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