1 /* 2 * SpanDSP - a series of DSP components for telephony 3 * 4 * t38_gateway.h - A T.38, less the packet exchange part 5 * 6 * Written by Steve Underwood <steveu@coppice.org> 7 * 8 * Copyright (C) 2005, 2006, 2007 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 /*! \file */ 27 28 #if !defined(_SPANDSP_T38_GATEWAY_H_) 29 #define _SPANDSP_T38_GATEWAY_H_ 30 31 /*! \page t38_gateway_page T.38 real time FAX over IP PSTN gateway 32 \section t38_gateway_page_sec_1 What does it do? 33 34 The T.38 gateway facility provides a robust interface between T.38 IP packet streams and 35 and 8k samples/second audio streams. It provides the buffering and flow control features needed 36 to maximum the tolerance of jitter and packet loss on the IP network. 37 38 \section t38_gateway_page_sec_2 How does it work? 39 */ 40 41 /*! The maximum number of bytes to be zapped, in order to corrupt NSF, 42 NSS and NSC messages, so the receiver does not recognise them. */ 43 #define MAX_NSX_SUPPRESSION 10 44 45 typedef struct t38_gateway_state_s t38_gateway_state_t; 46 47 /*! 48 T.38 gateway real time frame handler. 49 \brief T.38 gateway real time frame handler. 50 \param user_data An opaque pointer. 51 \param incoming True for incoming, false for outgoing. 52 \param msg The HDLC message. 53 \param len The length of the message. 54 */ 55 typedef void (*t38_gateway_real_time_frame_handler_t)(void *user_data, 56 bool incoming, 57 const uint8_t *msg, 58 int len); 59 60 /*! 61 T.38 gateway results. 62 */ 63 typedef struct 64 { 65 /*! \brief The current bit rate for image transfer. */ 66 int bit_rate; 67 /*! \brief True if error correcting mode is used. */ 68 bool error_correcting_mode; 69 /*! \brief The number of pages transferred so far. */ 70 int pages_transferred; 71 } t38_stats_t; 72 73 #if defined(__cplusplus) 74 extern "C" 75 { 76 #endif 77 78 /*! \brief Initialise a gateway mode T.38 context. 79 \param s The T.38 context. 80 \param tx_packet_handler A callback routine to encapsulate and transmit T.38 packets. 81 \param tx_packet_user_data An opaque pointer passed to the tx_packet_handler routine. 82 \return A pointer to the termination mode T.38 context, or NULL if there was a problem. */ 83 SPAN_DECLARE(t38_gateway_state_t *) t38_gateway_init(t38_gateway_state_t *s, 84 t38_tx_packet_handler_t tx_packet_handler, 85 void *tx_packet_user_data); 86 87 /*! Release a gateway mode T.38 context. 88 \brief Release a T.38 context. 89 \param s The T.38 context. 90 \return 0 for OK, else -1. */ 91 SPAN_DECLARE(int) t38_gateway_release(t38_gateway_state_t *s); 92 93 /*! Free a gateway mode T.38 context. 94 \brief Free a T.38 context. 95 \param s The T.38 context. 96 \return 0 for OK, else -1. */ 97 SPAN_DECLARE(int) t38_gateway_free(t38_gateway_state_t *s); 98 99 /*! Process a block of received FAX audio samples. 100 \brief Process a block of received FAX audio samples. 101 \param s The T.38 context. 102 \param amp The audio sample buffer. 103 \param len The number of samples in the buffer. 104 \return The number of samples unprocessed. */ 105 SPAN_DECLARE(int) t38_gateway_rx(t38_gateway_state_t *s, int16_t amp[], int len); 106 107 /*! Apply fake processing when a block of audio samples is missing (e.g due 108 to packet loss). 109 \brief Apply fake received audio processing. 110 \param s The T.38 context. 111 \param len The number of samples to fake. 112 \return The number of samples unprocessed. This should only be non-zero if 113 the software has reached the end of the FAX call. 114 */ 115 SPAN_DECLARE(int) t38_gateway_rx_fillin(t38_gateway_state_t *s, int len); 116 117 /*! Generate a block of FAX audio samples. 118 \brief Generate a block of FAX audio samples. 119 \param s The T.38 context. 120 \param amp The audio sample buffer. 121 \param max_len The number of samples to be generated. 122 \return The number of samples actually generated. 123 */ 124 SPAN_DECLARE(int) t38_gateway_tx(t38_gateway_state_t *s, int16_t amp[], int max_len); 125 126 /*! Control whether error correcting mode (ECM) is allowed. 127 \brief Control whether error correcting mode (ECM) is allowed. 128 \param s The T.38 context. 129 \param ecm_allowed True is ECM is to be allowed. 130 */ 131 SPAN_DECLARE(void) t38_gateway_set_ecm_capability(t38_gateway_state_t *s, bool ecm_allowed); 132 133 /*! Select whether silent audio will be sent when transmit is idle. 134 \brief Select whether silent audio will be sent when transmit is idle. 135 \param s The T.38 context. 136 \param transmit_on_idle True if silent audio should be output when the FAX transmitter is 137 idle. False to transmit zero length audio when the FAX transmitter is idle. The default 138 behaviour is false. 139 */ 140 SPAN_DECLARE(void) t38_gateway_set_transmit_on_idle(t38_gateway_state_t *s, bool transmit_on_idle); 141 142 /*! Specify which modem types are supported by a T.30 context. 143 \brief Specify supported modems. 144 \param s The T.38 context. 145 \param supported_modems Bit field list of the supported modems. 146 */ 147 SPAN_DECLARE(void) t38_gateway_set_supported_modems(t38_gateway_state_t *s, int supported_modems); 148 149 /*! Select whether NSC, NSF, and NSS should be suppressed. It selected, the contents of 150 these messages are forced to zero for all octets beyond the message type. This makes 151 them look like manufacturer specific messages, from a manufacturer which does not exist. 152 \brief Select whether NSC, NSF, and NSS should be suppressed. 153 \param s The T.38 context. 154 \param from_t38 A string of bytes to overwrite the header of any NSC, NSF, and NSS 155 frames passing through the gateway from T.38 the the modem. 156 \param from_t38_len The length of the overwrite string. 157 \param from_modem A string of bytes to overwrite the header of any NSC, NSF, and NSS 158 frames passing through the gateway from the modem to T.38. 159 \param from_modem_len The length of the overwrite string. 160 */ 161 SPAN_DECLARE(void) t38_gateway_set_nsx_suppression(t38_gateway_state_t *s, 162 const uint8_t *from_t38, 163 int from_t38_len, 164 const uint8_t *from_modem, 165 int from_modem_len); 166 167 /*! Select whether talker echo protection tone will be sent for the image modems. 168 \brief Select whether TEP will be sent for the image modems. 169 \param s The T.38 context. 170 \param use_tep True if TEP should be sent. 171 */ 172 SPAN_DECLARE(void) t38_gateway_set_tep_mode(t38_gateway_state_t *s, bool use_tep); 173 174 /*! Select whether non-ECM fill bits are to be removed during transmission. 175 \brief Select whether non-ECM fill bits are to be removed during transmission. 176 \param s The T.38 context. 177 \param remove True if fill bits are to be removed. 178 */ 179 SPAN_DECLARE(void) t38_gateway_set_fill_bit_removal(t38_gateway_state_t *s, bool remove); 180 181 /*! Get the current transfer statistics for the current T.38 session. 182 \brief Get the current transfer statistics. 183 \param s The T.38 context. 184 \param t A pointer to a buffer for the statistics. */ 185 SPAN_DECLARE(void) t38_gateway_get_transfer_statistics(t38_gateway_state_t *s, t38_stats_t *t); 186 187 /*! Get a pointer to the T.38 core IFP packet engine associated with a 188 gateway mode T.38 context. 189 \brief Get a pointer to the T.38 core IFP packet engine associated 190 with a T.38 context. 191 \param s The T.38 context. 192 \return A pointer to the T.38 core context, or NULL. 193 */ 194 SPAN_DECLARE(t38_core_state_t *) t38_gateway_get_t38_core_state(t38_gateway_state_t *s); 195 196 /*! Get a pointer to the logging context associated with a T.38 context. 197 \brief Get a pointer to the logging context associated with a T.38 context. 198 \param s The T.38 context. 199 \return A pointer to the logging context, or NULL. 200 */ 201 SPAN_DECLARE(logging_state_t *) t38_gateway_get_logging_state(t38_gateway_state_t *s); 202 203 /*! Set a callback function for T.30 frame exchange monitoring. This is called from the heart 204 of the signal processing, so don't take too long in the handler routine. 205 \brief Set a callback function for T.30 frame exchange monitoring. 206 \param s The T.30 context. 207 \param handler The callback function. 208 \param user_data An opaque pointer passed to the callback function. */ 209 SPAN_DECLARE(void) t38_gateway_set_real_time_frame_handler(t38_gateway_state_t *s, 210 t38_gateway_real_time_frame_handler_t handler, 211 void *user_data); 212 213 #if defined(__cplusplus) 214 } 215 #endif 216 217 #endif 218 /*- End of file ------------------------------------------------------------*/ 219