summaryrefslogtreecommitdiffstats
path: root/drivers/isdn/mISDN/dsp_dtmf.c
blob: efc371c1f0dc02a6f86d4f146fe348051aa111ab (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
/*
 * DTMF decoder.
 *
 * Copyright            by Andreas Eversberg (jolly@eversberg.eu)
 *			based on different decoders such as ISDN4Linux
 *
 * This software may be used and distributed according to the terms
 * of the GNU General Public License, incorporated herein by reference.
 *
 */

#include <linux/mISDNif.h>
#include <linux/mISDNdsp.h>
#include "core.h"
#include "dsp.h"

#define NCOEFF            8     /* number of frequencies to be analyzed */

/* For DTMF recognition:
 * 2 * cos(2 * PI * k / N) precalculated for all k
 */
static u64 cos2pik[NCOEFF] =
{
	/* k << 15 (source: hfc-4s/8s documentation (www.colognechip.de)) */
	55960, 53912, 51402, 48438, 38146, 32650, 26170, 18630
};

/* digit matrix */
static char dtmf_matrix[4][4] =
{
	{'1', '2', '3', 'A'},
	{'4', '5', '6', 'B'},
	{'7', '8', '9', 'C'},
	{'*', '0', '#', 'D'}
};

/* dtmf detection using goertzel algorithm
 * init function
 */
void dsp_dtmf_goertzel_init(struct dsp *dsp)
{
	dsp->dtmf.size = 0;
	dsp->dtmf.lastwhat = '\0';
	dsp->dtmf.lastdigit = '\0';
	dsp->dtmf.count = 0;
}

/* check for hardware or software features
 */
void dsp_dtmf_hardware(struct dsp *dsp)
{
	int hardware = 1;

	if (!dsp->features.hfc_dtmf)
		hardware = 0;

	/* check for volume change */
	if (dsp->tx_volume) {
		if (dsp_debug & DEBUG_DSP_DTMF)
			printk(KERN_DEBUG "%s dsp %s cannot do hardware DTMF, "
				"because tx_volume is changed\n",
				__func__, dsp->name);
		hardware = 0;
	}
	if (dsp->rx_volume) {
		if (dsp_debug & DEBUG_DSP_DTMF)
			printk(KERN_DEBUG "%s dsp %s cannot do hardware DTMF, "
				"because rx_volume is changed\n",
				__func__, dsp->name);
		hardware = 0;
	}
	/* check if encryption is enabled */
	if (dsp->bf_enable) {
		if (dsp_debug & DEBUG_DSP_DTMF)
			printk(KERN_DEBUG "%s dsp %s cannot do hardware DTMF, "
				"because encryption is enabled\n",
				__func__, dsp->name);
		hardware = 0;
	}
	/* check if pipeline exists */
	if (dsp->pipeline.inuse) {
		if (dsp_debug & DEBUG_DSP_DTMF)
			printk(KERN_DEBUG "%s dsp %s cannot do hardware DTMF, "
				"because pipeline exists.\n",
				__func__, dsp->name);
		hardware = 0;
	}

	dsp->dtmf.hardware = hardware;
	dsp->dtmf.software = !hardware;
}


/*************************************************************
 * calculate the coefficients of the given sample and decode *
 *************************************************************/

/* the given sample is decoded. if the sample is not long enough for a
 * complete frame, the decoding is finished and continued with the next
 * call of this function.
 *
 * the algorithm is very good for detection with a minimum of errors. i
 * tested it allot. it even works with very short tones (40ms). the only
 * disadvantage is, that it doesn't work good with different volumes of both
 * tones. this will happen, if accoustically coupled dialers are used.
 * it sometimes detects tones during speach, which is normal for decoders.
 * use sequences to given commands during calls.
 *
 * dtmf - points to a structure of the current dtmf state
 * spl and len - the sample
 * fmt - 0 = alaw, 1 = ulaw, 2 = coefficients from HFC DTMF hw-decoder
 */

u8
*dsp_dtmf_goertzel_decode(struct dsp *dsp, u8 *data, int len, int fmt)
{
	u8 what;
	int size;
	signed short *buf;
	s32 sk, sk1, sk2;
	int k, n, i;
	s32 *hfccoeff;
	s32 result[NCOEFF], tresh, treshl;
	int lowgroup, highgroup;
	s64 cos2pik_;

	dsp->dtmf.digits[0] = '\0';

	/* Note: The function will loop until the buffer has not enough samples
	 * left to decode a full frame.
	 */
again:
	/* convert samples */
	size = dsp->dtmf.size;
	buf = dsp->dtmf.buffer;
	switch (fmt) {
	case 0: /* alaw */
	case 1: /* ulaw */
		while (size < DSP_DTMF_NPOINTS && len) {
			buf[size++] = dsp_audio_law_to_s32[*data++];
			len--;
		}
		break;

	case 2: /* HFC coefficients */
	default:
		if (len < 64) {
			if (len > 0)
				printk(KERN_ERR "%s: coefficients have invalid "
					"size. (is=%d < must=%d)\n",
					__func__, len, 64);
			return dsp->dtmf.digits;
		}
		hfccoeff = (s32 *)data;
		for (k = 0; k < NCOEFF; k++) {
			sk2 = (*hfccoeff++)>>4;
			sk = (*hfccoeff++)>>4;
			if (sk > 32767 || sk < -32767 || sk2 > 32767
			    || sk2 < -32767)
				printk(KERN_WARNING
					"DTMF-Detection overflow\n");
			/* compute |X(k)|**2 */
			result[k] =
				 (sk * sk) -
				 (((cos2pik[k] * sk) >> 15) * sk2) +
				 (sk2 * sk2);
		}
		data += 64;
		len -= 64;
		goto coefficients;
		break;
	}
	dsp->dtmf.size = size;

	if (size < DSP_DTMF_NPOINTS)
		return dsp->dtmf.digits;

	dsp->dtmf.size = 0;

	/* now we have a full buffer of signed long samples - we do goertzel */
	for (k = 0; k < NCOEFF; k++) {
		sk = 0;
		sk1 = 0;
		sk2 = 0;
		buf = dsp->dtmf.buffer;
		cos2pik_ = cos2pik[k];
		for (n = 0; n < DSP_DTMF_NPOINTS; n++) {
			sk = ((cos2pik_*sk1)>>15) - sk2 + (*buf++);
			sk2 = sk1;
			sk1 = sk;
		}
		sk >>= 8;
		sk2 >>= 8;
		if (sk > 32767 || sk < -32767 || sk2 > 32767 || sk2 < -32767)
			printk(KERN_WARNING "DTMF-Detection overflow\n");
		/* compute |X(k)|**2 */
		result[k] =
			(sk * sk) -
			(((cos2pik[k] * sk) >> 15) * sk2) +
			(sk2 * sk2);
	}

	/* our (squared) coefficients have been calculated, we need to process
	 * them.
	 */
coefficients:
	tresh = 0;
	for (i = 0; i < NCOEFF; i++) {
		if (result[i] < 0)
			result[i] = 0;
		if (result[i] > dsp->dtmf.treshold) {
			if (result[i] > tresh)
				tresh = result[i];
		}
	}

	if (tresh == 0) {
		what = 0;
		goto storedigit;
	}

	if (dsp_debug & DEBUG_DSP_DTMFCOEFF)
		printk(KERN_DEBUG "a %3d %3d %3d %3d %3d %3d %3d %3d"
			" tr:%3d r %3d %3d %3d %3d %3d %3d %3d %3d\n",
			result[0]/10000, result[1]/10000, result[2]/10000,
			result[3]/10000, result[4]/10000, result[5]/10000,
			result[6]/10000, result[7]/10000, tresh/10000,
			result[0]/(tresh/100), result[1]/(tresh/100),
			result[2]/(tresh/100), result[3]/(tresh/100),
			result[4]/(tresh/100), result[5]/(tresh/100),
			result[6]/(tresh/100), result[7]/(tresh/100));

	/* calc digit (lowgroup/highgroup) */
	lowgroup = -1;
	highgroup = -1;
	treshl = tresh >> 3;  /* tones which are not on, must be below 9 dB */
	tresh = tresh >> 2;  /* touchtones must match within 6 dB */
	for (i = 0; i < NCOEFF; i++) {
		if (result[i] < treshl)
			continue;  /* ignore */
		if (result[i] < tresh) {
			lowgroup = -1;
			highgroup = -1;
			break;  /* noise inbetween */
		}
		/* good level found. This is allowed only one time per group */
		if (i < NCOEFF/2) {
			/* lowgroup */
			if (lowgroup >= 0) {
				/* Bad. Another tone found. */
				lowgroup = -1;
				break;
			} else
				lowgroup = i;
		} else {
			/* higroup */
			if (highgroup >= 0) {
				/* Bad. Another tone found. */
				highgroup = -1;
				break;
			} else
				highgroup = i-(NCOEFF/2);
		}
	}

	/* get digit or null */
	what = 0;
	if (lowgroup >= 0 && highgroup >= 0)
		what = dtmf_matrix[lowgroup][highgroup];

storedigit:
	if (what && (dsp_debug & DEBUG_DSP_DTMF))
		printk(KERN_DEBUG "DTMF what: %c\n", what);

	if (dsp->dtmf.lastwhat != what)
		dsp->dtmf.count = 0;

	/* the tone (or no tone) must remain 3 times without change */
	if (dsp->dtmf.count == 2) {
		if (dsp->dtmf.lastdigit != what) {
			dsp->dtmf.lastdigit = what;
			if (what) {
				if (dsp_debug & DEBUG_DSP_DTMF)
					printk(KERN_DEBUG "DTMF digit: %c\n",
						what);
				if ((strlen(dsp->dtmf.digits)+1)
					< sizeof(dsp->dtmf.digits)) {
					dsp->dtmf.digits[strlen(
						dsp->dtmf.digits)+1] = '\0';
					dsp->dtmf.digits[strlen(
						dsp->dtmf.digits)] = what;
				}
			}
		}
	} else
		dsp->dtmf.count++;

	dsp->dtmf.lastwhat = what;

	goto again;
}


OpenPOWER on IntegriCloud