spandsp: dtmf.h Source File

spandsp 0.0.6

dtmf.h
1/*
2 * SpanDSP - a series of DSP components for telephony
3 *
4 * dtmf.h - DTMF tone generation and detection.
5 *
6 * Written by Steve Underwood <steveu@coppice.org>
7 *
8 * Copyright (C) 2001, 2005 Steve Underwood
9 *
10 * All rights reserved.
11 *
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU Lesser General Public License version 2.1,
14 * as published by the Free Software Foundation.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU Lesser General Public License for more details.
20 *
21 * You should have received a copy of the GNU Lesser General Public
22 * License along with this program; if not, write to the Free Software
23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 */
25
26#if !defined(_SPANDSP_DTMF_H_)
27#define _SPANDSP_DTMF_H_
28
29/*! \page dtmf_rx_page DTMF receiver
30\section dtmf_rx_page_sec_1 What does it do?
31The DTMF receiver detects the standard DTMF digits. It is compliant with
32ITU-T Q.23, ITU-T Q.24, and the local DTMF specifications of most administrations.
33Its passes the test suites. It also scores *very* well on the standard
34talk-off tests.
35
36The current design uses floating point extensively. It is not tolerant of DC.
37It is expected that a DC restore stage will be placed before the DTMF detector.
38Unless the dial tone filter is switched on, the detector has poor tolerance
39of dial tone. Whether this matter depends on your application. If you are using
40the detector in an IVR application you will need proper echo cancellation to
41get good performance in the presence of speech prompts, so dial tone will not
42exist. If you do need good dial tone tolerance, a dial tone filter can be
43enabled in the detector.
44
45The DTMF receiver's design assumes the channel is free of any DC component.
46
47\section dtmf_rx_page_sec_2 How does it work?
48Like most other DSP based DTMF detector's, this one uses the Goertzel algorithm
49to look for the DTMF tones. What makes each detector design different is just how
50that algorithm is used.
51
52Basic DTMF specs:
53 - Minimum tone on = 40ms
54 - Minimum tone off = 50ms
55 - Maximum digit rate = 10 per second
56 - Normal twist <= 8dB accepted
57 - Reverse twist <= 4dB accepted
58 - S/N >= 15dB will detect OK
59 - Attenuation <= 26dB will detect OK
60 - Frequency tolerance +- 1.5% will detect, +-3.5% will reject
61
62TODO:
63*/
64
65/*! \page dtmf_tx_page DTMF tone generation
66\section dtmf_tx_page_sec_1 What does it do?
67
68The DTMF tone generation module provides for the generation of the
69repertoire of 16 DTMF dual tones.
70
71\section dtmf_tx_page_sec_2 How does it work?
72*/
73
74#define MAX_DTMF_DIGITS 128
75
76typedef void (*digits_rx_callback_t)(void *user_data, const char *digits, int len);
77
78/*!
79 DTMF generator state descriptor. This defines the state of a single
80 working instance of a DTMF generator.
81*/
82typedef struct dtmf_tx_state_s dtmf_tx_state_t;
83
84/*!
85 DTMF digit detector descriptor.
86*/
87typedef struct dtmf_rx_state_s dtmf_rx_state_t;
88
89#if defined(__cplusplus)
90extern "C"
91{
92#endif
93
94/*! \brief Generate a buffer of DTMF tones.
95 \param s The DTMF generator context.
96 \param amp The buffer for the generated signal.
97 \param max_samples The required number of generated samples.
98 \return The number of samples actually generated. This may be less than
99 max_samples if the input buffer empties. */
100SPAN_DECLARE(int) dtmf_tx(dtmf_tx_state_t *s, int16_t amp[], int max_samples);
101
102/*! \brief Put a string of digits in a DTMF generator's input buffer.
103 \param s The DTMF generator context.
104 \param digits The string of digits to be added.
105 \param len The length of the string of digits. If negative, the string is
106 assumed to be a NULL terminated string.
107 \return The number of digits actually added. This may be less than the
108 length of the digit string, if the buffer fills up. */
109SPAN_DECLARE(int) dtmf_tx_put(dtmf_tx_state_t *s, const char *digits, int len);
110
111/*! \brief Change the transmit level for a DTMF tone generator context.
112 \param s The DTMF generator context.
113 \param level The level of the low tone, in dBm0.
114 \param twist The twist, in dB. */
115SPAN_DECLARE(void) dtmf_tx_set_level(dtmf_tx_state_t *s, int level, int twist);
116
117/*! \brief Change the transmit on and off time for a DTMF tone generator context.
118 \param s The DTMF generator context.
119 \param on-time The on time, in ms.
120 \param off_time The off time, in ms. */
121SPAN_DECLARE(void) dtmf_tx_set_timing(dtmf_tx_state_t *s, int on_time, int off_time);
122
123/*! \brief Initialise a DTMF tone generator context.
124 \param s The DTMF generator context.
125 \return A pointer to the DTMF generator context. */
126SPAN_DECLARE(dtmf_tx_state_t *) dtmf_tx_init(dtmf_tx_state_t *s);
127
128/*! \brief Release a DTMF tone generator context.
129 \param s The DTMF tone generator context.
130 \return 0 for OK, else -1. */
131SPAN_DECLARE(int) dtmf_tx_release(dtmf_tx_state_t *s);
132
133/*! \brief Free a DTMF tone generator context.
134 \param s The DTMF tone generator context.
135 \return 0 for OK, else -1. */
136SPAN_DECLARE(int) dtmf_tx_free(dtmf_tx_state_t *s);
137
138/*! Set a optional realtime callback for a DTMF receiver context. This function
139 is called immediately a confirmed state change occurs in the received DTMF. It
140 is called with the ASCII value for a DTMF tone pair, or zero to indicate no tone
141 is being received.
142 \brief Set a realtime callback for a DTMF receiver context.
143 \param s The DTMF receiver context.
144 \param callback Callback routine used to report the start and end of digits.
145 \param user_data An opaque pointer which is associated with the context,
146 and supplied in callbacks. */
147SPAN_DECLARE(void) dtmf_rx_set_realtime_callback(dtmf_rx_state_t *s,
148 tone_report_func_t callback,
149 void *user_data);
150
151/*! \brief Adjust a DTMF receiver context.
152 \param s The DTMF receiver context.
153 \param filter_dialtone TRUE to enable filtering of dialtone, FALSE
154 to disable, < 0 to leave unchanged.
155 \param twist Acceptable twist, in dB. < 0 to leave unchanged.
156 \param reverse_twist Acceptable reverse twist, in dB. < 0 to leave unchanged.
157 \param threshold The minimum acceptable tone level for detection, in dBm0.
158 <= -99 to leave unchanged. */
159SPAN_DECLARE(void) dtmf_rx_parms(dtmf_rx_state_t *s,
160 int filter_dialtone,
161 int twist,
162 int reverse_twist,
163 int threshold);
164
165/*! Process a block of received DTMF audio samples.
166 \brief Process a block of received DTMF audio samples.
167 \param s The DTMF receiver context.
168 \param amp The audio sample buffer.
169 \param samples The number of samples in the buffer.
170 \return The number of samples unprocessed. */
171SPAN_DECLARE(int) dtmf_rx(dtmf_rx_state_t *s, const int16_t amp[], int samples);
172
173/*! Fake processing of a missing block of received DTMF audio samples.
174 (e.g due to packet loss).
175 \brief Fake processing of a missing block of received DTMF audio samples.
176 \param s The DTMF receiver context.
177 \param len The number of samples to fake.
178 \return The number of samples unprocessed. */
179SPAN_DECLARE(int) dtmf_rx_fillin(dtmf_rx_state_t *s, int samples);
180
181/*! Get the status of DTMF detection during processing of the last audio
182 chunk.
183 \brief Get the status of DTMF detection during processing of the last
184 audio chunk.
185 \param s The DTMF receiver context.
186 \return The current digit status. Either 'x' for a "maybe" condition, or the
187 digit being detected. */
188SPAN_DECLARE(int) dtmf_rx_status(dtmf_rx_state_t *s);
189
190/*! \brief Get a string of digits from a DTMF receiver's output buffer.
191 \param s The DTMF receiver context.
192 \param digits The buffer for the received digits.
193 \param max The maximum number of digits to be returned,
194 \return The number of digits actually returned. */
195SPAN_DECLARE(size_t) dtmf_rx_get(dtmf_rx_state_t *s, char *digits, int max);
196
197/*! \brief Get the logging context associated with a DTMF receiver context.
198 \param s The DTMF receiver context.
199 \return A pointer to the logging context */
200SPAN_DECLARE(logging_state_t *) dtmf_rx_get_logging_state(dtmf_rx_state_t *s);
201
202/*! \brief Initialise a DTMF receiver context.
203 \param s The DTMF receiver context.
204 \param callback An optional callback routine, used to report received digits. If
205 no callback routine is set, digits may be collected, using the dtmf_rx_get()
206 function.
207 \param user_data An opaque pointer which is associated with the context,
208 and supplied in callbacks.
209 \return A pointer to the DTMF receiver context. */
210SPAN_DECLARE(dtmf_rx_state_t *) dtmf_rx_init(dtmf_rx_state_t *s,
211 digits_rx_callback_t callback,
212 void *user_data);
213
214/*! \brief Release a DTMF receiver context.
215 \param s The DTMF receiver context.
216 \return 0 for OK, else -1. */
217SPAN_DECLARE(int) dtmf_rx_release(dtmf_rx_state_t *s);
218
219/*! \brief Free a DTMF receiver context.
220 \param s The DTMF receiver context.
221 \return 0 for OK, else -1. */
222SPAN_DECLARE(int) dtmf_rx_free(dtmf_rx_state_t *s);
223
224#if defined(__cplusplus)
225}
226#endif
227
228#endif
229/*- End of file ------------------------------------------------------------*/
dtmf_tx_set_level
void dtmf_tx_set_level(dtmf_tx_state_t *s, int level, int twist)
Change the transmit level for a DTMF tone generator context.
Definition dtmf.c:551
dtmf_rx_set_realtime_callback
void dtmf_rx_set_realtime_callback(dtmf_rx_state_t *s, tone_report_func_t callback, void *user_data)
Set a realtime callback for a DTMF receiver context.
Definition dtmf.c:363
dtmf_tx_free
int dtmf_tx_free(dtmf_tx_state_t *s)
Free a DTMF tone generator context.
Definition dtmf.c:590
dtmf_rx_get
size_t dtmf_rx_get(dtmf_rx_state_t *s, char *buf, int max)
Get a string of digits from a DTMF receiver's output buffer.
Definition dtmf.c:348
dtmf_rx_get_logging_state
logging_state_t * dtmf_rx_get_logging_state(dtmf_rx_state_t *s)
Get the logging context associated with a DTMF receiver context.
Definition dtmf.c:401
dtmf_tx_init
dtmf_tx_state_t * dtmf_tx_init(dtmf_tx_state_t *s)
Initialise a DTMF tone generator context.
Definition dtmf.c:565
dtmf_tx
int dtmf_tx(dtmf_tx_state_t *s, int16_t amp[], int max_samples)
Generate a buffer of DTMF tones.
Definition dtmf.c:501
dtmf_rx_status
int dtmf_rx_status(dtmf_rx_state_t *s)
Get the status of DTMF detection during processing of the last audio chunk.
Definition dtmf.c:338
dtmf_rx_init
dtmf_rx_state_t * dtmf_rx_init(dtmf_rx_state_t *s, digits_rx_callback_t callback, void *user_data)
Initialise a DTMF receiver context.
Definition dtmf.c:407
dtmf_rx_free
int dtmf_rx_free(dtmf_rx_state_t *s)
Free a DTMF receiver context.
Definition dtmf.c:467
dtmf_rx
int dtmf_rx(dtmf_rx_state_t *s, const int16_t amp[], int samples)
Process a block of received DTMF audio samples.
Definition dtmf.c:102
dtmf_rx_release
int dtmf_rx_release(dtmf_rx_state_t *s)
Release a DTMF receiver context.
Definition dtmf.c:461
dtmf_tx_put
int dtmf_tx_put(dtmf_tx_state_t *s, const char *digits, int len)
Put a string of digits in a DTMF generator's input buffer.
Definition dtmf.c:531
dtmf_tx_release
int dtmf_tx_release(dtmf_tx_state_t *s)
Release a DTMF tone generator context.
Definition dtmf.c:584
dtmf_rx_parms
void dtmf_rx_parms(dtmf_rx_state_t *s, int filter_dialtone, int twist, int reverse_twist, int threshold)
Adjust a DTMF receiver context.
Definition dtmf.c:373
dtmf_rx_fillin
int dtmf_rx_fillin(dtmf_rx_state_t *s, int samples)
Fake processing of a missing block of received DTMF audio samples.
Definition dtmf.c:316
dtmf_tx_set_timing
void dtmf_tx_set_timing(dtmf_tx_state_t *s, int on_time, int off_time)
Change the transmit on and off time for a DTMF tone generator context.
Definition dtmf.c:558
dtmf_rx_state_s
Definition private/dtmf.h:51
dtmf_rx_state_s::reverse_twist
float reverse_twist
Definition private/dtmf.h:83
dtmf_rx_state_s::threshold
float threshold
Definition private/dtmf.h:85
dtmf_rx_state_s::filter_dialtone
int filter_dialtone
Definition private/dtmf.h:61
dtmf_rx_state_s::digits
char digits[MAX_DTMF_DIGITS+1]
Definition private/dtmf.h:108
dtmf_tx_state_s
Definition private/dtmf.h:34
logging_state_s
Definition private/logging.h:34