t38_gateway.h

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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 1.63 2009/04/12 09:12:10 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 /*! The receive buffer length */
00044 #define T38_RX_BUF_LEN          2048
00045 /*! The number of HDLC transmit buffers */
00046 #define T38_TX_HDLC_BUFS        256
00047 /*! The maximum length of an HDLC frame buffer. This must be big enough for ECM frames. */
00048 #define T38_MAX_HDLC_LEN        260
00049 
00050 typedef struct t38_gateway_state_s t38_gateway_state_t;
00051 
00052 /*!
00053     T.30 real time frame handler.
00054     \brief T.30 real time frame handler.
00055     \param s The T.30 context.
00056     \param user_data An opaque pointer.
00057     \param direction TRUE for incoming, FALSE for outgoing.
00058     \param msg The HDLC message.
00059     \param len The length of the message.
00060 */
00061 typedef void (t38_gateway_real_time_frame_handler_t)(t38_gateway_state_t *s,
00062                                                      void *user_data,
00063                                                      int direction,
00064                                                      const uint8_t *msg,
00065                                                      int len);
00066 
00067 /*!
00068     T.38 gateway results.
00069  */
00070 typedef struct
00071 {
00072     /*! \brief The current bit rate for image transfer. */
00073     int bit_rate;
00074     /*! \brief TRUE if error correcting mode is used. */
00075     int error_correcting_mode;
00076     /*! \brief The number of pages transferred so far. */
00077     int pages_transferred;
00078 } t38_stats_t;
00079 
00080 #if defined(__cplusplus)
00081 extern "C"
00082 {
00083 #endif
00084 
00085 /*! \brief Initialise a gateway mode T.38 context.
00086     \param s The T.38 context.
00087     \param tx_packet_handler A callback routine to encapsulate and transmit T.38 packets.
00088     \param tx_packet_user_data An opaque pointer passed to the tx_packet_handler routine.
00089     \return A pointer to the termination mode T.38 context, or NULL if there was a problem. */
00090 SPAN_DECLARE(t38_gateway_state_t *) t38_gateway_init(t38_gateway_state_t *s,
00091                                                      t38_tx_packet_handler_t *tx_packet_handler,
00092                                                      void *tx_packet_user_data);
00093 
00094 /*! Release a gateway mode T.38 context.
00095     \brief Release a T.38 context.
00096     \param s The T.38 context.
00097     \return 0 for OK, else -1. */
00098 SPAN_DECLARE(int) t38_gateway_release(t38_gateway_state_t *s);
00099 
00100 /*! Free a gateway mode T.38 context.
00101     \brief Free a T.38 context.
00102     \param s The T.38 context.
00103     \return 0 for OK, else -1. */
00104 SPAN_DECLARE(int) t38_gateway_free(t38_gateway_state_t *s);
00105 
00106 /*! Process a block of received FAX audio samples.
00107     \brief Process a block of received FAX audio samples.
00108     \param s The T.38 context.
00109     \param amp The audio sample buffer.
00110     \param len The number of samples in the buffer.
00111     \return The number of samples unprocessed. */
00112 SPAN_DECLARE(int) t38_gateway_rx(t38_gateway_state_t *s, int16_t amp[], int len);
00113 
00114 /*! Generate a block of FAX audio samples.
00115     \brief Generate a block of FAX audio samples.
00116     \param s The T.38 context.
00117     \param amp The audio sample buffer.
00118     \param max_len The number of samples to be generated.
00119     \return The number of samples actually generated.
00120 */
00121 SPAN_DECLARE(int) t38_gateway_tx(t38_gateway_state_t *s, int16_t amp[], int max_len);
00122 
00123 /*! Control whether error correcting mode (ECM) is allowed.
00124     \brief Control whether error correcting mode (ECM) is allowed.
00125     \param s The T.38 context.
00126     \param ecm_allowed TRUE is ECM is to be allowed.
00127 */
00128 SPAN_DECLARE(void) t38_gateway_set_ecm_capability(t38_gateway_state_t *s, int ecm_allowed);
00129 
00130 /*! Select whether silent audio will be sent when transmit is idle.
00131     \brief Select whether silent audio will be sent when transmit is idle.
00132     \param s The T.38 context.
00133     \param transmit_on_idle TRUE if silent audio should be output when the FAX transmitter is
00134            idle. FALSE to transmit zero length audio when the FAX transmitter is idle. The default
00135            behaviour is FALSE.
00136 */
00137 SPAN_DECLARE(void) t38_gateway_set_transmit_on_idle(t38_gateway_state_t *s, int transmit_on_idle);
00138 
00139 /*! Specify which modem types are supported by a T.30 context.
00140     \brief Specify supported modems.
00141     \param s The T.38 context.
00142     \param supported_modems Bit field list of the supported modems.
00143 */
00144 SPAN_DECLARE(void) t38_gateway_set_supported_modems(t38_gateway_state_t *s, int supported_modems);
00145 
00146 /*! Select whether NSC, NSF, and NSS should be suppressed. It selected, the contents of
00147     these messages are forced to zero for all octets beyond the message type. This makes
00148     them look like manufacturer specific messages, from a manufacturer which does not exist.
00149     \brief Select whether NSC, NSF, and NSS should be suppressed.
00150     \param s The T.38 context.
00151     \param from_t38 A string of bytes to overwrite the header of any NSC, NSF, and NSS
00152            frames passing through the gateway from T.38 the the modem.
00153     \param from_t38_len The length of the overwrite string.
00154     \param from_modem A string of bytes to overwrite the header of any NSC, NSF, and NSS
00155            frames passing through the gateway from the modem to T.38.
00156     \param from_modem_len The length of the overwrite string.
00157 */
00158 SPAN_DECLARE(void) t38_gateway_set_nsx_suppression(t38_gateway_state_t *s,
00159                                                    const uint8_t *from_t38,
00160                                                    int from_t38_len,
00161                                                    const uint8_t *from_modem,
00162                                                    int from_modem_len);
00163 
00164 /*! Select whether talker echo protection tone will be sent for the image modems.
00165     \brief Select whether TEP will be sent for the image modems.
00166     \param s The T.38 context.
00167     \param use_tep TRUE if TEP should be sent.
00168 */
00169 SPAN_DECLARE(void) t38_gateway_set_tep_mode(t38_gateway_state_t *s, int use_tep);
00170 
00171 /*! Select whether non-ECM fill bits are to be removed during transmission.
00172     \brief Select whether non-ECM fill bits are to be removed during transmission.
00173     \param s The T.38 context.
00174     \param remove TRUE if fill bits are to be removed.
00175 */
00176 SPAN_DECLARE(void) t38_gateway_set_fill_bit_removal(t38_gateway_state_t *s, int remove);
00177 
00178 /*! Get the current transfer statistics for the current T.38 session.
00179     \brief Get the current transfer statistics.
00180     \param s The T.38 context.
00181     \param t A pointer to a buffer for the statistics. */
00182 SPAN_DECLARE(void) t38_gateway_get_transfer_statistics(t38_gateway_state_t *s, t38_stats_t *t);
00183 
00184 /*! Get a pointer to the T.38 core IFP packet engine associated with a
00185     gateway mode T.38 context.
00186     \brief Get a pointer to the T.38 core IFP packet engine associated
00187            with a T.38 context.
00188     \param s The T.38 context.
00189     \return A pointer to the T.38 core context, or NULL.
00190 */
00191 SPAN_DECLARE(t38_core_state_t *) t38_gateway_get_t38_core_state(t38_gateway_state_t *s);
00192 
00193 /*! Get a pointer to the logging context associated with a T.38 context.
00194     \brief Get a pointer to the logging context associated with a T.38 context.
00195     \param s The T.38 context.
00196     \return A pointer to the logging context, or NULL.
00197 */
00198 SPAN_DECLARE(logging_state_t *) t38_gateway_get_logging_state(t38_gateway_state_t *s);
00199 
00200 /*! Set a callback function for T.30 frame exchange monitoring. This is called from the heart
00201     of the signal processing, so don't take too long in the handler routine.
00202     \brief Set a callback function for T.30 frame exchange monitoring.
00203     \param s The T.30 context.
00204     \param handler The callback function.
00205     \param user_data An opaque pointer passed to the callback function. */
00206 SPAN_DECLARE(void) t38_gateway_set_real_time_frame_handler(t38_gateway_state_t *s,
00207                                                            t38_gateway_real_time_frame_handler_t *handler,
00208                                                            void *user_data);
00209 
00210 #if defined(__cplusplus)
00211 }
00212 #endif
00213 
00214 #endif
00215 /*- End of file ------------------------------------------------------------*/

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