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/* flib - PD library for feature extraction
Copyright (C) 2005 Jamie Bullock
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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
/*Calculate the (non optimized) cross correlation of two signal vectors*/
#include "flib.h"
#define SQ(a) (a * a)
static t_class *cross_class;
typedef struct _cross {
t_object x_obj;
t_float f;
t_int delay;
} t_cross;
static t_int *cross_perform(t_int *w)
{
t_sample *x = (t_sample *)(w[1]);
t_sample *y = (t_sample *)(w[2]);
t_sample *out = (t_sample *)(w[3]);
t_int N = (t_int)(w[4]),
i, j, delay;
t_int maxdelay = (t_int)(w[5]);
t_float mx, my, sx, sy, sxy, denom, r;
if(maxdelay > N * .5){
maxdelay = N * .5;
post("cross~: invalid maxdelay, must be <= blocksize/2");
}
/* Calculate the mean of the two series x[], y[] */
mx = 0;
my = 0;
for (i=0;i<N;i++) {
mx += x[i];
my += y[i];
}
mx /= N;
my /= N;
/* Calculate the denominator */
sx = 0;
sy = 0;
for (i=0;i<N;i++) {
sx += (x[i] - mx) * (x[i] - mx);
sy += (y[i] - my) * (y[i] - my);
}
denom = sqrt(sx*sy);
/* Calculate the correlation series */
for (delay=-maxdelay;delay<maxdelay;delay++) {
sxy = 0;
for (i=0;i<N;i++) {
j = i + delay;
/* circular correlation */
while (j < 0)
j += N;
j %= N;
sxy += (x[i] - mx) * (y[j] - my);
/*
if (j < 0 || j >= N)
continue;
else
sxy += (x[i] - mx) * (y[j] - my);
*/
/* Or should it be (?)
if (j < 0 || j >= n)
sxy += (x[i] - mx) * (-my);
else
sxy += (x[i] - mx) * (y[j] - my);
*/
}
r = sxy / denom;
*out++ = r;
/* r is the correlation coefficient at "delay" */
}
return (w+6);
}
static void cross_dsp(t_cross *x, t_signal **sp)
{
dsp_add(cross_perform, 5,
sp[0]->s_vec, sp[1]->s_vec, sp[2]->s_vec, sp[0]->s_n, x->delay);
}
static void *cross_new(t_floatarg f)
{
t_cross *x = (t_cross *)pd_new(cross_class);
x->delay = (t_int)f;
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 cross_tilde_setup(void) {
cross_class = class_new(gensym("cross~"),
(t_newmethod)cross_new,
0, sizeof(t_cross),
CLASS_DEFAULT, A_DEFFLOAT, 0);
class_addmethod(cross_class,
(t_method)cross_dsp, gensym("dsp"), 0);
CLASS_MAINSIGNALIN(cross_class, t_cross,f);
class_sethelpsymbol(cross_class, gensym("help-flib"));
}
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