00001 /* 00002 * SpanDSP - a series of DSP components for telephony 00003 * 00004 * t38_gateway.h - A T.38, less the packet exchange part 00005 * 00006 * Written by Steve Underwood <steveu@coppice.org> 00007 * 00008 * Copyright (C) 2005, 2006, 2007 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 * $Id: t38_gateway.h,v 1.59 2008/10/13 13:14:01 steveu Exp $ 00026 */ 00027 00028 /*! \file */ 00029 00030 #if !defined(_SPANDSP_T38_GATEWAY_H_) 00031 #define _SPANDSP_T38_GATEWAY_H_ 00032 00033 /*! \page t38_gateway_page T.38 real time FAX over IP PSTN gateway 00034 \section t38_gateway_page_sec_1 What does it do? 00035 00036 The T.38 gateway facility provides a robust interface between T.38 IP packet streams and 00037 and 8k samples/second audio streams. It provides the buffering and flow control features needed 00038 to maximum the tolerance of jitter and packet loss on the IP network. 00039 00040 \section t38_gateway_page_sec_2 How does it work? 00041 */ 00042 00043 #define T38_RX_BUF_LEN 2048 00044 #define T38_TX_HDLC_BUFS 256 00045 /* Make sure the HDLC frame buffers are big enough for ECM frames. */ 00046 #define T38_MAX_HDLC_LEN 260 00047 00048 typedef struct t38_gateway_state_s t38_gateway_state_t; 00049 00050 /*! 00051 T.30 real time frame handler. 00052 \brief T.30 real time frame handler. 00053 \param s The T.30 context. 00054 \param user_data An opaque pointer. 00055 \param direction TRUE for incoming, FALSE for outgoing. 00056 \param msg The HDLC message. 00057 \param len The length of the message. 00058 */ 00059 typedef void (t38_gateway_real_time_frame_handler_t)(t38_gateway_state_t *s, 00060 void *user_data, 00061 int direction, 00062 const uint8_t *msg, 00063 int len); 00064 00065 typedef struct 00066 { 00067 /*! \brief The current bit rate for image transfer. */ 00068 int bit_rate; 00069 /*! \brief TRUE if error correcting mode is used. */ 00070 int error_correcting_mode; 00071 /*! \brief The number of pages transferred so far. */ 00072 int pages_transferred; 00073 } t38_stats_t; 00074 00075 #if defined(__cplusplus) 00076 extern "C" 00077 { 00078 #endif 00079 00080 /*! \brief Initialise a gateway mode T.38 context. 00081 \param s The T.38 context. 00082 \param tx_packet_handler A callback routine to encapsulate and transmit T.38 packets. 00083 \param tx_packet_user_data An opaque pointer passed to the tx_packet_handler routine. 00084 \return A pointer to the termination mode T.38 context, or NULL if there was a problem. */ 00085 t38_gateway_state_t *t38_gateway_init(t38_gateway_state_t *s, 00086 t38_tx_packet_handler_t *tx_packet_handler, 00087 void *tx_packet_user_data); 00088 00089 /*! Free a gateway mode T.38 context. 00090 \brief Free a T.38 context. 00091 \param s The T.38 context. 00092 \return 0 for OK, else -1. */ 00093 int t38_gateway_free(t38_gateway_state_t *s); 00094 00095 /*! Process a block of received FAX audio samples. 00096 \brief Process a block of received FAX audio samples. 00097 \param s The T.38 context. 00098 \param amp The audio sample buffer. 00099 \param len The number of samples in the buffer. 00100 \return The number of samples unprocessed. */ 00101 int t38_gateway_rx(t38_gateway_state_t *s, int16_t amp[], int len); 00102 00103 /*! Generate a block of FAX audio samples. 00104 \brief Generate a block of FAX audio samples. 00105 \param s The T.38 context. 00106 \param amp The audio sample buffer. 00107 \param max_len The number of samples to be generated. 00108 \return The number of samples actually generated. 00109 */ 00110 int t38_gateway_tx(t38_gateway_state_t *s, int16_t amp[], int max_len); 00111 00112 /*! Control whether error correcting mode (ECM) is allowed. 00113 \brief Control whether error correcting mode (ECM) is allowed. 00114 \param s The T.38 context. 00115 \param ecm_allowed TRUE is ECM is to be allowed. 00116 */ 00117 void t38_gateway_set_ecm_capability(t38_gateway_state_t *s, int ecm_allowed); 00118 00119 /*! Select whether silent audio will be sent when transmit is idle. 00120 \brief Select whether silent audio will be sent when transmit is idle. 00121 \param s The T.38 context. 00122 \param transmit_on_idle TRUE if silent audio should be output when the FAX transmitter is 00123 idle. FALSE to transmit zero length audio when the FAX transmitter is idle. The default 00124 behaviour is FALSE. 00125 */ 00126 void t38_gateway_set_transmit_on_idle(t38_gateway_state_t *s, int transmit_on_idle); 00127 00128 /*! Specify which modem types are supported by a T.30 context. 00129 \brief Specify supported modems. 00130 \param s The T.38 context. 00131 \param supported_modems Bit field list of the supported modems. 00132 */ 00133 void t38_gateway_set_supported_modems(t38_gateway_state_t *s, int supported_modems); 00134 00135 /*! Select whether NSC, NSF, and NSS should be suppressed. It selected, the contents of 00136 these messages are forced to zero for all octets beyond the message type. This makes 00137 them look like manufacturer specific messages, from a manufacturer which does not exist. 00138 \brief Select whether NSC, NSF, and NSS should be suppressed. 00139 \param s The T.38 context. 00140 \param from_t38 A string of bytes to overwrite the header of any NSC, NSF, and NSS 00141 frames passing through the gateway from T.38 the the modem. 00142 \param from_t38_len The length of the overwrite string. 00143 \param from_modem A string of bytes to overwrite the header of any NSC, NSF, and NSS 00144 frames passing through the gateway from the modem to T.38. 00145 \param from_modem_len The length of the overwrite string. 00146 */ 00147 void t38_gateway_set_nsx_suppression(t38_gateway_state_t *s, 00148 const uint8_t *from_t38, 00149 int from_t38_len, 00150 const uint8_t *from_modem, 00151 int from_modem_len); 00152 00153 /*! Select whether talker echo protection tone will be sent for the image modems. 00154 \brief Select whether TEP will be sent for the image modems. 00155 \param s The T.38 context. 00156 \param use_tep TRUE if TEP should be sent. 00157 */ 00158 void t38_gateway_set_tep_mode(t38_gateway_state_t *s, int use_tep); 00159 00160 /*! Select whether non-ECM fill bits are to be removed during transmission. 00161 \brief Select whether non-ECM fill bits are to be removed during transmission. 00162 \param s The T.38 context. 00163 \param remove TRUE if fill bits are to be removed. 00164 */ 00165 void t38_gateway_set_fill_bit_removal(t38_gateway_state_t *s, int remove); 00166 00167 /*! Get the current transfer statistics for the current T.38 session. 00168 \brief Get the current transfer statistics. 00169 \param s The T.38 context. 00170 \param t A pointer to a buffer for the statistics. */ 00171 void t38_gateway_get_transfer_statistics(t38_gateway_state_t *s, t38_stats_t *t); 00172 00173 /*! Get a pointer to the T.38 core IFP packet engine associated with a 00174 gateway mode T.38 context. 00175 \brief Get a pointer to the T.38 core IFP packet engine associated 00176 with a T.38 context. 00177 \param s The T.38 context. 00178 \return A pointer to the T.38 core context, or NULL. 00179 */ 00180 t38_core_state_t *t38_gateway_get_t38_core_state(t38_gateway_state_t *s); 00181 00182 /*! Get a pointer to the logging context associated with a T.38 context. 00183 \brief Get a pointer to the logging context associated with a T.38 context. 00184 \param s The T.38 context. 00185 \return A pointer to the logging context, or NULL. 00186 */ 00187 logging_state_t *t38_gateway_get_logging_state(t38_gateway_state_t *s); 00188 00189 /*! Set a callback function for T.30 frame exchange monitoring. This is called from the heart 00190 of the signal processing, so don't take too long in the handler routine. 00191 \brief Set a callback function for T.30 frame exchange monitoring. 00192 \param s The T.30 context. 00193 \param handler The callback function. 00194 \param user_data An opaque pointer passed to the callback function. */ 00195 void t38_gateway_set_real_time_frame_handler(t38_gateway_state_t *s, 00196 t38_gateway_real_time_frame_handler_t *handler, 00197 void *user_data); 00198 00199 #if defined(__cplusplus) 00200 } 00201 #endif 00202 00203 #endif 00204 /*- End of file ------------------------------------------------------------*/