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 1.59 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 ------------------------------------------------------------*/

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