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linux/drivers/isdn/mISDN/dsp_dtmf.c
Karsten Keil 960366cf8d Add mISDN DSP 
Enable support for digital audio processing capability.
This module may be used for special applications that require
cross connecting of bchannels, conferencing, dtmf decoding
echo cancelation, tone generation, and Blowfish encryption and
decryption.
It may use hardware features if available.

Signed-off-by: Karsten Keil <kkeil@suse.de>
2008-07-27 01:56:38 +02:00

304 lines
7.4 KiB
C
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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->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 speach, 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 inbetween */
}
/* 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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