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