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demod_dtmf.c
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demod_dtmf.c
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/*
* demod_dtmf.c -- DTMF signalling demodulator/decoder
*
* Copyright (C) 1996
* Thomas Sailer (sailer@ife.ee.ethz.ch, hb9jnx@hb9w.che.eu)
*
* 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.
*/
/* ---------------------------------------------------------------------- */
#include "multimon.h"
#include "filter.h"
#include <math.h>
#include <string.h>
/* ---------------------------------------------------------------------- */
/*
*
* DTMF frequencies
*
* 1209 1336 1477 1633
* 697 1 2 3 A
* 770 4 5 6 B
* 852 7 8 9 C
* 941 * 0 # D
*
*/
#define SAMPLE_RATE 22050
#define BLOCKLEN (SAMPLE_RATE/100) /* 10ms blocks */
#define BLOCKNUM 4 /* must match numbers in multimon.h */
#define PHINC(x) ((x)*0x10000/SAMPLE_RATE)
static const char *dtmf_transl = "123A456B789C*0#D";
static const unsigned int dtmf_phinc[8] = {
PHINC(1209), PHINC(1336), PHINC(1477), PHINC(1633),
PHINC(697), PHINC(770), PHINC(852), PHINC(941)
};
/* ---------------------------------------------------------------------- */
static void dtmf_init(struct demod_state *s)
{
memset(&s->l1.dtmf, 0, sizeof(s->l1.dtmf));
}
/* ---------------------------------------------------------------------- */
static int find_max_idx(const float *f)
{
float en = 0;
int idx = -1, i;
for (i = 0; i < 4; i++)
if (f[i] > en) {
en = f[i];
idx = i;
}
if (idx < 0)
return -1;
en *= 0.1;
for (i = 0; i < 4; i++)
if (idx != i && f[i] > en)
return -1;
return idx;
}
/* ---------------------------------------------------------------------- */
static inline int process_block(struct demod_state *s)
{
float tote;
float totte[16];
int i, j;
tote = 0;
for (i = 0; i < BLOCKNUM; i++)
tote += s->l1.dtmf.energy[i];
for (i = 0; i < 16; i++) {
totte[i] = 0;
for (j = 0; j < BLOCKNUM; j++)
totte[i] += s->l1.dtmf.tenergy[j][i];
}
for (i = 0; i < 8; i++)
totte[i] = fsqr(totte[i]) + fsqr(totte[i+8]);
memmove(s->l1.dtmf.energy+1, s->l1.dtmf.energy,
sizeof(s->l1.dtmf.energy) - sizeof(s->l1.dtmf.energy[0]));
s->l1.dtmf.energy[0] = 0;
memmove(s->l1.dtmf.tenergy+1, s->l1.dtmf.tenergy,
sizeof(s->l1.dtmf.tenergy) - sizeof(s->l1.dtmf.tenergy[0]));
memset(s->l1.dtmf.tenergy, 0, sizeof(s->l1.dtmf.tenergy[0]));
tote *= (BLOCKNUM*BLOCKLEN*0.5); /* adjust for block lengths */
verbprintf(10, "DTMF: Energies: %8.5f %8.5f %8.5f %8.5f %8.5f %8.5f %8.5f %8.5f %8.5f\n",
tote, totte[0], totte[1], totte[2], totte[3], totte[4], totte[5], totte[6], totte[7]);
if ((i = find_max_idx(totte)) < 0)
return -1;
if ((j = find_max_idx(totte+4)) < 0)
return -1;
if ((tote * 0.4) > (totte[i] + totte[j+4]))
return -1;
if (totte[i]*3.0<totte[j+4])
return -1;
if (totte[j+4]*3.0<totte[i])
return -1;
return (i & 3) | ((j << 2) & 0xc);
}
/* ---------------------------------------------------------------------- */
static void dtmf_demod(struct demod_state *s, buffer_t buffer, int length)
{
float s_in;
int i;
for (; length > 0; length--, buffer.fbuffer++) {
s_in = *buffer.fbuffer;
s->l1.dtmf.energy[0] += fsqr(s_in);
for (i = 0; i < 8; i++) {
s->l1.dtmf.tenergy[0][i] += COS(s->l1.dtmf.ph[i]) * s_in;
s->l1.dtmf.tenergy[0][i+8] += SIN(s->l1.dtmf.ph[i]) * s_in;
s->l1.dtmf.ph[i] += dtmf_phinc[i];
}
if ((s->l1.dtmf.blkcount--) <= 0) {
s->l1.dtmf.blkcount = BLOCKLEN;
i = process_block(s);
if (i != s->l1.dtmf.lastch && i >= 0)
verbprintf(0, "DTMF: %c\n", dtmf_transl[i]);
s->l1.dtmf.lastch = i;
}
}
}
/* ---------------------------------------------------------------------- */
const struct demod_param demod_dtmf = {
"DTMF", true, SAMPLE_RATE, 0, dtmf_init, dtmf_demod, NULL
};
/* ---------------------------------------------------------------------- */