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/*
* DTMF decoder.
*
* Copyright by Andreas Eversberg (jolly@eversberg.eu)
* based on different decoders such as ISDN4Linux
*
* This software may be used and distributed according to the terms
* of the GNU General Public License, incorporated herein by reference.
*
*/
#include <linux/mISDNif.h>
#include <linux/mISDNdsp.h>
#include "core.h"
#include "dsp.h"
#define NCOEFF 8 /* number of frequencies to be analyzed */
/* For DTMF recognition:
* 2 * cos(2 * PI * k / N) precalculated for all k
*/
static u64 cos2pik[NCOEFF] =
{
/* k << 15 (source: hfc-4s/8s documentation (www.colognechip.de)) */
55960, 53912, 51402, 48438, 38146, 32650, 26170, 18630
};
/* digit matrix */
static char dtmf_matrix[4][4] =
{
{'1', '2', '3', 'A'},
{'4', '5', '6', 'B'},
{'7', '8', '9', 'C'},
{'*', '0', '#', 'D'}
};
/* dtmf detection using goertzel algorithm
* init function
*/
void dsp_dtmf_goertzel_init(struct dsp *dsp)
{
dsp->dtmf.size = 0;
dsp->dtmf.lastwhat = '\0';
dsp->dtmf.lastdigit = '\0';
dsp->dtmf.count = 0;
}
/* check for hardware or software features
*/
void dsp_dtmf_hardware(struct dsp *dsp)
{
int hardware = 1;
if (!dsp->dtmf.enable)
return;
if (!dsp->features.hfc_dtmf)
hardware = 0;
/* check for volume change */
if (dsp->tx_volume) {
if (dsp_debug & DEBUG_DSP_DTMF)
printk(KERN_DEBUG "%s dsp %s cannot do hardware DTMF, "
"because tx_volume is changed\n",
__func__, dsp->name);
hardware = 0;
}
if (dsp->rx_volume) {
if (dsp_debug & DEBUG_DSP_DTMF)
printk(KERN_DEBUG "%s dsp %s cannot do hardware DTMF, "
"because rx_volume is changed\n",
__func__, dsp->name);
hardware = 0;
}
/* check if encryption is enabled */
if (dsp->bf_enable) {
if (dsp_debug & DEBUG_DSP_DTMF)
printk(KERN_DEBUG "%s dsp %s cannot do hardware DTMF, "
"because encryption is enabled\n",
__func__, dsp->name);
hardware = 0;
}
/* check if pipeline exists */
if (dsp->pipeline.inuse) {
if (dsp_debug & DEBUG_DSP_DTMF)
printk(KERN_DEBUG "%s dsp %s cannot do hardware DTMF, "
"because pipeline exists.\n",
__func__, dsp->name);
hardware = 0;
}
dsp->dtmf.hardware = hardware;
dsp->dtmf.software = !hardware;
}
/*************************************************************
* calculate the coefficients of the given sample and decode *
*************************************************************/
/* the given sample is decoded. if the sample is not long enough for a
* complete frame, the decoding is finished and continued with the next
* call of this function.
*
* the algorithm is very good for detection with a minimum of errors. i
* tested it allot. it even works with very short tones (40ms). the only
* disadvantage is, that it doesn't work good with different volumes of both
* tones. this will happen, if accoustically coupled dialers are used.
* it sometimes detects tones during speech, which is normal for decoders.
* use sequences to given commands during calls.
*
* dtmf - points to a structure of the current dtmf state
* spl and len - the sample
* fmt - 0 = alaw, 1 = ulaw, 2 = coefficients from HFC DTMF hw-decoder
*/
u8
*dsp_dtmf_goertzel_decode(struct dsp *dsp, u8 *data, int len, int fmt)
{
u8 what;
int size;
signed short *buf;
s32 sk, sk1, sk2;
int k, n, i;
s32 *hfccoeff;
s32 result[NCOEFF], tresh, treshl;
int lowgroup, highgroup;
s64 cos2pik_;
dsp->dtmf.digits[0] = '\0';
/* Note: The function will loop until the buffer has not enough samples
* left to decode a full frame.
*/
again:
/* convert samples */
size = dsp->dtmf.size;
buf = dsp->dtmf.buffer;
switch (fmt) {
case 0: /* alaw */
case 1: /* ulaw */
while (size < DSP_DTMF_NPOINTS && len) {
buf[size++] = dsp_audio_law_to_s32[*data++];
len--;
}
break;
case 2: /* HFC coefficients */
default:
if (len < 64) {
if (len > 0)
printk(KERN_ERR "%s: coefficients have invalid "
"size. (is=%d < must=%d)\n",
__func__, len, 64);
return dsp->dtmf.digits;
}
hfccoeff = (s32 *)data;
for (k = 0; k < NCOEFF; k++) {
sk2 = (*hfccoeff++) >> 4;
sk = (*hfccoeff++) >> 4;
if (sk > 32767 || sk < -32767 || sk2 > 32767
|| sk2 < -32767)
printk(KERN_WARNING
"DTMF-Detection overflow\n");
/* compute |X(k)|**2 */
result[k] =
(sk * sk) -
(((cos2pik[k] * sk) >> 15) * sk2) +
(sk2 * sk2);
}
data += 64;
len -= 64;
goto coefficients;
break;
}
dsp->dtmf.size = size;
if (size < DSP_DTMF_NPOINTS)
return dsp->dtmf.digits;
dsp->dtmf.size = 0;
/* now we have a full buffer of signed long samples - we do goertzel */
for (k = 0; k < NCOEFF; k++) {
sk = 0;
sk1 = 0;
sk2 = 0;
buf = dsp->dtmf.buffer;
cos2pik_ = cos2pik[k];
for (n = 0; n < DSP_DTMF_NPOINTS; n++) {
sk = ((cos2pik_ * sk1) >> 15) - sk2 + (*buf++);
sk2 = sk1;
sk1 = sk;
}
sk >>= 8;
sk2 >>= 8;
if (sk > 32767 || sk < -32767 || sk2 > 32767 || sk2 < -32767)
printk(KERN_WARNING "DTMF-Detection overflow\n");
/* compute |X(k)|**2 */
result[k] =
(sk * sk) -
(((cos2pik[k] * sk) >> 15) * sk2) +
(sk2 * sk2);
}
/* our (squared) coefficients have been calculated, we need to process
* them.
*/
coefficients:
tresh = 0;
for (i = 0; i < NCOEFF; i++) {
if (result[i] < 0)
result[i] = 0;
if (result[i] > dsp->dtmf.treshold) {
if (result[i] > tresh)
tresh = result[i];
}
}
if (tresh == 0) {
what = 0;
goto storedigit;
}
if (dsp_debug & DEBUG_DSP_DTMFCOEFF)
printk(KERN_DEBUG "a %3d %3d %3d %3d %3d %3d %3d %3d"
" tr:%3d r %3d %3d %3d %3d %3d %3d %3d %3d\n",
result[0] / 10000, result[1] / 10000, result[2] / 10000,
result[3] / 10000, result[4] / 10000, result[5] / 10000,
result[6] / 10000, result[7] / 10000, tresh / 10000,
result[0] / (tresh / 100), result[1] / (tresh / 100),
result[2] / (tresh / 100), result[3] / (tresh / 100),
result[4] / (tresh / 100), result[5] / (tresh / 100),
result[6] / (tresh / 100), result[7] / (tresh / 100));
/* calc digit (lowgroup/highgroup) */
lowgroup = -1;
highgroup = -1;
treshl = tresh >> 3; /* tones which are not on, must be below 9 dB */
tresh = tresh >> 2; /* touchtones must match within 6 dB */
for (i = 0; i < NCOEFF; i++) {
if (result[i] < treshl)
continue; /* ignore */
if (result[i] < tresh) {
lowgroup = -1;
highgroup = -1;
break; /* noise in between */
}
/* good level found. This is allowed only one time per group */
if (i < NCOEFF / 2) {
/* lowgroup */
if (lowgroup >= 0) {
/* Bad. Another tone found. */
lowgroup = -1;
break;
} else
lowgroup = i;
} else {
/* higroup */
if (highgroup >= 0) {
/* Bad. Another tone found. */
highgroup = -1;
break;
} else
highgroup = i - (NCOEFF / 2);
}
}
/* get digit or null */
what = 0;
if (lowgroup >= 0 && highgroup >= 0)
what = dtmf_matrix[lowgroup][highgroup];
storedigit:
if (what && (dsp_debug & DEBUG_DSP_DTMF))
printk(KERN_DEBUG "DTMF what: %c\n", what);
if (dsp->dtmf.lastwhat != what)
dsp->dtmf.count = 0;
/* the tone (or no tone) must remain 3 times without change */
if (dsp->dtmf.count == 2) {
if (dsp->dtmf.lastdigit != what) {
dsp->dtmf.lastdigit = what;
if (what) {
if (dsp_debug & DEBUG_DSP_DTMF)
printk(KERN_DEBUG "DTMF digit: %c\n",
what);
if ((strlen(dsp->dtmf.digits) + 1)
< sizeof(dsp->dtmf.digits)) {
dsp->dtmf.digits[strlen(
dsp->dtmf.digits) + 1] = '\0';
dsp->dtmf.digits[strlen(
dsp->dtmf.digits)] = what;
}
}
}
} else
dsp->dtmf.count++;
dsp->dtmf.lastwhat = what;
goto again;
}
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