spandsp: t38_gateway.h Source File

spandsp 0.0.6

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 receive buffer length */
42#define T38_RX_BUF_LEN 2048
43/*! The number of HDLC transmit buffers */
44#define T38_TX_HDLC_BUFS 256
45/*! The maximum length of an HDLC frame buffer. This must be big enough for ECM frames. */
46#define T38_MAX_HDLC_LEN 260
47
48typedef struct t38_gateway_state_s t38_gateway_state_t;
49
50/*!
51 T.30 real time frame handler.
52 \brief T.30 real time frame handler.
53 \param s The T.30 context.
54 \param user_data An opaque pointer.
55 \param direction TRUE for incoming, FALSE for outgoing.
56 \param msg The HDLC message.
57 \param len The length of the message.
58*/
59 typedef void (t38_gateway_real_time_frame_handler_t)(t38_gateway_state_t *s,
60 void *user_data,
61 int direction,
62 const uint8_t *msg,
63 int len);
64
65/*!
66 T.38 gateway results.
67 */
68 typedef struct
69{
70 /*! \brief The current bit rate for image transfer. */
71 int bit_rate;
72 /*! \brief TRUE if error correcting mode is used. */
73 int error_correcting_mode;
74 /*! \brief The number of pages transferred so far. */
75 int pages_transferred;
76} t38_stats_t;
77
78#if defined(__cplusplus)
79extern "C"
80{
81#endif
82
83/*! \brief Initialise a gateway mode T.38 context.
84 \param s The T.38 context.
85 \param tx_packet_handler A callback routine to encapsulate and transmit T.38 packets.
86 \param tx_packet_user_data An opaque pointer passed to the tx_packet_handler routine.
87 \return A pointer to the termination mode T.38 context, or NULL if there was a problem. */
88SPAN_DECLARE(t38_gateway_state_t *) t38_gateway_init(t38_gateway_state_t *s,
89 t38_tx_packet_handler_t *tx_packet_handler,
90 void *tx_packet_user_data);
91
92/*! Release a gateway mode T.38 context.
93 \brief Release a T.38 context.
94 \param s The T.38 context.
95 \return 0 for OK, else -1. */
96SPAN_DECLARE(int) t38_gateway_release(t38_gateway_state_t *s);
97
98/*! Free a gateway mode T.38 context.
99 \brief Free a T.38 context.
100 \param s The T.38 context.
101 \return 0 for OK, else -1. */
102SPAN_DECLARE(int) t38_gateway_free(t38_gateway_state_t *s);
103
104/*! Process a block of received FAX audio samples.
105 \brief Process a block of received FAX audio samples.
106 \param s The T.38 context.
107 \param amp The audio sample buffer.
108 \param len The number of samples in the buffer.
109 \return The number of samples unprocessed. */
110SPAN_DECLARE_NONSTD(int) t38_gateway_rx(t38_gateway_state_t *s, int16_t amp[], int len);
111
112/*! Apply fake processing when a block of audio samples is missing (e.g due
113 to packet loss).
114 \brief Apply fake received audio processing.
115 \param s The T.38 context.
116 \param len The number of samples to fake.
117 \return The number of samples unprocessed. This should only be non-zero if
118 the software has reached the end of the FAX call.
119*/
120SPAN_DECLARE_NONSTD(int) t38_gateway_rx_fillin(t38_gateway_state_t *s, int len);
121
122/*! Generate a block of FAX audio samples.
123 \brief Generate a block of FAX audio samples.
124 \param s The T.38 context.
125 \param amp The audio sample buffer.
126 \param max_len The number of samples to be generated.
127 \return The number of samples actually generated.
128*/
129SPAN_DECLARE_NONSTD(int) t38_gateway_tx(t38_gateway_state_t *s, int16_t amp[], int max_len);
130
131/*! Control whether error correcting mode (ECM) is allowed.
132 \brief Control whether error correcting mode (ECM) is allowed.
133 \param s The T.38 context.
134 \param ecm_allowed TRUE is ECM is to be allowed.
135*/
136SPAN_DECLARE(void) t38_gateway_set_ecm_capability(t38_gateway_state_t *s, int ecm_allowed);
137
138/*! Select whether silent audio will be sent when transmit is idle.
139 \brief Select whether silent audio will be sent when transmit is idle.
140 \param s The T.38 context.
141 \param transmit_on_idle TRUE if silent audio should be output when the FAX transmitter is
142 idle. FALSE to transmit zero length audio when the FAX transmitter is idle. The default
143 behaviour is FALSE.
144*/
145SPAN_DECLARE(void) t38_gateway_set_transmit_on_idle(t38_gateway_state_t *s, int transmit_on_idle);
146
147/*! Specify which modem types are supported by a T.30 context.
148 \brief Specify supported modems.
149 \param s The T.38 context.
150 \param supported_modems Bit field list of the supported modems.
151*/
152SPAN_DECLARE(void) t38_gateway_set_supported_modems(t38_gateway_state_t *s, int supported_modems);
153
154/*! Select whether NSC, NSF, and NSS should be suppressed. It selected, the contents of
155 these messages are forced to zero for all octets beyond the message type. This makes
156 them look like manufacturer specific messages, from a manufacturer which does not exist.
157 \brief Select whether NSC, NSF, and NSS should be suppressed.
158 \param s The T.38 context.
159 \param from_t38 A string of bytes to overwrite the header of any NSC, NSF, and NSS
160 frames passing through the gateway from T.38 the the modem.
161 \param from_t38_len The length of the overwrite string.
162 \param from_modem A string of bytes to overwrite the header of any NSC, NSF, and NSS
163 frames passing through the gateway from the modem to T.38.
164 \param from_modem_len The length of the overwrite string.
165*/
166SPAN_DECLARE(void) t38_gateway_set_nsx_suppression(t38_gateway_state_t *s,
167 const uint8_t *from_t38,
168 int from_t38_len,
169 const uint8_t *from_modem,
170 int from_modem_len);
171
172/*! Select whether talker echo protection tone will be sent for the image modems.
173 \brief Select whether TEP will be sent for the image modems.
174 \param s The T.38 context.
175 \param use_tep TRUE if TEP should be sent.
176*/
177SPAN_DECLARE(void) t38_gateway_set_tep_mode(t38_gateway_state_t *s, int use_tep);
178
179/*! Select whether non-ECM fill bits are to be removed during transmission.
180 \brief Select whether non-ECM fill bits are to be removed during transmission.
181 \param s The T.38 context.
182 \param remove TRUE if fill bits are to be removed.
183*/
184SPAN_DECLARE(void) t38_gateway_set_fill_bit_removal(t38_gateway_state_t *s, int remove);
185
186/*! Get the current transfer statistics for the current T.38 session.
187 \brief Get the current transfer statistics.
188 \param s The T.38 context.
189 \param t A pointer to a buffer for the statistics. */
190SPAN_DECLARE(void) t38_gateway_get_transfer_statistics(t38_gateway_state_t *s, t38_stats_t *t);
191
192/*! Get a pointer to the T.38 core IFP packet engine associated with a
193 gateway mode T.38 context.
194 \brief Get a pointer to the T.38 core IFP packet engine associated
195 with a T.38 context.
196 \param s The T.38 context.
197 \return A pointer to the T.38 core context, or NULL.
198*/
199SPAN_DECLARE(t38_core_state_t *) t38_gateway_get_t38_core_state(t38_gateway_state_t *s);
200
201/*! Get a pointer to the logging context associated with a T.38 context.
202 \brief Get a pointer to the logging context associated with a T.38 context.
203 \param s The T.38 context.
204 \return A pointer to the logging context, or NULL.
205*/
206SPAN_DECLARE(logging_state_t *) t38_gateway_get_logging_state(t38_gateway_state_t *s);
207
208/*! Set a callback function for T.30 frame exchange monitoring. This is called from the heart
209 of the signal processing, so don't take too long in the handler routine.
210 \brief Set a callback function for T.30 frame exchange monitoring.
211 \param s The T.30 context.
212 \param handler The callback function.
213 \param user_data An opaque pointer passed to the callback function. */
214SPAN_DECLARE(void) t38_gateway_set_real_time_frame_handler(t38_gateway_state_t *s,
215 t38_gateway_real_time_frame_handler_t *handler,
216 void *user_data);
217
218#if defined(__cplusplus)
219}
220#endif
221
222#endif
223/*- End of file ------------------------------------------------------------*/
logging_state_s
Definition private/logging.h:34
t38_core_state_s
Definition private/t38_core.h:33
t38_gateway_state_s
Definition private/t38_gateway.h:195
t38_stats_t
Definition t38_gateway.h:69
t38_stats_t::error_correcting_mode
int error_correcting_mode
TRUE if error correcting mode is used.
Definition t38_gateway.h:73
t38_stats_t::bit_rate
int bit_rate
The current bit rate for image transfer.
Definition t38_gateway.h:71
t38_stats_t::pages_transferred
int pages_transferred
The number of pages transferred so far.
Definition t38_gateway.h:75
t38_gateway_real_time_frame_handler_t
void() t38_gateway_real_time_frame_handler_t(t38_gateway_state_t *s, void *user_data, int direction, const uint8_t *msg, int len)
T.30 real time frame handler.
Definition t38_gateway.h:59
t38_gateway_release
int t38_gateway_release(t38_gateway_state_t *s)
Release a T.38 context.
Definition t38_gateway.c:2560
t38_gateway_set_supported_modems
void t38_gateway_set_supported_modems(t38_gateway_state_t *s, int supported_modems)
Specify supported modems.
Definition t38_gateway.c:2404
t38_gateway_free
int t38_gateway_free(t38_gateway_state_t *s)
Free a T.38 context.
Definition t38_gateway.c:2566
t38_gateway_get_logging_state
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:2386
t38_gateway_set_transmit_on_idle
void t38_gateway_set_transmit_on_idle(t38_gateway_state_t *s, int transmit_on_idle)
Select whether silent audio will be sent when transmit is idle.
Definition t38_gateway.c:2398
t38_gateway_set_nsx_suppression
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:2417
t38_gateway_init
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:2494
t38_gateway_set_ecm_capability
void t38_gateway_set_ecm_capability(t38_gateway_state_t *s, int ecm_allowed)
Control whether error correcting mode (ECM) is allowed.
Definition t38_gateway.c:2392
t38_gateway_set_fill_bit_removal
void t38_gateway_set_fill_bit_removal(t38_gateway_state_t *s, int remove)
Select whether non-ECM fill bits are to be removed during transmission.
Definition t38_gateway.c:2434
t38_gateway_set_tep_mode
void t38_gateway_set_tep_mode(t38_gateway_state_t *s, int use_tep)
Select whether TEP will be sent for the image modems.
Definition t38_gateway.c:2428
t38_gateway_get_transfer_statistics
void t38_gateway_get_transfer_statistics(t38_gateway_state_t *s, t38_stats_t *t)
Get the current transfer statistics.
Definition t38_gateway.c:2371
t38_gateway_set_real_time_frame_handler
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:2440
t38_gateway_get_t38_core_state
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:2380