source: src/temporal/filter.c @ 6481c0c

/*
   Copyright (C) 2003 Paul Brossier

   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.

*/


/* Requires lsmp_t to be long or double. float will NOT give reliable 
 * results */

#include "aubio_priv.h"
#include "fvec.h"
#include "lvec.h"
#include "mathutils.h"
#include "temporal/filter.h"

struct _aubio_filter_t {
  uint_t order;
  uint_t samplerate;
  lvec_t * a;
  lvec_t * b;
  lvec_t * y;
  lvec_t * x;
};

void aubio_filter_do_outplace(aubio_filter_t * f, fvec_t * in, fvec_t * out) {
  fvec_copy(in, out);
  aubio_filter_do (f, out);
}

void aubio_filter_do(aubio_filter_t * f, fvec_t * in) {
  uint_t i,j,l, order = f->order;
  lsmp_t *x;
  lsmp_t *y;
  lsmp_t *a = f->a->data[0];
  lsmp_t *b = f->b->data[0];

  for (i = 0; i < in->channels; i++) {
    x = f->x->data[i];
    y = f->y->data[i];
    for (j = 0; j < in->length; j++) {
      /* new input */
      x[0] = KILL_DENORMAL(in->data[i][j]);
      y[0] = b[0] * x[0];
      for (l=1;l<order; l++) {
        y[0] += b[l] * x[l];
        y[0] -= a[l] * y[l];
      }
      /* new output */
      in->data[i][j] = y[0];
      /* store for next sample */
      for (l=order-1; l>0; l--){
        x[l] = x[l-1];
        y[l] = y[l-1];
      }
    }
    /* store for next run */
    f->x->data[i] = x;
    f->y->data[i] = y;
  }
}

/*  
 *
 * despite mirroring, end effects destroy both phse and amplitude. the longer
 * the buffer, the less affected they are.
 *
 * replacing with zeros clicks.
 *
 * seems broken for order > 4 (see biquad_do_filtfilt for audible one) 
 */
void aubio_filter_do_filtfilt(aubio_filter_t * f, fvec_t * in, fvec_t * tmp) {
  uint_t j,i=0;
  uint_t length = in->length;
  //uint_t order = f->order;
  //lsmp_t mir;
  /* mirroring */
  //mir = 2*in->data[i][0];
  //for (j=1;j<order;j++)
  //f->x[j] = 0.;//mir - in->data[i][order-j];
  /* apply filtering */
  aubio_filter_do(f,in);
  /* invert */
  for (j = 0; j < length; j++)
    tmp->data[i][length-j-1] = in->data[i][j];
  /* mirror inverted */
  //mir = 2*tmp->data[i][0];
  //for (j=1;j<order;j++)
  //f->x[j] = 0.;//mir - tmp->data[i][order-j];
  /* apply filtering on inverted */
  aubio_filter_do(f,tmp);
  /* invert back */
  for (j = 0; j < length; j++)
    in->data[i][j] = tmp->data[i][length-j-1];
}

lvec_t * aubio_filter_get_feedback ( aubio_filter_t *f ) {
  return f->a;
}

lvec_t * aubio_filter_get_feedforward ( aubio_filter_t *f ) {
  return f->b;
}

uint_t aubio_filter_get_order ( aubio_filter_t *f ) {
  return f->order;
}

uint_t aubio_filter_get_samplerate ( aubio_filter_t *f ) {
  return f->samplerate;
}

aubio_filter_t * new_aubio_filter(uint_t samplerate, 
    uint_t order, uint_t channels) {
  aubio_filter_t * f = AUBIO_NEW(aubio_filter_t);
  f->x = new_lvec(order, channels);
  f->y = new_lvec(order, channels);
  f->a = new_lvec(order, 1);
  f->b = new_lvec(order, 1);
  f->samplerate = samplerate; 
  f->order = order;
  /* set default to identity */
  f->a->data[0][1] = 1.;
  return f;
}

void del_aubio_filter(aubio_filter_t * f) {
  del_lvec(f->a);
  del_lvec(f->b);
  del_lvec(f->x);
  del_lvec(f->y);
  AUBIO_FREE(f);
  return;
}