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1 /*
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2 * SpanDSP - a series of DSP components for telephony
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3 *
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4 * t38_gateway.h - An implementation of T.38, less the packet exchange part
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5 *
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6 * Written by Steve Underwood <steveu@coppice.org>
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7 *
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8 * Copyright (C) 2005 Steve Underwood
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9 *
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10 * All rights reserved.
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11 *
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12 * This program is free software; you can redistribute it and/or modify
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13 * it under the terms of the GNU General Public License version 2, as
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14 * published by the Free Software Foundation.
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15 *
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16 * This program is distributed in the hope that it will be useful,
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17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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19 * GNU General Public License for more details.
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20 *
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21 * You should have received a copy of the GNU General Public License
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22 * along with this program; if not, write to the Free Software
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23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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24 *
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25 * $Id: t38_gateway.h,v 1.17 2006/12/07 13:22:26 steveu Exp $
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26 */
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27
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28 /*! \file */
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29
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30 #if !defined(_T38_GATEWAY_H_)
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31 #define _T38_GATEWAY_H_
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32
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33 /*! \page t38_gateway_page T.38 real time FAX over IP PSTN gateway
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34 \section t38_gateway_page_sec_1 What does it do?
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35
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36 The T.38 gateway facility provides a robust interface between T.38 IP packet streams and
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37 and 8k samples/second audio streams. It provides the buffering and flow control features needed
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38 to maximum the tolerance of jitter and packet loss on the IP network.
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39
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40 \section t38_gateway_page_sec_2 How does it work?
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41 */
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42
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43 #define T38_RX_BUF_LEN 2048
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44 #define T38_TX_BUF_LEN 16384
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45
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46 #define T38_TX_HDLC_BUFS 256
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47
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48 /* Make sure the HDLC frame buffers are big enough for ECM frames. */
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49 #define T38_MAX_HDLC_LEN 260
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50
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51 typedef struct
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52 {
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53 t38_core_state_t t38;
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54
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55 int ecm_allowed;
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56
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57 /*! \brief HDLC message buffers. */
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58 uint8_t hdlc_buf[T38_TX_HDLC_BUFS][T38_MAX_HDLC_LEN];
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59 /*! \brief HDLC message lengths. */
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60 int hdlc_len[T38_TX_HDLC_BUFS];
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61 /*! \brief HDLC message status flags. */
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62 int hdlc_flags[T38_TX_HDLC_BUFS];
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63 /*! \brief HDLC buffer contents. */
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64 int hdlc_contents[T38_TX_HDLC_BUFS];
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65 /*! \brief HDLC buffer number for input. */
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66 int hdlc_in;
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67 /*! \brief HDLC buffer number for output. */
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68 int hdlc_out;
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69
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70 /*! \brief Progressively calculated CRC for HDLC messaging received from a modem. */
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71 uint16_t crc;
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72
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73 /*! \brief non-ECM modem receive data buffer */
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74 uint8_t rx_data[T38_RX_BUF_LEN];
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75 int rx_data_ptr;
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76
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77 /*! \brief non-ECM modem transmit data buffer */
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78 uint8_t non_ecm_tx_data[T38_TX_BUF_LEN];
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79 int non_ecm_tx_in_ptr;
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80 int non_ecm_tx_out_ptr;
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81
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82 /*! \brief The location of the most recent EOL marker in the non-ECM data buffer */
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83 int non_ecm_tx_latest_eol_ptr;
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84 unsigned int bit_stream;
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85 /*! \brief The non-ECM flow control fill octet (0xFF before the first data, and 0x00
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86 once data has started). */
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87 uint8_t non_ecm_flow_control_fill_octet;
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88 /*! \brief TRUE if we are in the initial all ones part of non-ECM transmission. */
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89 int non_ecm_at_initial_all_ones;
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90 /*! \brief TRUE is the end of non-ECM data indication has been received. */
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91 int non_ecm_data_finished;
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92 /*! \brief The current octet being sent as non-ECM data. */
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93 int current_non_ecm_octet;
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94 /*! \brief The current bit number in the current non-ECM octet. */
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95 int non_ecm_bit_no;
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96 /*! \brief A count of the number of non-ECM fill octets generated for flow control control
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97 purposes. */
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98 int non_ecm_flow_control_fill_octets;
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99
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100 int current_rx_data_type;
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101 int current_rx_field_type;
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102 int current_rx_field_class;
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103 int in_progress_rx_indicator;
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104
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105 /*! \brief The current T.38 data type being sent. */
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106 int current_tx_data_type;
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107
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108 /*! \brief TRUE if we are in error correcting (ECM) mode */
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109 int ecm_mode;
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110 /*! \brief The current bit rate for the fast modem. */
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111 int fast_bit_rate;
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112 /*! \brief The current fast modem type. */
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113 int fast_modem;
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114 /*! \brief Use talker echo protection when transmitting. */
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115 int use_tep;
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116 /*! \brief TRUE if a carrier is present. Otherwise FALSE. */
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117 int rx_signal_present;
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118 /*! \brief TRUE if a modem has trained correctly. */
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119 int rx_trained;
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120
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121 /*! \brief A tone generator context used to generate supervisory tones during
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122 FAX handling. */
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123 tone_gen_state_t tone_gen;
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124 /*! \brief An HDLC context used when receiving HDLC messages. */
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125 hdlc_rx_state_t hdlcrx;
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126
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127 /*! \brief HDLC data used when transmitting HDLC messages. */
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128 hdlc_tx_state_t hdlctx;
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129
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130 /*! \brief A V.21 FSK modem context used when transmitting HDLC over V.21
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131 messages. */
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132 fsk_tx_state_t v21tx;
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133 /*! \brief A V.21 FSK modem context used when receiving HDLC over V.21
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134 messages. */
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135 fsk_rx_state_t v21rx;
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136
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137 #if defined(ENABLE_V17)
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138 /*! \brief A V.17 modem context used when sending FAXes at 7200bps, 9600bps
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139 12000bps or 14400bps*/
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140 v17_tx_state_t v17tx;
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141 /*! \brief A V.29 modem context used when receiving FAXes at 7200bps, 9600bps
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142 12000bps or 14400bps*/
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143 v17_rx_state_t v17rx;
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144 #endif
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145
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146 /*! \brief A V.29 modem context used when sending FAXes at 7200bps or
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147 9600bps */
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148 v29_tx_state_t v29tx;
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149 /*! \brief A V.29 modem context used when receiving FAXes at 7200bps or
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150 9600bps */
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151 v29_rx_state_t v29rx;
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152
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153 /*! \brief A V.27ter modem context used when sending FAXes at 2400bps or
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154 4800bps */
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155 v27ter_tx_state_t v27ter_tx;
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156 /*! \brief A V.27ter modem context used when receiving FAXes at 2400bps or
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157 4800bps */
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158 v27ter_rx_state_t v27ter_rx;
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159
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160 /*! \brief Used to insert timed silences. */
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161 silence_gen_state_t silence_gen;
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162
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163 /*! The current receive signal handler */
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164 span_rx_handler_t *rx_handler;
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165 void *rx_user_data;
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166
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167 /*! The current transmit signal handler */
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168 span_tx_handler_t *tx_handler;
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169 void *tx_user_data;
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170 /*! The transmit signal handler to be used when the current one has finished sending. */
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171 span_tx_handler_t *next_tx_handler;
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172 void *next_tx_user_data;
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173
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174 /*! The number of octets to send in each image packet (non-ECM or ECM) at the current
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175 rate and the current specified packet interval. */
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176 int octets_per_data_packet;
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177
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178 int v21_rx_active;
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179 int fast_rx_active;
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180 int samples_since_last_tx_packet;
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181 int octets_since_last_tx_packet;
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182 int short_train;
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183
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184 /*! \brief TRUE if we need to corrupt the HDLC frame in progress, so the receiver cannot
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185 interpret it. */
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186 int corrupt_the_frame;
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187
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188 int current_rx_type;
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189 int current_tx_type;
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190
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191 logging_state_t logging;
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192 } t38_gateway_state_t;
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193
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194 #ifdef __cplusplus
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195 extern "C" {
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196 #endif
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197
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198 /*! \brief Initialise a gateway mode T.38 context.
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199 \param s The T.38 context.
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200 \param tx_packet_handler A callback routine to encapsulate and transmit T.38 packets.
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201 \param tx_packet_user_data An opaque pointer passed to the tx_packet_handler routine.
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202 \return A pointer to the termination mode T.38 context, or NULL if there was a problem. */
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203 t38_gateway_state_t *t38_gateway_init(t38_gateway_state_t *s,
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204 t38_tx_packet_handler_t *tx_packet_handler,
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205 void *tx_packet_user_data);
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206
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207 /*! Process a block of received FAX audio samples.
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208 \brief Process a block of received FAX audio samples.
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209 \param s The T.38 context.
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210 \param amp The audio sample buffer.
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211 \param len The number of samples in the buffer.
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212 \return The number of samples unprocessed. */
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213 int t38_gateway_rx(t38_gateway_state_t *s, const int16_t *amp, int len);
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214
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215 /*! Generate a block of FAX audio samples.
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216 \brief Generate a block of FAX audio samples.
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217 \param s The T.38 context.
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218 \param amp The audio sample buffer.
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219 \param max_len The number of samples to be generated.
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220 \return The number of samples actually generated.
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221 */
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222 int t38_gateway_tx(t38_gateway_state_t *s, int16_t *amp, int max_len);
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223
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224 /*! Control whether error correcting mode (ECM) is allowed.
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225 \brief Control whether error correcting mode (ECM) is allowed.
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226 \param s The T.38 context.
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227 \param ecm_allowed TRUE is ECM is to be allowed.
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228 */
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229 void t38_gateway_ecm_control(t38_gateway_state_t *s, int ecm_allowed);
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230
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231 #ifdef __cplusplus
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232 }
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233 #endif
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234
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235 #endif
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236 /*- End of file ------------------------------------------------------------*/
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