00001 /* 00002 * SpanDSP - a series of DSP components for telephony 00003 * 00004 * dtmf.h - 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 General Public License version 2, as 00014 * 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 General Public License for more details. 00020 * 00021 * You should have received a copy of the GNU General Public License 00022 * along with this program; if not, write to the Free Software 00023 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 00024 * 00025 * $Id: dtmf.h,v 1.16 2007/11/30 12:20:35 steveu Exp $ 00026 */ 00027 00028 #if !defined(_SPANDSP_DTMF_H_) 00029 #define _SPANDSP_DTMF_H_ 00030 00031 /*! \page dtmf_rx_page DTMF receiver 00032 \section dtmf_rx_page_sec_1 What does it do? 00033 The DTMF receiver detects the standard DTMF digits. It is compliant with 00034 ITU-T Q.23, ITU-T Q.24, and the local DTMF specifications of most administrations. 00035 Its passes the test suites. It also scores *very* well on the standard 00036 talk-off tests. 00037 00038 The current design uses floating point extensively. It is not tolerant of DC. 00039 It is expected that a DC restore stage will be placed before the DTMF detector. 00040 Unless the dial tone filter is switched on, the detector has poor tolerance 00041 of dial tone. Whether this matter depends on your application. If you are using 00042 the detector in an IVR application you will need proper echo cancellation to 00043 get good performance in the presence of speech prompts, so dial tone will not 00044 exist. If you do need good dial tone tolerance, a dial tone filter can be 00045 enabled in the detector. 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 (*dtmf_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 00083 { 00084 tone_gen_state_t tones; 00085 int current_sample; 00086 /* The queue structure MUST be followed immediately by the buffer */ 00087 queue_state_t queue; 00088 char digits[MAX_DTMF_DIGITS + 1]; 00089 } dtmf_tx_state_t; 00090 00091 /*! 00092 DTMF digit detector descriptor. 00093 */ 00094 typedef struct 00095 { 00096 /*! Optional callback funcion to deliver received digits. */ 00097 dtmf_rx_callback_t callback; 00098 /*! An opaque pointer passed to the callback function. */ 00099 void *callback_data; 00100 /*! Optional callback funcion to deliver real time digit state changes. */ 00101 tone_report_func_t realtime_callback; 00102 /*! An opaque pointer passed to the real time callback function. */ 00103 void *realtime_callback_data; 00104 /*! TRUE if dialtone should be filtered before processing */ 00105 int filter_dialtone; 00106 /*! Maximum acceptable "normal" (lower bigger than higher) twist ratio */ 00107 float normal_twist; 00108 /*! Maximum acceptable "reverse" (higher bigger than lower) twist ratio */ 00109 float reverse_twist; 00110 00111 /*! 350Hz filter state for the optional dialtone filter */ 00112 float z350_1; 00113 float z350_2; 00114 /*! 440Hz filter state for the optional dialtone filter */ 00115 float z440_1; 00116 float z440_2; 00117 00118 /*! Tone detector working states */ 00119 goertzel_state_t row_out[4]; 00120 goertzel_state_t col_out[4]; 00121 /*! The accumlating total energy on the same period over which the Goertzels work. */ 00122 float energy; 00123 /*! The result of the last tone analysis. */ 00124 uint8_t last_hit; 00125 /*! The confirmed digit we are currently receiving */ 00126 uint8_t in_digit; 00127 /*! The current sample number within a processing block. */ 00128 int current_sample; 00129 00130 /*! The number of digits which have been lost due to buffer overflows. */ 00131 int lost_digits; 00132 /*! The number of digits currently in the digit buffer. */ 00133 int current_digits; 00134 /*! The received digits buffer. This is a NULL terminated string. */ 00135 char digits[MAX_DTMF_DIGITS + 1]; 00136 } dtmf_rx_state_t; 00137 00138 #if defined(__cplusplus) 00139 extern "C" 00140 { 00141 #endif 00142 00143 /*! \brief Generate a buffer of DTMF tones. 00144 \param s The DTMF generator context. 00145 \param amp The buffer for the generated signal. 00146 \param max_samples The required number of generated samples. 00147 \return The number of samples actually generated. This may be less than 00148 max_samples if the input buffer empties. */ 00149 int dtmf_tx(dtmf_tx_state_t *s, int16_t amp[], int max_samples); 00150 00151 /*! \brief Put a string of digits in a DTMF generator's input buffer. 00152 \param s The DTMF generator context. 00153 \param digits The string of digits to be added. 00154 \param len The length of the string of digits. If negative, the string is 00155 assumed to be a NULL terminated string. 00156 \return The number of digits actually added. This may be less than the 00157 length of the digit string, if the buffer fills up. */ 00158 size_t dtmf_tx_put(dtmf_tx_state_t *s, const char *digits, ssize_t len); 00159 00160 /*! \brief Initialise a DTMF tone generator context. 00161 \param s The DTMF generator context. 00162 \return A pointer to the DTMF generator context. */ 00163 dtmf_tx_state_t *dtmf_tx_init(dtmf_tx_state_t *s); 00164 00165 /*! \brief Free a DTMF tone generator context. 00166 \param s The DTMF tone generator context. 00167 \return 0 for OK, else -1. */ 00168 int dtmf_tx_free(dtmf_tx_state_t *s); 00169 00170 /*! Set a optional realtime callback for a DTMF receiver context. This function 00171 is called immediately a confirmed state change occurs in the received DTMF. It 00172 is called with the ASCII value for a DTMF tone pair, or zero to indicate no tone 00173 is being received. 00174 \brief Set a realtime callback for a DTMF receiver context. 00175 \param s The DTMF receiver context. 00176 \param callback Callback routine used to report the start and end of digits. 00177 \param user_data An opaque pointer which is associated with the context, 00178 and supplied in callbacks. */ 00179 void dtmf_rx_set_realtime_callback(dtmf_rx_state_t *s, 00180 tone_report_func_t callback, 00181 void *user_data); 00182 00183 /*! \brief Adjust a DTMF receiver context. 00184 \param s The DTMF receiver context. 00185 \param filter_dialtone TRUE to enable filtering of dialtone, FALSE 00186 to disable, < 0 to leave unchanged. 00187 \param twist Acceptable twist, in dB. < 0 to leave unchanged. 00188 \param reverse_twist Acceptable reverse twist, in dB. < 0 to leave unchanged. */ 00189 void dtmf_rx_parms(dtmf_rx_state_t *s, int filter_dialtone, int twist, int reverse_twist); 00190 00191 /*! Process a block of received DTMF audio samples. 00192 \brief Process a block of received DTMF audio samples. 00193 \param s The DTMF receiver context. 00194 \param amp The audio sample buffer. 00195 \param samples The number of samples in the buffer. 00196 \return The number of samples unprocessed. */ 00197 int dtmf_rx(dtmf_rx_state_t *s, const int16_t amp[], int samples); 00198 00199 /*! Get the status of DTMF detection during processing of the last audio 00200 chunk. 00201 \brief Get the status of DTMF detection during processing of the last 00202 audio chunk. 00203 \param s The DTMF receiver context. 00204 \return The current digit status. Either 'x' for a "maybe" condition, or the 00205 digit being detected. */ 00206 int dtmf_rx_status(dtmf_rx_state_t *s); 00207 00208 /*! \brief Get a string of digits from a DTMF receiver's output buffer. 00209 \param s The DTMF receiver context. 00210 \param digits The buffer for the received digits. 00211 \param max The maximum number of digits to be returned, 00212 \return The number of digits actually returned. */ 00213 size_t dtmf_rx_get(dtmf_rx_state_t *s, char *digits, int max); 00214 00215 /*! \brief Initialise a DTMF receiver context. 00216 \param s The DTMF receiver context. 00217 \param callback An optional callback routine, used to report received digits. If 00218 no callback routine is set, digits may be collected, using the dtmf_rx_get() 00219 function. 00220 \param user_data An opaque pointer which is associated with the context, 00221 and supplied in callbacks. 00222 \return A pointer to the DTMF receiver context. */ 00223 dtmf_rx_state_t *dtmf_rx_init(dtmf_rx_state_t *s, 00224 dtmf_rx_callback_t callback, 00225 void *user_data); 00226 00227 /*! \brief Free a DTMF receiver context. 00228 \param s The DTMF receiver context. 00229 \return 0 for OK, else -1. */ 00230 int dtmf_rx_free(dtmf_rx_state_t *s); 00231 00232 #if defined(__cplusplus) 00233 } 00234 #endif 00235 00236 #endif 00237 /*- End of file ------------------------------------------------------------*/