spandsp  3.0.0
t38_core.h
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1 /*
2  * SpanDSP - a series of DSP components for telephony
3  *
4  * t38_core.h - An implementation of T.38, less the packet exchange part
5  *
6  * Written by Steve Underwood <steveu@coppice.org>
7  *
8  * Copyright (C) 2005 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_CORE_H_)
29 #define _SPANDSP_T38_CORE_H_
30 
31 /*! \page t38_core_page T.38 real time FAX over IP message handling
32 There are two ITU recommendations which address sending FAXes over IP networks. T.37 specifies a
33 method of encapsulating FAX images in e-mails, and transporting them to the recipient (an e-mail
34 box, or another FAX machine) in a store-and-forward manner. T.38 defines a protocol for
35 transmitting a FAX across an IP network in real time. The core T.38 modules implements the basic
36 message handling for the T.38, real time, FAX over IP (FoIP) protocol.
37 
38 The T.38 protocol can operate between:
39  - Internet-aware FAX terminals, which connect directly to an IP network. The T.38 terminal module
40  extends this module to provide a complete T.38 terminal.
41  - FAX gateways, which allow traditional PSTN FAX terminals to communicate through the Internet.
42  The T.38 gateway module extends this module to provide a T.38 gateway.
43  - A combination of terminals and gateways.
44 
45 T.38 is the only standardised protocol which exists for real-time FoIP. Reliably transporting a
46 FAX between PSTN FAX terminals, through an IP network, requires use of the T.38 protocol at FAX
47 gateways. VoIP connections are not robust for modem use, including FAX modem use. Most use low
48 bit rate codecs, which cannot convey the modem signals accurately. Even when high bit rate
49 codecs are used, VoIP connections suffer dropouts and timing adjustments, which modems cannot
50 tolerate. In a LAN environment the dropout rate may be very low, but the timing adjustments which
51 occur in VoIP connections still make modem operation unreliable. T.38 FAX gateways deal with the
52 delays, timing jitter, and packet loss experienced in packet networks, and isolate the PSTN FAX
53 terminals from these as far as possible. In addition, by sending FAXes as image data, rather than
54 digitised audio, they reduce the required bandwidth of the IP network.
55 
56 \section t38_core_page_sec_1 What does it do?
57 
58 \section t38_core_page_sec_2 How does it work?
59 
60 Timing differences and jitter between two T.38 entities can be a serious problem, if one of those
61 entities is a PSTN gateway.
62 
63 Flow control for non-ECM image data takes advantage of several features of the T.30 specification.
64 First, an unspecified number of 0xFF octets may be sent at the start of transmission. This means we
65 can add endless extra 0xFF bytes at this point, without breaking the T.30 spec. In practice, we
66 cannot add too many, or we will affect the timing tolerance of the T.30 protocol by delaying the
67 response at the end of each image. Secondly, just before an end of line (EOL) marker we can pad
68 with zero bits. Again, the number is limited only by need to avoid upsetting the timing of the
69 step following the non-ECM data.
70 */
71 
72 /*! T.38 indicator types */
74 {
75  T38_IND_NO_SIGNAL = 0,
76  T38_IND_CNG,
77  T38_IND_CED,
78  T38_IND_V21_PREAMBLE,
79  T38_IND_V27TER_2400_TRAINING,
80  T38_IND_V27TER_4800_TRAINING,
81  T38_IND_V29_7200_TRAINING,
82  T38_IND_V29_9600_TRAINING,
83  T38_IND_V17_7200_SHORT_TRAINING,
84  T38_IND_V17_7200_LONG_TRAINING,
85  T38_IND_V17_9600_SHORT_TRAINING,
86  T38_IND_V17_9600_LONG_TRAINING,
87  T38_IND_V17_12000_SHORT_TRAINING,
88  T38_IND_V17_12000_LONG_TRAINING,
89  T38_IND_V17_14400_SHORT_TRAINING,
90  T38_IND_V17_14400_LONG_TRAINING,
91  T38_IND_V8_ANSAM,
92  T38_IND_V8_SIGNAL,
93  T38_IND_V34_CNTL_CHANNEL_1200,
94  T38_IND_V34_PRI_CHANNEL,
95  T38_IND_V34_CC_RETRAIN,
96  T38_IND_V33_12000_TRAINING,
97  T38_IND_V33_14400_TRAINING
99 
100 /*! T.38 data types */
101 typedef enum t38_data_types_e
102 {
103  T38_DATA_NONE = -1,
104  T38_DATA_V21 = 0,
105  T38_DATA_V27TER_2400,
106  T38_DATA_V27TER_4800,
107  T38_DATA_V29_7200,
108  T38_DATA_V29_9600,
109  T38_DATA_V17_7200,
110  T38_DATA_V17_9600,
111  T38_DATA_V17_12000,
112  T38_DATA_V17_14400,
113  T38_DATA_V8,
114  T38_DATA_V34_PRI_RATE,
115  T38_DATA_V34_CC_1200,
116  T38_DATA_V34_PRI_CH,
117  T38_DATA_V33_12000,
118  T38_DATA_V33_14400
120 
121 /*! T.38 data field types */
122 typedef enum t38_field_types_e
123 {
124  T38_FIELD_HDLC_DATA = 0,
125  T38_FIELD_HDLC_SIG_END,
126  T38_FIELD_HDLC_FCS_OK,
127  T38_FIELD_HDLC_FCS_BAD,
128  T38_FIELD_HDLC_FCS_OK_SIG_END,
129  T38_FIELD_HDLC_FCS_BAD_SIG_END,
130  T38_FIELD_T4_NON_ECM_DATA,
131  T38_FIELD_T4_NON_ECM_SIG_END,
132  T38_FIELD_CM_MESSAGE,
133  T38_FIELD_JM_MESSAGE,
134  T38_FIELD_CI_MESSAGE,
135  T38_FIELD_V34RATE
137 
138 /*! T.38 field classes */
140 {
141  T38_FIELD_CLASS_NONE = 0,
142  T38_FIELD_CLASS_HDLC,
143  T38_FIELD_CLASS_NON_ECM
145 
146 /*! T.38 message types */
148 {
149  T38_TYPE_OF_MSG_T30_INDICATOR = 0,
150  T38_TYPE_OF_MSG_T30_DATA
152 
153 /*! T.38 transport types */
155 {
156  T38_TRANSPORT_UDPTL = 0,
157  T38_TRANSPORT_RTP,
158  T38_TRANSPORT_TCP,
159  T38_TRANSPORT_TCP_TPKT
161 
162 /*! T.38 TCF management types */
164 {
165  T38_DATA_RATE_MANAGEMENT_LOCAL_TCF = 1,
166  T38_DATA_RATE_MANAGEMENT_TRANSFERRED_TCF = 2
168 
169 /*! T.38 Packet categories used for setting the redundancy level and packet repeat
170  counts on a packet by packet basis. */
172 {
173  /*! \brief Indicator packet */
175  /*! \brief Control data packet */
177  /*! \brief Terminating control data packet */
179  /*! \brief Image data packet */
181  /*! \brief Terminating image data packet */
184 
186 {
187  /*! \brief The FCS at the end of an HDLC block can be send with the last chunk of the packet, or as a separate packet */
189  /*! \brief Send whole HDLC frames, rather than break them into mant packets for smooth analogue playout */
191  /*! \brief Allow for the time TEP takes when playing out the data */
193  /*! \brief Send regular indicators when idle, rather than a single shot as the idle period begins */
195  /*! \brief Send an indicator every 2s when idle */
197 } t38_chunking_mode_t;
198 
199 #define T38_RX_BUF_LEN 2048
200 #define T38_TX_BUF_LEN 16384
201 
202 /*! T.38 data field */
203 typedef struct
204 {
205  /*! Field type */
207  /*! Field contents */
208  const uint8_t *field;
209  /*! Field length */
212 
213 /*!
214  Core T.38 state, common to all modes of T.38.
215 */
217 
218 typedef int (*t38_tx_packet_handler_t)(t38_core_state_t *s, void *user_data, const uint8_t *buf, int len, int count);
219 
220 typedef int (*t38_rx_indicator_handler_t)(t38_core_state_t *s, void *user_data, int indicator);
221 typedef int (*t38_rx_data_handler_t)(t38_core_state_t *s, void *user_data, int data_type, int field_type, const uint8_t *buf, int len);
222 typedef int (*t38_rx_missing_handler_t)(t38_core_state_t *s, void *user_data, int rx_seq_no, int expected_seq_no);
223 
224 #if defined(__cplusplus)
225 extern "C"
226 {
227 #endif
228 
229 /*! \brief Convert the code for an indicator to a short text name.
230  \param indicator The type of indicator.
231  \return A pointer to a short text name for the indicator. */
232 SPAN_DECLARE(const char *) t38_indicator_to_str(int indicator);
233 
234 /*! \brief Convert the code for a type of data to a short text name.
235  \param data_type The data type.
236  \return A pointer to a short text name for the data type. */
237 SPAN_DECLARE(const char *) t38_data_type_to_str(int data_type);
238 
239 /*! \brief Convert the code for a type of data field to a short text name.
240  \param field_type The field type.
241  \return A pointer to a short text name for the field type. */
242 SPAN_DECLARE(const char *) t38_field_type_to_str(int field_type);
243 
244 /*! \brief Convert the code for a CM profile code to text description.
245  \param profile The profile code from a CM message.
246  \return A pointer to a short text description of the profile. */
247 SPAN_DECLARE(const char *) t38_cm_profile_to_str(int profile);
248 
249 /*! \brief Convert a JM message code to text description.
250  \param data The data field of the message.
251  \param len The length of the data field.
252  \return A pointer to a short text description of the profile. */
253 SPAN_DECLARE(const char *) t38_jm_to_str(const uint8_t *data, int len);
254 
255 /*! \brief Convert a V34rate message to an actual bit rate.
256  \param data The data field of the message.
257  \param len The length of the data field.
258  \return The bit rate, or -1 for a bad message. */
259 SPAN_DECLARE(int) t38_v34rate_to_bps(const uint8_t *data, int len);
260 
261 /*! \brief Send an indicator packet
262  \param s The T.38 context.
263  \param indicator The indicator to send.
264  \return The delay to allow after this indicator is sent. */
265 SPAN_DECLARE(int) t38_core_send_indicator(t38_core_state_t *s, int indicator);
266 
267 /*! \brief Find the delay to allow for HDLC flags after sending an indicator
268  \param s The T.38 context.
269  \param indicator The indicator to check.
270  \return The delay to allow for initial HDLC flags after this indicator is sent. */
271 SPAN_DECLARE(int) t38_core_send_flags_delay(t38_core_state_t *s, int indicator);
272 
273 /*! \brief Find the delay to allow for modem training after sending an indicator
274  \param s The T.38 context.
275  \param indicator The indicator to check.
276  \return The delay to allow for modem training after this indicator is sent. */
277 SPAN_DECLARE(int) t38_core_send_training_delay(t38_core_state_t *s, int indicator);
278 
279 /*! \brief Send a data packet
280  \param s The T.38 context.
281  \param data_type The packet's data type.
282  \param field_type The packet's field type.
283  \param field The message data content for the packet.
284  \param field_len The length of the message data, in bytes.
285  \param category The category of the packet being sent. This should be one of the values defined for t38_packet_categories_e.
286  \return 0 for OK, else -1 */
287 SPAN_DECLARE(int) t38_core_send_data(t38_core_state_t *s, int data_type, int field_type, const uint8_t field[], int field_len, int category);
288 
289 /*! \brief Send a data packet
290  \param s The T.38 context.
291  \param data_type The packet's data type.
292  \param field The list of fields.
293  \param fields The number of fields in the list.
294  \param category The category of the packet being sent. This should be one of the values defined for t38_packet_categories_e.
295  \return 0 for OK, else -1 */
296 SPAN_DECLARE(int) t38_core_send_data_multi_field(t38_core_state_t *s, int data_type, const t38_data_field_t field[], int fields, int category);
297 
298 /*! \brief Process a received T.38 IFP packet from an unreliable packet stream (e.g. UDPTL or RTP). This processing includes
299  packet sequence number checking, missing packet recovery, and skipping repeat packets.
300  \param s The T.38 context.
301  \param buf The packet contents.
302  \param len The length of the packet contents.
303  \param seq_no The packet sequence number.
304  \return 0 for OK, else -1. */
305 SPAN_DECLARE(int) t38_core_rx_ifp_packet(t38_core_state_t *s, const uint8_t *buf, int len, uint16_t seq_no);
306 
307 /*! \brief Process a received T.38 IFP packet from a reliable stream (e.g. TCP).
308  \param s The T.38 context.
309  \param buf The packet contents.
310  \param len The length of the packet contents.
311  \param seq_no The packet sequence number, used for logging purposes.
312  \return The length of the packet processed, or -1 if there is an error in the packet, or too few bytes of data to complete it. */
313 SPAN_DECLARE(int) t38_core_rx_ifp_stream(t38_core_state_t *s, const uint8_t *buf, int len, uint16_t log_seq_no);
314 
315 /*! Set the method to be used for data rate management, as per the T.38 spec.
316  \param s The T.38 context.
317  \param method 1 for pass TCF across the T.38 link, 2 for handle TCF locally.
318 */
319 SPAN_DECLARE(void) t38_set_data_rate_management_method(t38_core_state_t *s, int method);
320 
321 /*! Set the data transport protocol.
322  \param s The T.38 context.
323  \param data_transport_protocol UDPTL, RTP or TPKT.
324 */
326 
327 /*! Set the non-ECM fill bit removal mode.
328  \param s The T.38 context.
329  \param fill_bit_removal True to remove fill bits across the T.38 link.
330 */
331 SPAN_DECLARE(void) t38_set_fill_bit_removal(t38_core_state_t *s, bool fill_bit_removal);
332 
333 /*! Set the MMR transcoding mode.
334  \param s The T.38 context.
335  \param mmr_transcoding True to transcode to MMR across the T.38 link.
336 */
337 SPAN_DECLARE(void) t38_set_mmr_transcoding(t38_core_state_t *s, bool mmr_transcoding);
338 
339 /*! Set the JBIG transcoding mode.
340  \param s The T.38 context.
341  \param jbig_transcoding True to transcode to JBIG across the T.38 link.
342 */
343 SPAN_DECLARE(void) t38_set_jbig_transcoding(t38_core_state_t *s, bool jbig_transcoding);
344 
345 /*! Set the maximum buffer size for received data at the far end.
346  \param s The T.38 context.
347  \param max_buffer_size The maximum buffer size.
348 */
349 SPAN_DECLARE(void) t38_set_max_buffer_size(t38_core_state_t *s, int max_buffer_size);
350 
351 /*! Set the maximum size of an IFP packet that is acceptable by the far end.
352  \param s The T.38 context.
353  \param max_datagram_size The maximum IFP packet length, in bytes.
354 */
356 
357 /*! \brief Send a data packet
358  \param s The T.38 context.
359  \param category The category of the packet being sent. This should be one of the values defined for t38_packet_categories_e.
360  \param setting The repeat count for the category. This should be at least one for all categories other an indicator packets.
361  Zero is valid for indicator packets, as it suppresses the sending of indicator packets, as an application using
362  TCP for the transport would require. As the setting is passed through to the transmission channel, additional
363  information may be encoded in it, such as the redundancy depth for the particular packet category. */
364 SPAN_DECLARE(void) t38_set_redundancy_control(t38_core_state_t *s, int category, int setting);
365 
366 SPAN_DECLARE(void) t38_set_pace_transmission(t38_core_state_t *s, int pace_transmission);
367 
368 SPAN_DECLARE(void) t38_set_fastest_image_data_rate(t38_core_state_t *s, int max_rate);
369 
370 SPAN_DECLARE(int) t38_get_fastest_image_data_rate(t38_core_state_t *s);
371 
372 /*! Set the T.38 version to be emulated.
373  \param s The T.38 context.
374  \param t38_version Version number, as in the T.38 spec.
375 */
376 SPAN_DECLARE(void) t38_set_t38_version(t38_core_state_t *s, int t38_version);
377 
378 /*! Set the sequence number handling option.
379  \param s The T.38 context.
380  \param check True to check sequence numbers, and handle gaps reasonably. False
381  for no sequence number processing (e.g. for TPKT over TCP transport).
382 */
383 SPAN_DECLARE(void) t38_set_sequence_number_handling(t38_core_state_t *s, bool check);
384 
385 /*! Set the TEP handling option.
386  \param s The T.38 context.
387  \param allow_for_tep True to allow for TEP playout.
388 */
389 SPAN_DECLARE(void) t38_set_tep_handling(t38_core_state_t *s, bool allow_for_tep);
390 
391 /*! Set the time between packet transmissions.
392  \param s The T.38 context.
393  \param microseconds The time between packets in microseconds.
394 */
395 SPAN_DECLARE(void) t38_set_tx_packet_interval(t38_core_state_t *s, int microseconds);
396 
397 /*! Get the time between packet transmissions.
398  \param s The T.38 context.
399 */
400 SPAN_DECLARE(int) t38_get_tx_packet_interval(t38_core_state_t *s);
401 
402 /*! Get a pointer to the logging context associated with a T.38 context.
403  \brief Get a pointer to the logging context associated with a T.38 context.
404  \param s The T.38 context.
405  \return A pointer to the logging context, or NULL.
406 */
408 
409 /*! Restart a T.38 core context.
410  \brief Restart a T.38 core context.
411  \param s The T.38 context.
412  \return 0 for OK, else -1. */
413 SPAN_DECLARE(int) t38_core_restart(t38_core_state_t *s);
414 
415 /*! Initialise a T.38 core context.
416  \brief Initialise a T.38 core context.
417  \param s The T.38 context.
418  \param rx_indicator_handler Receive indicator handling routine.
419  \param rx_data_handler Receive data packet handling routine.
420  \param rx_rx_missing_handler Missing receive packet handling routine.
421  \param rx_packet_user_data An opaque pointer passed to the rx packet handling routines.
422  \param tx_packet_handler Packet transmit handling routine.
423  \param tx_packet_user_data An opaque pointer passed to the tx_packet_handler.
424  \return A pointer to the T.38 context, or NULL if there was a problem. */
426  t38_rx_indicator_handler_t rx_indicator_handler,
427  t38_rx_data_handler_t rx_data_handler,
428  t38_rx_missing_handler_t rx_missing_handler,
429  void *rx_user_data,
430  t38_tx_packet_handler_t tx_packet_handler,
431  void *tx_packet_user_data);
432 
433 /*! Release a signaling tone transmitter context.
434  \brief Release a signaling tone transmitter context.
435  \param s The T.38 context.
436  \return 0 for OK */
437 SPAN_DECLARE(int) t38_core_release(t38_core_state_t *s);
438 
439 /*! Free a signaling tone transmitter context.
440  \brief Free a signaling tone transmitter context.
441  \param s The T.38 context.
442  \return 0 for OK */
443 SPAN_DECLARE(int) t38_core_free(t38_core_state_t *s);
444 
445 #if defined(__cplusplus)
446 }
447 #endif
448 
449 #endif
450 /*- End of file ------------------------------------------------------------*/
enum t38_field_types_e t38_field_types_t
t38_chunking_mode_e
Definition: t38_core.h:185
void t38_set_sequence_number_handling(t38_core_state_t *s, bool check)
Definition: t38_core.c:1142
enum t38_transport_types_e t38_transport_types_t
int t38_core_restart(t38_core_state_t *s)
Restart a T.38 core context.
Definition: t38_core.c:1196
t38_rx_data_handler_t rx_data_handler
Handler routine to process received data packets.
Definition: private/t38_core.h:44
int data_transport_protocol
The emitting gateway may indicate a preference for either UDP/UDPTL, or UDP/RTP, or TCP for transport...
Definition: private/t38_core.h:70
Image data packet.
Definition: t38_core.h:180
int t38_core_send_indicator(t38_core_state_t *s, int indicator)
Send an indicator packet.
Definition: t38_core.c:979
t30_indicator_types_e
Definition: t38_core.h:73
enum t38_message_types_e t38_message_types_t
int t38_v34rate_to_bps(const uint8_t *data, int len)
Convert a V34rate message to an actual bit rate.
Definition: t38_core.c:292
t38_transport_types_e
Definition: t38_core.h:154
Terminating control data packet.
Definition: t38_core.h:178
const char * t38_field_type_to_str(int field_type)
Convert the code for a type of data field to a short text name.
Definition: t38_core.c:201
void t38_set_t38_version(t38_core_state_t *s, int t38_version)
Definition: t38_core.c:1136
void t38_set_tx_packet_interval(t38_core_state_t *s, int microseconds)
Definition: t38_core.c:1178
Definition: t38_core.h:203
Terminating image data packet.
Definition: t38_core.h:182
int t38_get_tx_packet_interval(t38_core_state_t *s)
Definition: t38_core.c:1184
int max_datagram_size
This option indicates the maximum size of a UDPTL packet or the maximum size of the payload within an...
Definition: private/t38_core.h:95
void t38_set_tep_handling(t38_core_state_t *s, bool allow_for_tep)
Definition: t38_core.c:1154
void * tx_packet_user_data
An opaque pointer passed to tx_packet_handler.
Definition: private/t38_core.h:39
Allow for the time TEP takes when playing out the data.
Definition: t38_core.h:192
const char * t38_jm_to_str(const uint8_t *data, int len)
Convert a JM message code to text description.
Definition: t38_core.c:257
int t38_version
This is the version number of ITU-T Rec. T.38. New versions shall be compatible with previous version...
Definition: private/t38_core.h:99
t38_field_classes_e
Definition: t38_core.h:139
int jbig_transcoding
Indicates the ability to convert to/from JBIG to reduce bandwidth.
Definition: private/t38_core.h:82
void t38_set_jbig_transcoding(t38_core_state_t *s, bool jbig_transcoding)
Definition: t38_core.c:1118
logging_state_t * t38_core_get_logging_state(t38_core_state_t *s)
Get a pointer to the logging context associated with a T.38 context.
Definition: t38_core.c:1190
const char * t38_data_type_to_str(int data_type)
Convert the code for a type of data to a short text name.
Definition: t38_core.c:161
void * rx_user_data
An opaque pointer passed to any of the above receive handling routines.
Definition: private/t38_core.h:48
int field_type
Definition: t38_core.h:206
enum t38_packet_categories_e t38_packet_categories_t
t38_tx_packet_handler_t tx_packet_handler
Handler routine to transmit IFP packets generated by the T.38 protocol engine.
Definition: private/t38_core.h:37
int field_len
Definition: t38_core.h:210
const char * t38_indicator_to_str(int indicator)
Convert the code for an indicator to a short text name.
Definition: t38_core.c:105
Control data packet.
Definition: t38_core.h:176
enum t30_indicator_types_e t30_indicator_types_t
void t38_set_mmr_transcoding(t38_core_state_t *s, bool mmr_transcoding)
Definition: t38_core.c:1112
t38_data_rate_management_types_e
Definition: t38_core.h:163
int t38_core_send_flags_delay(t38_core_state_t *s, int indicator)
Find the delay to allow for HDLC flags after sending an indicator.
Definition: t38_core.c:1028
int pace_transmission
Pace transmission.
Definition: private/t38_core.h:108
void t38_set_fill_bit_removal(t38_core_state_t *s, bool fill_bit_removal)
Definition: t38_core.c:1106
void t38_set_max_buffer_size(t38_core_state_t *s, int max_buffer_size)
Definition: t38_core.c:1124
const uint8_t * field
Definition: t38_core.h:208
t38_packet_categories_e
Definition: t38_core.h:171
int fill_bit_removal
Indicates the capability to remove and insert fill bits in Phase C, non-ECM data to reduce bandwidth ...
Definition: private/t38_core.h:74
Definition: private/logging.h:33
int t38_core_free(t38_core_state_t *s)
Free a signaling tone transmitter context.
Definition: t38_core.c:1274
t38_rx_indicator_handler_t rx_indicator_handler
Handler routine to process received indicator packets.
Definition: private/t38_core.h:42
void t38_set_redundancy_control(t38_core_state_t *s, int category, int setting)
Send a data packet.
Definition: t38_core.c:1160
const char * t38_cm_profile_to_str(int profile)
Convert the code for a CM profile code to text description.
Definition: t38_core.c:235
int mmr_transcoding
Indicates the ability to convert to/from MMR from/to the line format to improve the compression of th...
Definition: private/t38_core.h:79
int max_buffer_size
For UDP (UDPTL or RTP) modes, this option indicates the maximum number of octets that can be stored o...
Definition: private/t38_core.h:90
int t38_core_rx_ifp_stream(t38_core_state_t *s, const uint8_t *buf, int len, uint16_t log_seq_no)
Process a received T.38 IFP packet from a reliable stream (e.g. TCP).
Definition: t38_core.c:356
void t38_set_data_rate_management_method(t38_core_state_t *s, int method)
Definition: t38_core.c:1094
t38_core_state_t * t38_core_init(t38_core_state_t *s, t38_rx_indicator_handler_t rx_indicator_handler, t38_rx_data_handler_t rx_data_handler, t38_rx_missing_handler_t rx_missing_handler, void *rx_user_data, t38_tx_packet_handler_t tx_packet_handler, void *tx_packet_user_data)
Initialise a T.38 core context.
Definition: t38_core.c:1216
int t38_core_rx_ifp_packet(t38_core_state_t *s, const uint8_t *buf, int len, uint16_t seq_no)
Process a received T.38 IFP packet from an unreliable packet stream (e.g. UDPTL or RTP)...
Definition: t38_core.c:679
enum t38_field_classes_e t38_field_classes_t
enum t38_data_rate_management_types_e t38_data_rate_management_types_t
int allow_for_tep
Allow time for TEP playout.
Definition: private/t38_core.h:102
Send an indicator every 2s when idle.
Definition: t38_core.h:196
Send whole HDLC frames, rather than break them into mant packets for smooth analogue playout...
Definition: t38_core.h:190
t38_field_types_e
Definition: t38_core.h:122
void t38_set_data_transport_protocol(t38_core_state_t *s, int data_transport_protocol)
Definition: t38_core.c:1100
void t38_set_max_datagram_size(t38_core_state_t *s, int max_datagram_size)
Definition: t38_core.c:1130
int t38_core_send_training_delay(t38_core_state_t *s, int indicator)
Find the delay to allow for modem training after sending an indicator.
Definition: t38_core.c:1037
Definition: private/t38_core.h:34
t38_rx_missing_handler_t rx_missing_handler
Handler routine to process the missing packet condition.
Definition: private/t38_core.h:46
t38_message_types_e
Definition: t38_core.h:147
int t38_core_release(t38_core_state_t *s)
Release a signaling tone transmitter context.
Definition: t38_core.c:1268
int t38_core_send_data_multi_field(t38_core_state_t *s, int data_type, const t38_data_field_t field[], int fields, int category)
Send a data packet.
Definition: t38_core.c:1072
t38_data_types_e
Definition: t38_core.h:101
Send regular indicators when idle, rather than a single shot as the idle period begins.
Definition: t38_core.h:194
Indicator packet.
Definition: t38_core.h:174
enum t38_data_types_e t38_data_types_t
int t38_core_send_data(t38_core_state_t *s, int data_type, int field_type, const uint8_t field[], int field_len, int category)
Send a data packet.
Definition: t38_core.c:1046
The FCS at the end of an HDLC block can be send with the last chunk of the packet, or as a separate packet.
Definition: t38_core.h:188