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 
34 The T.38 gateway facility provides a robust interface between T.38 IP packet streams and
35 and 8k samples/second audio streams. It provides the buffering and flow control features needed
36 to 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 
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 */
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. */
74  /*! \brief The number of pages transferred so far. */
76 } t38_stats_t;
77 
78 #if defined(__cplusplus)
79 extern "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. */
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. */
96 SPAN_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. */
102 SPAN_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. */
110 SPAN_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 */
120 SPAN_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 */
129 SPAN_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 */
136 SPAN_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 */
145 SPAN_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 */
152 SPAN_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 */
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 */
177 SPAN_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 */
184 SPAN_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. */
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 */
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 */
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. */
216  void *user_data);
217 
218 #if defined(__cplusplus)
219 }
220 #endif
221 
222 #endif
223 /*- End of file ------------------------------------------------------------*/
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
int t38_gateway_release(t38_gateway_state_t *s)
Release a T.38 context.
Definition: t38_gateway.c:2560
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
int t38_gateway_free(t38_gateway_state_t *s)
Free a T.38 context.
Definition: t38_gateway.c:2566
int bit_rate
The current bit rate for image transfer.
Definition: t38_gateway.h:71
SPAN_DECLARE_NONSTD(int) t38_gateway_rx(t38_gateway_state_t *s
Process a block of received FAX audio samples.
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
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
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
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
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
Definition: t38_gateway.h:68
Definition: private/logging.h:33
int error_correcting_mode
TRUE if error correcting mode is used.
Definition: t38_gateway.h:73
Definition: private/t38_gateway.h:194
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
int pages_transferred
The number of pages transferred so far.
Definition: t38_gateway.h:75
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_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
Definition: private/t38_core.h:32
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
void t38_gateway_set_supported_modems(t38_gateway_state_t *s, int supported_modems)
Specify supported modems.
Definition: t38_gateway.c:2404