drivers/isdn/mISDN/dsp_dtmf.c

   1 /*
   2  * DTMF decoder.
   3  *
   4  * Copyright            by Andreas Eversberg (jolly@eversberg.eu)
   5  *                      based on different decoders such as ISDN4Linux
   6  *
   7  * This software may be used and distributed according to the terms
   8  * of the GNU General Public License, incorporated herein by reference.
   9  *
  10  */
  11
  12 #include <linux/mISDNif.h>
  13 #include <linux/mISDNdsp.h>
  14 #include "core.h"
  15 #include "dsp.h"
  16
  17 #define NCOEFF            8     /* number of frequencies to be analyzed */
  18
  19 /* For DTMF recognition:
  20  * 2 * cos(2 * PI * k / N) precalculated for all k
  21  */
  22 static u64 cos2pik[NCOEFF] =
  23 {
  24         /* k << 15 (source: hfc-4s/8s documentation (www.colognechip.de)) */
  25         55960, 53912, 51402, 48438, 38146, 32650, 26170, 18630
  26 };
  27
  28 /* digit matrix */
  29 static char dtmf_matrix[4][4] =
  30 {
  31         {'1', '2', '3', 'A'},
  32         {'4', '5', '6', 'B'},
  33         {'7', '8', '9', 'C'},
  34         {'*', '0', '#', 'D'}
  35 };
  36
  37 /* dtmf detection using goertzel algorithm
  38  * init function
  39  */
  40 void dsp_dtmf_goertzel_init(struct dsp *dsp)
  41 {
  42         dsp->dtmf.size = 0;
  43         dsp->dtmf.lastwhat = '\0';
  44         dsp->dtmf.lastdigit = '\0';
  45         dsp->dtmf.count = 0;
  46 }
  47
  48 /* check for hardware or software features
  49  */
  50 void dsp_dtmf_hardware(struct dsp *dsp)
  51 {
  52         int hardware = 1;
  53
  54         if (!dsp->dtmf.enable)
  55                 return;
  56
  57         if (!dsp->features.hfc_dtmf)
  58                 hardware = 0;
  59
  60         /* check for volume change */
  61         if (dsp->tx_volume) {
  62                 if (dsp_debug & DEBUG_DSP_DTMF)
  63                         printk(KERN_DEBUG "%s dsp %s cannot do hardware DTMF, "
  64                                 "because tx_volume is changed\n",
  65                                 __func__, dsp->name);
  66                 hardware = 0;
  67         }
  68         if (dsp->rx_volume) {
  69                 if (dsp_debug & DEBUG_DSP_DTMF)
  70                         printk(KERN_DEBUG "%s dsp %s cannot do hardware DTMF, "
  71                                 "because rx_volume is changed\n",
  72                                 __func__, dsp->name);
  73                 hardware = 0;
  74         }
  75         /* check if encryption is enabled */
  76         if (dsp->bf_enable) {
  77                 if (dsp_debug & DEBUG_DSP_DTMF)
  78                         printk(KERN_DEBUG "%s dsp %s cannot do hardware DTMF, "
  79                                 "because encryption is enabled\n",
  80                                 __func__, dsp->name);
  81                 hardware = 0;
  82         }
  83         /* check if pipeline exists */
  84         if (dsp->pipeline.inuse) {
  85                 if (dsp_debug & DEBUG_DSP_DTMF)
  86                         printk(KERN_DEBUG "%s dsp %s cannot do hardware DTMF, "
  87                                 "because pipeline exists.\n",
  88                                 __func__, dsp->name);
  89                 hardware = 0;
  90         }
  91
  92         dsp->dtmf.hardware = hardware;
  93         dsp->dtmf.software = !hardware;
  94 }
  95
  96
  97 /*************************************************************
  98  * calculate the coefficients of the given sample and decode *
  99  *************************************************************/
 100
 101 /* the given sample is decoded. if the sample is not long enough for a
 102  * complete frame, the decoding is finished and continued with the next
 103  * call of this function.
 104  *
 105  * the algorithm is very good for detection with a minimum of errors. i
 106  * tested it allot. it even works with very short tones (40ms). the only
 107  * disadvantage is, that it doesn't work good with different volumes of both
 108  * tones. this will happen, if accoustically coupled dialers are used.
 109  * it sometimes detects tones during speech, which is normal for decoders.
 110  * use sequences to given commands during calls.
 111  *
 112  * dtmf - points to a structure of the current dtmf state
 113  * spl and len - the sample
 114  * fmt - 0 = alaw, 1 = ulaw, 2 = coefficients from HFC DTMF hw-decoder
 115  */
 116
 117 u8
 118 *dsp_dtmf_goertzel_decode(struct dsp *dsp, u8 *data, int len, int fmt)
 119 {
 120         u8 what;
 121         int size;
 122         signed short *buf;
 123         s32 sk, sk1, sk2;
 124         int k, n, i;
 125         s32 *hfccoeff;
 126         s32 result[NCOEFF], tresh, treshl;
 127         int lowgroup, highgroup;
 128         s64 cos2pik_;
 129
 130         dsp->dtmf.digits[0] = '\0';
 131
 132         /* Note: The function will loop until the buffer has not enough samples
 133          * left to decode a full frame.
 134          */
 135 again:
 136         /* convert samples */
 137         size = dsp->dtmf.size;
 138         buf = dsp->dtmf.buffer;
 139         switch (fmt) {
 140         case 0: /* alaw */
 141         case 1: /* ulaw */
 142                 while (size < DSP_DTMF_NPOINTS && len) {
 143                         buf[size++] = dsp_audio_law_to_s32[*data++];
 144                         len--;
 145                 }
 146                 break;
 147
 148         case 2: /* HFC coefficients */
 149         default:
 150                 if (len < 64) {
 151                         if (len > 0)
 152                                 printk(KERN_ERR "%s: coefficients have invalid "
 153                                         "size. (is=%d < must=%d)\n",
 154                                         __func__, len, 64);
 155                         return dsp->dtmf.digits;
 156                 }
 157                 hfccoeff = (s32 *)data;
 158                 for (k = 0; k < NCOEFF; k++) {
 159                         sk2 = (*hfccoeff++)>>4;
 160                         sk = (*hfccoeff++)>>4;
 161                         if (sk > 32767 || sk < -32767 || sk2 > 32767
 162                             || sk2 < -32767)
 163                                 printk(KERN_WARNING
 164                                         "DTMF-Detection overflow\n");
 165                         /* compute |X(k)|**2 */
 166                         result[k] =
 167                                  (sk * sk) -
 168                                  (((cos2pik[k] * sk) >> 15) * sk2) +
 169                                  (sk2 * sk2);
 170                 }
 171                 data += 64;
 172                 len -= 64;
 173                 goto coefficients;
 174                 break;
 175         }
 176         dsp->dtmf.size = size;
 177
 178         if (size < DSP_DTMF_NPOINTS)
 179                 return dsp->dtmf.digits;
 180
 181         dsp->dtmf.size = 0;
 182
 183         /* now we have a full buffer of signed long samples - we do goertzel */
 184         for (k = 0; k < NCOEFF; k++) {
 185                 sk = 0;
 186                 sk1 = 0;
 187                 sk2 = 0;
 188                 buf = dsp->dtmf.buffer;
 189                 cos2pik_ = cos2pik[k];
 190                 for (n = 0; n < DSP_DTMF_NPOINTS; n++) {
 191                         sk = ((cos2pik_*sk1)>>15) - sk2 + (*buf++);
 192                         sk2 = sk1;
 193                         sk1 = sk;
 194                 }
 195                 sk >>= 8;
 196                 sk2 >>= 8;
 197                 if (sk > 32767 || sk < -32767 || sk2 > 32767 || sk2 < -32767)
 198                         printk(KERN_WARNING "DTMF-Detection overflow\n");
 199                 /* compute |X(k)|**2 */
 200                 result[k] =
 201                         (sk * sk) -
 202                         (((cos2pik[k] * sk) >> 15) * sk2) +
 203                         (sk2 * sk2);
 204         }
 205
 206         /* our (squared) coefficients have been calculated, we need to process
 207          * them.
 208          */
 209 coefficients:
 210         tresh = 0;
 211         for (i = 0; i < NCOEFF; i++) {
 212                 if (result[i] < 0)
 213                         result[i] = 0;
 214                 if (result[i] > dsp->dtmf.treshold) {
 215                         if (result[i] > tresh)
 216                                 tresh = result[i];
 217                 }
 218         }
 219
 220         if (tresh == 0) {
 221                 what = 0;
 222                 goto storedigit;
 223         }
 224
 225         if (dsp_debug & DEBUG_DSP_DTMFCOEFF)
 226                 printk(KERN_DEBUG "a %3d %3d %3d %3d %3d %3d %3d %3d"
 227                         " tr:%3d r %3d %3d %3d %3d %3d %3d %3d %3d\n",
 228                         result[0]/10000, result[1]/10000, result[2]/10000,
 229                         result[3]/10000, result[4]/10000, result[5]/10000,
 230                         result[6]/10000, result[7]/10000, tresh/10000,
 231                         result[0]/(tresh/100), result[1]/(tresh/100),
 232                         result[2]/(tresh/100), result[3]/(tresh/100),
 233                         result[4]/(tresh/100), result[5]/(tresh/100),
 234                         result[6]/(tresh/100), result[7]/(tresh/100));
 235
 236         /* calc digit (lowgroup/highgroup) */
 237         lowgroup = -1;
 238         highgroup = -1;
 239         treshl = tresh >> 3;  /* tones which are not on, must be below 9 dB */
 240         tresh = tresh >> 2;  /* touchtones must match within 6 dB */
 241         for (i = 0; i < NCOEFF; i++) {
 242                 if (result[i] < treshl)
 243                         continue;  /* ignore */
 244                 if (result[i] < tresh) {
 245                         lowgroup = -1;
 246                         highgroup = -1;
 247                         break;  /* noise in between */
 248                 }
 249                 /* good level found. This is allowed only one time per group */
 250                 if (i < NCOEFF/2) {
 251                         /* lowgroup */
 252                         if (lowgroup >= 0) {
 253                                 /* Bad. Another tone found. */
 254                                 lowgroup = -1;
 255                                 break;
 256                         } else
 257                                 lowgroup = i;
 258                 } else {
 259                         /* higroup */
 260                         if (highgroup >= 0) {
 261                                 /* Bad. Another tone found. */
 262                                 highgroup = -1;
 263                                 break;
 264                         } else
 265                                 highgroup = i-(NCOEFF/2);
 266                 }
 267         }
 268
 269         /* get digit or null */
 270         what = 0;
 271         if (lowgroup >= 0 && highgroup >= 0)
 272                 what = dtmf_matrix[lowgroup][highgroup];
 273
 274 storedigit:
 275         if (what && (dsp_debug & DEBUG_DSP_DTMF))
 276                 printk(KERN_DEBUG "DTMF what: %c\n", what);
 277
 278         if (dsp->dtmf.lastwhat != what)
 279                 dsp->dtmf.count = 0;
 280
 281         /* the tone (or no tone) must remain 3 times without change */
 282         if (dsp->dtmf.count == 2) {
 283                 if (dsp->dtmf.lastdigit != what) {
 284                         dsp->dtmf.lastdigit = what;
 285                         if (what) {
 286                                 if (dsp_debug & DEBUG_DSP_DTMF)
 287                                         printk(KERN_DEBUG "DTMF digit: %c\n",
 288                                                 what);
 289                                 if ((strlen(dsp->dtmf.digits)+1)
 290                                         < sizeof(dsp->dtmf.digits)) {
 291                                         dsp->dtmf.digits[strlen(
 292                                                 dsp->dtmf.digits)+1] = '\0';
 293                                         dsp->dtmf.digits[strlen(
 294                                                 dsp->dtmf.digits)] = what;
 295                                 }
 296                         }
 297                 }
 298         } else
 299                 dsp->dtmf.count++;
 300
 301         dsp->dtmf.lastwhat = what;
 302
 303         goto again;
 304 }
 305
 306