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00001 /* 00002 * SpanDSP - a series of DSP components for telephony 00003 * 00004 * dtmf.h - DTMF tone generation and detection. 00005 * 00006 * Written by Steve Underwood <steveu@coppice.org> 00007 * 00008 * Copyright (C) 2001, 2005 Steve Underwood 00009 * 00010 * All rights reserved. 00011 * 00012 * This program is free software; you can redistribute it and/or modify 00013 * it under the terms of the GNU Lesser General Public License version 2.1, 00014 * as published by the Free Software Foundation. 00015 * 00016 * This program is distributed in the hope that it will be useful, 00017 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00018 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00019 * GNU Lesser General Public License for more details. 00020 * 00021 * You should have received a copy of the GNU Lesser General Public 00022 * License along with this program; if not, write to the Free Software 00023 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 00024 */ 00025 00026 #if !defined(_SPANDSP_DTMF_H_) 00027 #define _SPANDSP_DTMF_H_ 00028 00029 /*! \page dtmf_rx_page DTMF receiver 00030 \section dtmf_rx_page_sec_1 What does it do? 00031 The DTMF receiver detects the standard DTMF digits. It is compliant with 00032 ITU-T Q.23, ITU-T Q.24, and the local DTMF specifications of most administrations. 00033 Its passes the test suites. It also scores *very* well on the standard 00034 talk-off tests. 00035 00036 The current design uses floating point extensively. It is not tolerant of DC. 00037 It is expected that a DC restore stage will be placed before the DTMF detector. 00038 Unless the dial tone filter is switched on, the detector has poor tolerance 00039 of dial tone. Whether this matter depends on your application. If you are using 00040 the detector in an IVR application you will need proper echo cancellation to 00041 get good performance in the presence of speech prompts, so dial tone will not 00042 exist. If you do need good dial tone tolerance, a dial tone filter can be 00043 enabled in the detector. 00044 00045 The DTMF receiver's design assumes the channel is free of any DC component. 00046 00047 \section dtmf_rx_page_sec_2 How does it work? 00048 Like most other DSP based DTMF detector's, this one uses the Goertzel algorithm 00049 to look for the DTMF tones. What makes each detector design different is just how 00050 that algorithm is used. 00051 00052 Basic DTMF specs: 00053 - Minimum tone on = 40ms 00054 - Minimum tone off = 50ms 00055 - Maximum digit rate = 10 per second 00056 - Normal twist <= 8dB accepted 00057 - Reverse twist <= 4dB accepted 00058 - S/N >= 15dB will detect OK 00059 - Attenuation <= 26dB will detect OK 00060 - Frequency tolerance +- 1.5% will detect, +-3.5% will reject 00061 00062 TODO: 00063 */ 00064 00065 /*! \page dtmf_tx_page DTMF tone generation 00066 \section dtmf_tx_page_sec_1 What does it do? 00067 00068 The DTMF tone generation module provides for the generation of the 00069 repertoire of 16 DTMF dual tones. 00070 00071 \section dtmf_tx_page_sec_2 How does it work? 00072 */ 00073 00074 #define MAX_DTMF_DIGITS 128 00075 00076 typedef void (*digits_rx_callback_t)(void *user_data, const char *digits, int len); 00077 00078 /*! 00079 DTMF generator state descriptor. This defines the state of a single 00080 working instance of a DTMF generator. 00081 */ 00082 typedef struct dtmf_tx_state_s dtmf_tx_state_t; 00083 00084 /*! 00085 DTMF digit detector descriptor. 00086 */ 00087 typedef struct dtmf_rx_state_s dtmf_rx_state_t; 00088 00089 #if defined(__cplusplus) 00090 extern "C" 00091 { 00092 #endif 00093 00094 /*! \brief Generate a buffer of DTMF tones. 00095 \param s The DTMF generator context. 00096 \param amp The buffer for the generated signal. 00097 \param max_samples The required number of generated samples. 00098 \return The number of samples actually generated. This may be less than 00099 max_samples if the input buffer empties. */ 00100 SPAN_DECLARE(int) dtmf_tx(dtmf_tx_state_t *s, int16_t amp[], int max_samples); 00101 00102 /*! \brief Put a string of digits in a DTMF generator's input buffer. 00103 \param s The DTMF generator context. 00104 \param digits The string of digits to be added. 00105 \param len The length of the string of digits. If negative, the string is 00106 assumed to be a NULL terminated string. 00107 \return The number of digits actually added. This may be less than the 00108 length of the digit string, if the buffer fills up. */ 00109 SPAN_DECLARE(int) dtmf_tx_put(dtmf_tx_state_t *s, const char *digits, int len); 00110 00111 /*! \brief Change the transmit level for a DTMF tone generator context. 00112 \param s The DTMF generator context. 00113 \param level The level of the low tone, in dBm0. 00114 \param twist The twist, in dB. */ 00115 SPAN_DECLARE(void) dtmf_tx_set_level(dtmf_tx_state_t *s, int level, int twist); 00116 00117 /*! \brief Change the transmit on and off time for a DTMF tone generator context. 00118 \param s The DTMF generator context. 00119 \param on-time The on time, in ms. 00120 \param off_time The off time, in ms. */ 00121 SPAN_DECLARE(void) dtmf_tx_set_timing(dtmf_tx_state_t *s, int on_time, int off_time); 00122 00123 /*! \brief Initialise a DTMF tone generator context. 00124 \param s The DTMF generator context. 00125 \return A pointer to the DTMF generator context. */ 00126 SPAN_DECLARE(dtmf_tx_state_t *) dtmf_tx_init(dtmf_tx_state_t *s); 00127 00128 /*! \brief Release a DTMF tone generator context. 00129 \param s The DTMF tone generator context. 00130 \return 0 for OK, else -1. */ 00131 SPAN_DECLARE(int) dtmf_tx_release(dtmf_tx_state_t *s); 00132 00133 /*! \brief Free a DTMF tone generator context. 00134 \param s The DTMF tone generator context. 00135 \return 0 for OK, else -1. */ 00136 SPAN_DECLARE(int) dtmf_tx_free(dtmf_tx_state_t *s); 00137 00138 /*! Set a optional realtime callback for a DTMF receiver context. This function 00139 is called immediately a confirmed state change occurs in the received DTMF. It 00140 is called with the ASCII value for a DTMF tone pair, or zero to indicate no tone 00141 is being received. 00142 \brief Set a realtime callback for a DTMF receiver context. 00143 \param s The DTMF receiver context. 00144 \param callback Callback routine used to report the start and end of digits. 00145 \param user_data An opaque pointer which is associated with the context, 00146 and supplied in callbacks. */ 00147 SPAN_DECLARE(void) dtmf_rx_set_realtime_callback(dtmf_rx_state_t *s, 00148 tone_report_func_t callback, 00149 void *user_data); 00150 00151 /*! \brief Adjust a DTMF receiver context. 00152 \param s The DTMF receiver context. 00153 \param filter_dialtone TRUE to enable filtering of dialtone, FALSE 00154 to disable, < 0 to leave unchanged. 00155 \param twist Acceptable twist, in dB. < 0 to leave unchanged. 00156 \param reverse_twist Acceptable reverse twist, in dB. < 0 to leave unchanged. 00157 \param threshold The minimum acceptable tone level for detection, in dBm0. 00158 <= -99 to leave unchanged. */ 00159 SPAN_DECLARE(void) dtmf_rx_parms(dtmf_rx_state_t *s, 00160 int filter_dialtone, 00161 int twist, 00162 int reverse_twist, 00163 int threshold); 00164 00165 /*! Process a block of received DTMF audio samples. 00166 \brief Process a block of received DTMF audio samples. 00167 \param s The DTMF receiver context. 00168 \param amp The audio sample buffer. 00169 \param samples The number of samples in the buffer. 00170 \return The number of samples unprocessed. */ 00171 SPAN_DECLARE(int) dtmf_rx(dtmf_rx_state_t *s, const int16_t amp[], int samples); 00172 00173 /*! Get the status of DTMF detection during processing of the last audio 00174 chunk. 00175 \brief Get the status of DTMF detection during processing of the last 00176 audio chunk. 00177 \param s The DTMF receiver context. 00178 \return The current digit status. Either 'x' for a "maybe" condition, or the 00179 digit being detected. */ 00180 SPAN_DECLARE(int) dtmf_rx_status(dtmf_rx_state_t *s); 00181 00182 /*! \brief Get a string of digits from a DTMF receiver's output buffer. 00183 \param s The DTMF receiver context. 00184 \param digits The buffer for the received digits. 00185 \param max The maximum number of digits to be returned, 00186 \return The number of digits actually returned. */ 00187 SPAN_DECLARE(size_t) dtmf_rx_get(dtmf_rx_state_t *s, char *digits, int max); 00188 00189 /*! \brief Initialise a DTMF receiver context. 00190 \param s The DTMF receiver context. 00191 \param callback An optional callback routine, used to report received digits. If 00192 no callback routine is set, digits may be collected, using the dtmf_rx_get() 00193 function. 00194 \param user_data An opaque pointer which is associated with the context, 00195 and supplied in callbacks. 00196 \return A pointer to the DTMF receiver context. */ 00197 SPAN_DECLARE(dtmf_rx_state_t *) dtmf_rx_init(dtmf_rx_state_t *s, 00198 digits_rx_callback_t callback, 00199 void *user_data); 00200 00201 /*! \brief Release a DTMF receiver context. 00202 \param s The DTMF receiver context. 00203 \return 0 for OK, else -1. */ 00204 SPAN_DECLARE(int) dtmf_rx_release(dtmf_rx_state_t *s); 00205 00206 /*! \brief Free a DTMF receiver context. 00207 \param s The DTMF receiver context. 00208 \return 0 for OK, else -1. */ 00209 SPAN_DECLARE(int) dtmf_rx_free(dtmf_rx_state_t *s); 00210 00211 #if defined(__cplusplus) 00212 } 00213 #endif 00214 00215 #endif 00216 /*- End of file ------------------------------------------------------------*/