - dl3);
  b[1] = 0.5f*(+dl0 - dl1 - dl2 + dl3);
  b[2] = 0.5f*(-dl0 + dl1 - dl2 + dl3);
  b[3] = 0.5f*(+dl0 + dl1 + dl2 + dl3);
}
 
static inline void gverb_do(ty_gverb *p, float x, float *yl, float *yr)
{
  float z;
  unsigned int i;
  float lsum,rsum,sum,sign;
 
  if (isnan(x) || fabsf(x) > 100000.0f) {
    x = 0.0f;
  }
 
  z = damper_do(p->inputdamper, x);
 
  z = diffuser_do(p->ldifs[0],z);
 
  for(i = 0; i < FDNORDER; i++) {
    p->u[i] = p->tapgains[i]*fixeddelay_read(p->tapdelay,p->taps[i]);
  }
  fixeddelay_write(p->tapdelay,z);
 
  for(i = 0; i < FDNORDER; i++) {
    p->d[i] = damper_do(p->fdndamps[i],
                        p->fdngains[i]*fixeddelay_read(p->fdndels[i],
                                                       p->fdnlens[i]));
  }
 
  sum = 0.0f;
  sign = 1.0f;
  for(i = 0; i < FDNORDER; i++) {
    sum += sign*(p->taillevel*p->d[i] + p->earlylevel*p->u[i]);
    sign = -sign;
  }
  sum += x*p->earlylevel;
  lsum = sum;
  rsum = sum;
 
  gverb_fdnmatrix(p->d,p->f);
 
  for(i = 0; i < FDNORDER; i++) {
    fixeddelay_write(p->fdndels[i],p->u[i]+p->f[i]);
  }
 
  lsum = diffuser_do(p->ldifs[1],lsum);
  lsum = diffuser_do(p->ldifs[2],lsum);
  lsum = diffuser_do(p->ldifs[3],lsum);
  rsum = diffuser_do(p->rdifs[1],rsum);
  rsum = diffuser_do(p->rdifs[2],rsum);
  rsum = diffuser_do(p->rdifs[3],rsum);
 
  *yl = lsum;
  *yr = rsum;
}
 
static inline void gverb_set_roomsize(ty_gverb *p, const float a)
{
  unsigned int i;
 
  if (a <= 1.0 || isnan(a)) {
    p->roomsize = 1.0;
  } else {
    p->roomsize = a;
  }
  p->largestdelay = p->rate * p->roomsize * 0.00294f;
 
  p->fdnlens[0] = f_round(1.000000f*p->largestdelay);
  p->fdnlens[1] = f_round(0.816490f*p->largestdelay);
  p->fdnlens[2] = f_round(0.707100f*p->largestdelay);
  p->fdnlens[3] = f_round(0.632450f*p->largestdelay);
  for(i = 0; i < FDNORDER; i++) {
    p->fdngains[i] = -powf((float)p->alpha, p->fdnlens[i]);
  }
 
  p->taps[0] = 5+f_round(0.410f*p->largestdelay);
  p->taps[1] = 5+f_round(0.300f*p->largestdelay);
  p->taps[2] = 5+f_round(0.155f*p->largestdelay);
  p->taps[3] = 5+f_round(0.000f*p->largestdelay);
 
  for(i = 0; i < FDNORDER; i++) {
    p->tapgains[i] = powf((float)p->alpha, p->taps[i]);
  }
 
}
 
static inline void gverb_set_revtime(ty_gverb *p,float a)
{
  float ga,gt;
  double n;
  unsigned int i;
 
  p->revtime = a;
 
  ga = 60.0;
  gt = p->revtime;
  ga = powf(10.0f,-ga/20.0f);
  n = p->rate*gt;
  p->alpha = (double)powf(ga,1.0f/n);
 
  for(i = 0; i < FDNORDER; i++) {
    p->fdngains[i] = -powf((float)p->alpha, p->fdnlens[i]);
  }
 
}
 
static inline void gverb_set_damping(ty_gverb *p,float a)
{
  unsigned int i;
 
  p->fdndamping = a;
  for(i = 0; i < FDNORDER; i++) {
    damper_set(p->fdndamps[i],p->fdndamping);
  }
}
 
static inline void gverb_set_inputbandwidth(ty_gverb *p,float a)
{
  p->inputbandwidth = a;
  damper_set(p->inputdamper,1.0 - p->inputbandwidth);
}
 
static inline void gverb_set_earlylevel(ty_gverb *p,float a)
{
  p->earlylevel = a;
}
 
static inline void gverb_set_taillevel(ty_gverb *p,float a)
{
  p->taillevel = a;
}
 
#endif