2 * ----------------------------------------------------------------------------
3 * "THE BEER-WARE LICENSE" (Revision 42):
4 * <phk@FreeBSD.org> wrote this file. As long as you retain this notice you
5 * can do whatever you want with this stuff. If we meet some day, and you think
6 * this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
7 * ----------------------------------------------------------------------------
9 * $Id: dtmfdecode.c,v 1.6 1999/12/13 21:25:24 hm Exp $
11 * $FreeBSD: src/usr.sbin/i4b/dtmfdecode/dtmfdecode.c,v 1.4.2.1 2001/08/01 17:45:02 obrien Exp $
12 * $DragonFly: src/usr.sbin/i4b/dtmfdecode/dtmfdecode.c,v 1.3 2003/11/16 15:17:35 eirikn Exp $
14 * Extract DTMF signalling from ISDN4BSD A-law coded audio data
16 * A-Law to linear conversion from the sox package.
23 /* Integer math scaling factor */
27 #define SIGN_BIT (0x80) /* Sign bit for a A-law byte. */
28 #define QUANT_MASK (0xf) /* Quantization field mask. */
29 #define SEG_SHIFT (4) /* Left shift for segment number. */
30 #define SEG_MASK (0x70) /* Segment field mask. */
33 alaw2linear(unsigned char a_val)
40 t = (a_val & QUANT_MASK) << 4;
41 seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
53 return ((a_val & SIGN_BIT) ? t : -t);
57 /* The frequencies we're trying to detect */
58 static int dtmf[8] = {697, 770, 852, 941, 1209, 1336, 1477, 1633};
60 /* precalculated: p1[kk] = (-cos(2 * 3.141592 * dtmf[kk] / 8000.0) * FSC) */
61 static int p1[8] = {-3497, -3369, -3212, -3027, -2384, -2040, -1635, -1164};
64 /* This is the Q of the filter (pole radius) */
67 #define P2 ((int)(POLRAD*POLRAD*FSC))
70 main(int argc, char **argv)
72 int i, kk, t, nn, s, so, ia;
73 int x, c, d, f, h[8], k[8], n, y[8];
80 for (kk = 0; kk < 8; kk++) {
81 y[kk] = h[kk] = k[kk] = 0;
83 p1[kk] = (-cos(2 * 3.141592 * dtmf[kk] / 8000.0) * FSC);
87 for (i = 0; i < 256; i++) {
89 alaw[i] = alaw2linear(i) / (32768/FSC);
92 /* We encode the tones in 8 bits, translate those to symbol */
95 key[0x11] = '1'; key[0x12] = '4'; key[0x14] = '7'; key[0x18] = '*';
96 key[0x21] = '2'; key[0x22] = '5'; key[0x24] = '8'; key[0x28] = '0';
97 key[0x41] = '3'; key[0x42] = '6'; key[0x44] = '9'; key[0x48] = '#';
98 key[0x81] = 'A'; key[0x82] = 'B'; key[0x84] = 'C'; key[0x88] = 'D';
104 while ((i = getchar()) != EOF)
108 /* Convert to our format */
111 /* Input amplitude */
113 ia += (x - ia) / 128;
115 ia += (-x - ia) / 128;
119 for(kk = 0; kk < 8; kk++) {
122 c = (P2 * (x - k[kk])) / FSC;
124 f = (p1[kk] * (d - h[kk])) / FSC;
129 /* Detect and Average */
131 y[kk] += (n - y[kk]) / 64;
133 y[kk] += (-n - y[kk]) / 64;
136 if (y[kk] > FSC/10 && y[kk] > ia)
140 /* Hysteresis and noise supressor */
142 /* printf("x %d %x -> %x\n",t,so, s); */
145 } else if (nn++ == 520 && key[s]) {
147 /* printf(" %d %x\n",t,s); */