Here's a link to a tutorial. It uses Modem::Vgetty.

VOCP is a Perl on Linux solution that you will want to peek at. It rocks.

The tones are referred to as DTMF, or Dual Tone Multi Frequency. Try Googling phreaker sites for more info.

This code looks great for what I need. I don't want to do any of the phone voice messaging, but it looks relatively easy to cut the parts that I need.

Too bad I am still too new to give a ++, it is definitely deserved here.

And this one looks like the fun sloution to figure out. I think once I figure out what VOCP is doing I'll give a shot at writing my own using vgetty. Understanding it all definitely wouldn't hurt.

Alan

Good point++ Now that you mention it, this is what sidetracked my foray into it.

-Lee

"To be civilized is to deny one's nature."

/*
 * detect.c
 * This program will detect MF tones and normal
 * dtmf tones as well as some other common tones such
 * as BUSY, DIALTONE and RING.
 * The program uses a goertzel algorithm to detect
 * the power of various frequency ranges.
 *
 * input is assumed to be 8 bit samples.  The program
 * can use either signed or unsigned samples according
 * to a compile time option:
 *
 *    cc  -DUNSIGNED detect.c -o detect
 *
 * for unsigned input (soundblaster) and:
 *
 *    cc  detect.c -o detect
 *
 * for signed input (amiga samples)
 * if you dont want flushes,  -DNOFLUSH
 * 
 *                            Tim N.
 */

#include <stdio.h>
#include <math.h>
#include "detect.h"


/*
 * calculate the power of each tone according
 * to a modified goertzel algorithm described in
 *  _digital signal processing applications using the
 *  ADSP-2100 family_ by Analog Devices
 *
 * input is 'data',  N sample values
 *
 * ouput is 'power', NUMTONES values
 *  corresponding to the power of each tone 
 */
calc_power(data,power)
#ifdef UNSIGNED
unsigned char *data;
#else
char *data;
#endif
float *power;
{
  float u0[NUMTONES],u1[NUMTONES],t,in;
  int i,j;
  
  for(j=0; j<NUMTONES; j++) {
    u0[j] = 0.0;
    u1[j] = 0.0;
  }
  for(i=0; i<N; i++) {   /* feedback */
#ifdef UNSIGNED
    in = ((int)data[i] - 128) / 128.0;
#else
    in = data[i] / 128.0;
#endif
    for(j=0; j<NUMTONES; j++) {
      t = u0[j];
      u0[j] = in + coef[j] * u0[j] - u1[j];
      u1[j] = t;
    }
  }
  for(j=0; j<NUMTONES; j++)   /* feedforward */
    power[j] = u0[j] * u0[j] + u1[j] * u1[j] - coef[j] * u0[j] * u1[j]
+; 
  return(0);
}


/*
 * detect which signals are present.
 *
 * return values defined in the include file
 * note: DTMF 3 and MF 7 conflict.  To resolve
 * this the program only reports MF 7 between
 * a KP and an ST, otherwise DTMF 3 is returned
 */
decode(data)
char *data;
{
  float power[NUMTONES],thresh,maxpower;
  int on[NUMTONES],on_count;
  int bcount, rcount, ccount;
  int row, col, b1, b2, i;
  int r[4],c[4],b[8];
  static int MFmode=0;
  
  calc_power(data,power);
  for(i=0, maxpower=0.0; i<NUMTONES;i++)
    if(power[i] > maxpower)
      maxpower = power[i]; 
/*
for(i=0;i<NUMTONES;i++) 
  printf("%f, ",power[i]);
printf("\n");
*/

  if(maxpower < THRESH)  /* silence? */ 
    return(DSIL);
  thresh = RANGE * maxpower;    /* allowable range of powers */
  for(i=0, on_count=0; i<NUMTONES; i++) {
    if(power[i] > thresh) { 
      on[i] = 1;
      on_count ++;
    } else
      on[i] = 0;
  }

/*
printf("%4d: ",on_count);
for(i=0;i<NUMTONES;i++)
  putchar('0' + on[i]);
printf("\n");
*/

  if(on_count == 1) {
    if(on[B7]) 
      return(D24);
    if(on[B8])
      return(D26);
    return(-1);
  }
 
  if(on_count == 2) {
    if(on[X1] && on[X2])
      return(DDT);
    if(on[X2] && on[X3])
      return(DRING);
    if(on[X3] && on[X4])
      return(DBUSY);
    
    b[0]= on[B1]; b[1]= on[B2]; b[2]= on[B3]; b[3]= on[B4];
    b[4]= on[B5]; b[5]= on[B6]; b[6]= on[B7]; b[7]= on[B8];
    c[0]= on[C1]; c[1]= on[C2]; c[2]= on[C3]; c[3]= on[C4];
    r[0]= on[R1]; r[1]= on[R2]; r[2]= on[R3]; r[3]= on[R4];

    for(i=0, bcount=0; i<8; i++) {
      if(b[i]) {
        bcount++;
        b2 = b1;
        b1 = i;
      }
    }
    for(i=0, rcount=0; i<4; i++) {
      if(r[i]) {
        rcount++;
        row = i;
      }
    }
    for(i=0, ccount=0; i<4; i++) {
      if(c[i]) {
        ccount++;
        col = i;
      }
    }

    if(rcount==1 && ccount==1) {   /* DTMF */
      if(col == 3)  /* A,B,C,D */
        return(DA + row);
      else {
        if(row == 3 && col == 0 ) 
           return(DSTAR);
        if(row == 3 && col == 2 )
           return(DPND);
        if(row == 3)
           return(D0);
        if(row == 0 && col == 2) {   /* DTMF 3 conflicts with MF 7 */
          if(!MFmode)
            return(D3);
        } else 
          return(D1 + col + row*3);
      }
    }

    if(bcount == 2) {       /* MF */
      /* b1 has upper number, b2 has lower */
      switch(b1) {
        case 7: return( (b2==6)? D2426: -1); 
        case 6: return(-1);
        case 5: if(b2==2 || b2==3)  /* KP */
                  MFmode=1;
                if(b2==4)  /* ST */
                  MFmode=0; 
                return(DC11 + b2);
        /* MF 7 conflicts with DTMF 3, but if we made it
         * here then DTMF 3 was already tested for 
         */
        case 4: return( (b2==3)? D0: D7 + b2);
        case 3: return(D4 + b2);
        case 2: return(D2 + b2);
        case 1: return(D1);
      }
    }
    return(-1);
  }

  if(on_count == 0)
    return(DSIL);
  return(-1); 
}

read_frame(fd,buf)
int fd;
char *buf;
{
  int i,x;

  for(i=0; i<N; ) {
    x = read(fd, &buf[i], N-i);
    if(x <= 0) 
      return(0);
    i += x;
  } 
  return(1);
}

/*
 * read in frames, output the decoded
 * results
 */
dtmf_to_ascii(fd1, fd2)
int fd1;
FILE *fd2;
{
  int x,last= DSIL;
  char frame[N+5];
  int silence_time;

  while(read_frame(fd1, frame)) {
    x = decode(frame); 
/*
if(x== -1) putchar('-');
if(x==DSIL) putchar(' ');
if(x!=DSIL && x!=-1) putchar('a' + x);
fflush(stdout);
continue;
*/

    if(x >= 0) {
      if(x == DSIL)
        silence_time += (silence_time>=0)?1:0 ;
      else
        silence_time= 0;
      if(silence_time == FLUSH_TIME) {
        fputs("\n",fd2);
        silence_time= -1;   /* stop counting */
      }

      if(x != DSIL && x != last &&
         (last == DSIL || last==D24 || last == D26 ||
          last == D2426 || last == DDT || last == DBUSY ||
          last == DRING) )  { 
        fputs(dtran[x], fd2);
#ifndef NOFLUSH
        fflush(fd2);
#endif
      }
      last = x;
    }
  }
  fputs("\n",fd2);
}

main(argc,argv) 
int argc;
char **argv;
{
  FILE *output;
  int input;

  input = 0;
  output = stdout;
  switch(argc) {
    case 1:  break;
    case 3:  output = fopen(argv[2],"w");
             if(!output) {
               perror(argv[2]);
               return(-1);
             }
             /* fall through */
    case 2:  input = open(argv[1],0);
             if(input < 0) {
               perror(argv[1]);
               return(-1);
             }
             break;
     default:
        fprintf(stderr,"usage:  %s [input [output]]\n",argv[0]);
        return(-1);
  }
  dtmf_to_ascii(input,output);
  fputs("Done.\n",output);
  return(0);
}
[download]

and here is detect.h

/* 
 *
 * goertzel aglorithm, find the power of different
 * frequencies in an N point DFT.
 *
 * ftone/fsample = k/N   
 * k and N are integers.  fsample is 8000 (8khz)
 * this means the *maximum* frequency resolution
 * is fsample/N (each step in k corresponds to a
 * step of fsample/N hz in ftone)
 *
 * N was chosen to minimize the sum of the K errors for
 * all the tones detected...  here are the results :
 *
 * Best N is 240, with the sum of all errors = 3.030002
 * freq  freq actual   k     kactual  kerr
 * ---- ------------  ------ ------- -----
 *  350 (366.66667)   10.500 (11)    0.500
 *  440 (433.33333)   13.200 (13)    0.200
 *  480 (466.66667)   14.400 (14)    0.400
 *  620 (633.33333)   18.600 (19)    0.400
 *  697 (700.00000)   20.910 (21)    0.090
 *  700 (700.00000)   21.000 (21)    0.000
 *  770 (766.66667)   23.100 (23)    0.100
 *  852 (866.66667)   25.560 (26)    0.440
 *  900 (900.00000)   27.000 (27)    0.000
 *  941 (933.33333)   28.230 (28)    0.230
 * 1100 (1100.00000)  33.000 (33)    0.000
 * 1209 (1200.00000)  36.270 (36)    0.270
 * 1300 (1300.00000)  39.000 (39)    0.000
 * 1336 (1333.33333)  40.080 (40)    0.080
 **** I took out 1477.. too close to 1500
 * 1477 (1466.66667)  44.310 (44)    0.310
 ****
 * 1500 (1500.00000)  45.000 (45)    0.000
 * 1633 (1633.33333)  48.990 (49)    0.010
 * 1700 (1700.00000)  51.000 (51)    0.000
 * 2400 (2400.00000)  72.000 (72)    0.000
 * 2600 (2600.00000)  78.000 (78)    0.000
 *
 * notice, 697 and 700hz are indestinguishable (same K)
 * all other tones have a seperate k value.  
 * these two tones must be treated as identical for our
 * analysis.
 *
 * The worst tones to detect are 350 (error = 0.5, 
 * detet 367 hz) and 852 (error = 0.44, detect 867hz). 
 * all others are very close.
 *
 */

#define FSAMPLE  8000
#define N        240

int k[] = { 11, 13, 14, 19, 21, 23, 26, 27, 28, 33, 36, 39, 40,
 /*44,*/ 45, 49, 51, 72, 78, };

/* coefficients for above k's as:
 *   2 * cos( 2*pi* k/N )
 */
float coef[] = {
1.917639, 1.885283, 1.867161, 1.757634, 
1.705280, 1.648252, 1.554292, 1.520812, 1.486290, 
1.298896, 1.175571, 1.044997, 1.000000, /* 0.813473,*/ 
0.765367, 0.568031, 0.466891, -0.618034, -0.907981,  };

#define X1    0    /* 350 dialtone */
#define X2    1    /* 440 ring, dialtone */
#define X3    2    /* 480 ring, busy */
#define X4    3    /* 620 busy */

#define R1    4    /* 697, dtmf row 1 */
#define R2    5    /* 770, dtmf row 2 */
#define R3    6    /* 852, dtmf row 3 */
#define R4    8    /* 941, dtmf row 4 */
#define C1   10    /* 1209, dtmf col 1 */
#define C2   12    /* 1336, dtmf col 2 */
#define C3   13    /* 1477, dtmf col 3 */
#define C4   14    /* 1633, dtmf col 4 */

#define B1    4    /* 700, blue box 1 */
#define B2    7    /* 900, bb 2 */
#define B3    9    /* 1100, bb 3 */
#define B4   11    /* 1300, bb4 */
#define B5   13    /* 1500, bb5 */
#define B6   15    /* 1700, bb6 */
#define B7   16    /* 2400, bb7 */
#define B8   17    /* 2600, bb8 */


#define NUMTONES 18 

/* values returned by detect 
 *  0-9     DTMF 0 through 9 or MF 0-9
 *  10-11   DTMF *, #
 *  12-15   DTMF A,B,C,D
 *  16-20   MF last column: C11, C12, KP1, KP2, ST
 *  21      2400
 *  22      2600
 *  23      2400 + 2600
 *  24      DIALTONE
 *  25      RING
 *  26      BUSY
 *  27      silence
 *  -1      invalid
 */
#define D0    0
#define D1    1
#define D2    2
#define D3    3
#define D4    4
#define D5    5
#define D6    6
#define D7    7
#define D8    8
#define D9    9
#define DSTAR 10
#define DPND  11
#define DA    12
#define DB    13
#define DC    14
#define DD    15
#define DC11  16
#define DC12  17
#define DKP1  18
#define DKP2  19
#define DST   20
#define D24   21 
#define D26   22
#define D2426 23
#define DDT   24
#define DRING 25
#define DBUSY 26
#define DSIL  27

/* translation of above codes into text */
char *dtran[] = {
  "0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
  "*", "#", "A", "B", "C", "D", 
  "+C11 ", "+C12 ", " KP1+", " KP2+", "+ST ",
  " 2400 ", " 2600 ", " 2400+2600 ",
  " DIALTONE ", " RING ", " BUSY ","" };

#define RANGE  0.1           /* any thing higher than RANGE*peak is "o
+n" */
#define THRESH 100.0         /* minimum level for the loudest tone */
#define FLUSH_TIME 100       /* 100 frames = 3 seconds */
[download]

May be this is OT...

I would also recommend cards from www.voicetronix.com.au that work well with Bayonne or with a Perl library. Voicetronix products are open source friendly.

Ciao, Valerio

While I don't know of any perl-centric solutions to the problem of DTMF recognition beyond using PDL to implement a Fast Fourier Transform of some sort, to determine frequency and mapping that to a list of frequencies/dtmf tones...
There is a library called 'amTapi', that's fully TAPI compliant. amTapi purports to support DTMF detection and playback of wave files to telephony devices (among other features). It's written in C++, but you could (most likely) easily interface to it using XS. If you do happen make an XS interface, please share! =)

At any rate, since you're on windows, you should *definately* read up on TAPI which is the standard API for telephony devices under Win32.

hmmmm, amTapi can decipher the CallerID stream. *That* would allow the script to run or not run based on the incoming phone number.

Arg! So many things that I want to add in now. Trying to plan and implement solutions one at a time is going to be frustrating. I can see there always being something on the horizon waiting to be added.

As for making an XS interface, I don't know that I would hold my breath. I am nowhere near that level yet. Getting my script to determine that a number '5' has been pushed on the other end is quite enough challenge right now.

............

You know, after reviewing some of the TAPI documentation, getting perl to see my modem on a win machine will be challenge enough!

Thanks to you and ony other posters I have not already thanked. This is more information than I ever thought I would get.

Ahh, but it is the challenges that drive us to learn. I felt that way myself, a while back, seeking to get some MIDI support in Win32. It took a few weeks, and a billion questions, but eventually got a rudimentary interface that I could use built.

Good luck on your quest!

!c