spandsp 3.0.0
t38_gateway.h
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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
34The T.38 gateway facility provides a robust interface between T.38 IP packet streams and
35and 8k samples/second audio streams. It provides the buffering and flow control features needed
36to 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
45typedef 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*/
55typedef 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 */
63typedef struct
64{
65 /*! \brief The current bit rate for image transfer. */
67 /*! \brief True if error correcting mode is used. */
69 /*! \brief The number of pages transferred so far. */
72
73#if defined(__cplusplus)
74extern "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. */
83SPAN_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. */
91SPAN_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. */
97SPAN_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. */
105SPAN_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*/
115SPAN_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*/
124SPAN_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*/
131SPAN_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*/
140SPAN_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*/
147SPAN_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*/
161SPAN_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*/
172SPAN_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*/
179SPAN_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. */
185SPAN_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*/
194SPAN_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*/
201SPAN_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. */
209SPAN_DECLARE(void) t38_gateway_set_real_time_frame_handler(t38_gateway_state_t *s,
211 void *user_data);
212
213#if defined(__cplusplus)
214}
215#endif
216
217#endif
218/*- End of file ------------------------------------------------------------*/
struct logging_state_s logging_state_t
Definition logging.h:72
Definition private/t38_gateway.h:192
Definition t38_gateway.h:64
bool error_correcting_mode
True if error correcting mode is used.
Definition t38_gateway.h:68
int bit_rate
The current bit rate for image transfer.
Definition t38_gateway.h:66
int pages_transferred
The number of pages transferred so far.
Definition t38_gateway.h:70
struct t38_core_state_s t38_core_state_t
Definition t38_core.h:202
int t38_gateway_release(t38_gateway_state_t *s)
Release a T.38 context.
Definition t38_gateway.c:2423
void t38_gateway_set_supported_modems(t38_gateway_state_t *s, int supported_modems)
Specify supported modems.
Definition t38_gateway.c:2262
int t38_gateway_free(t38_gateway_state_t *s)
Free a T.38 context.
Definition t38_gateway.c:2429
logging_state_t * t38_gateway_get_logging_state(t38_gateway_state_t *s)
Get a pointer to the logging context associated with a T.38 context.
Definition t38_gateway.c:2244
void t38_gateway_set_transmit_on_idle(t38_gateway_state_t *s, bool transmit_on_idle)
Select whether silent audio will be sent when transmit is idle.
Definition t38_gateway.c:2256
t38_gateway_state_t * t38_gateway_init(t38_gateway_state_t *s, t38_tx_packet_handler_t tx_packet_handler, void *tx_packet_user_data)
Initialise a gateway mode T.38 context.
Definition t38_gateway.c:2357
void t38_gateway_set_nsx_suppression(t38_gateway_state_t *s, const uint8_t *from_t38, int from_t38_len, const uint8_t *from_modem, int from_modem_len)
Select whether NSC, NSF, and NSS should be suppressed.
Definition t38_gateway.c:2275
int t38_gateway_tx(t38_gateway_state_t *s, int16_t amp[], int max_len)
Generate a block of FAX audio samples.
Definition t38_gateway.c:2184
void t38_gateway_set_tep_mode(t38_gateway_state_t *s, bool use_tep)
Select whether TEP will be sent for the image modems.
Definition t38_gateway.c:2292
void t38_gateway_set_real_time_frame_handler(t38_gateway_state_t *s, t38_gateway_real_time_frame_handler_t handler, void *user_data)
Set a callback function for T.30 frame exchange monitoring.
Definition t38_gateway.c:2304
void t38_gateway_set_fill_bit_removal(t38_gateway_state_t *s, bool remove)
Select whether non-ECM fill bits are to be removed during transmission.
Definition t38_gateway.c:2298
void t38_gateway_set_ecm_capability(t38_gateway_state_t *s, bool ecm_allowed)
Control whether error correcting mode (ECM) is allowed.
Definition t38_gateway.c:2250
void(* t38_gateway_real_time_frame_handler_t)(void *user_data, bool incoming, const uint8_t *msg, int len)
T.38 gateway real time frame handler.
Definition t38_gateway.h:55
int t38_gateway_rx_fillin(t38_gateway_state_t *s, int len)
Apply fake received audio processing.
Definition t38_gateway.c:2156
int t38_gateway_rx(t38_gateway_state_t *s, int16_t amp[], int len)
Process a block of received FAX audio samples.
Definition t38_gateway.c:2137
void t38_gateway_get_transfer_statistics(t38_gateway_state_t *s, t38_stats_t *t)
Get the current transfer statistics.
Definition t38_gateway.c:2229
t38_core_state_t * t38_gateway_get_t38_core_state(t38_gateway_state_t *s)
Get a pointer to the T.38 core IFP packet engine associated with a T.38 context.
Definition t38_gateway.c:2238