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comparison spandsp-0.0.6pre17/src/spandsp/t38_core.h @ 4:26cd8f1ef0b1

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import spandsp-0.0.6pre17
author Peter Meerwald <pmeerw@cosy.sbg.ac.at>
date Fri, 25 Jun 2010 15:50:58 +0200
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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 * $Id: t38_core.h,v 1.39 2009/07/14 13:54:22 steveu Exp $
26 */
27
28 /*! \file */
29
30 #if !defined(_SPANDSP_T38_CORE_H_)
31 #define _SPANDSP_T38_CORE_H_
32
33 /*! \page t38_core_page T.38 real time FAX over IP message handling
34 There are two ITU recommendations which address sending FAXes over IP networks. T.37 specifies a
35 method of encapsulating FAX images in e-mails, and transporting them to the recipient (an e-mail
36 box, or another FAX machine) in a store-and-forward manner. T.38 defines a protocol for
37 transmitting a FAX across an IP network in real time. The core T.38 modules implements the basic
38 message handling for the T.38, real time, FAX over IP (FoIP) protocol.
39
40 The T.38 protocol can operate between:
41 - Internet-aware FAX terminals, which connect directly to an IP network. The T.38 terminal module
42 extends this module to provide a complete T.38 terminal.
43 - FAX gateways, which allow traditional PSTN FAX terminals to communicate through the Internet.
44 The T.38 gateway module extends this module to provide a T.38 gateway.
45 - A combination of terminals and gateways.
46
47 T.38 is the only standardised protocol which exists for real-time FoIP. Reliably transporting a
48 FAX between PSTN FAX terminals, through an IP network, requires use of the T.38 protocol at FAX
49 gateways. VoIP connections are not robust for modem use, including FAX modem use. Most use low
50 bit rate codecs, which cannot convey the modem signals accurately. Even when high bit rate
51 codecs are used, VoIP connections suffer dropouts and timing adjustments, which modems cannot
52 tolerate. In a LAN environment the dropout rate may be very low, but the timing adjustments which
53 occur in VoIP connections still make modem operation unreliable. T.38 FAX gateways deal with the
54 delays, timing jitter, and packet loss experienced in packet networks, and isolate the PSTN FAX
55 terminals from these as far as possible. In addition, by sending FAXes as image data, rather than
56 digitised audio, they reduce the required bandwidth of the IP network.
57
58 \section t38_core_page_sec_1 What does it do?
59
60 \section t38_core_page_sec_2 How does it work?
61
62 Timing differences and jitter between two T.38 entities can be a serious problem, if one of those
63 entities is a PSTN gateway.
64
65 Flow control for non-ECM image data takes advantage of several features of the T.30 specification.
66 First, an unspecified number of 0xFF octets may be sent at the start of transmission. This means we
67 can add endless extra 0xFF bytes at this point, without breaking the T.30 spec. In practice, we
68 cannot add too many, or we will affect the timing tolerance of the T.30 protocol by delaying the
69 response at the end of each image. Secondly, just before an end of line (EOL) marker we can pad
70 with zero bits. Again, the number is limited only by need to avoid upsetting the timing of the
71 step following the non-ECM data.
72 */
73
74 /*! T.38 indicator types */
75 enum t30_indicator_types_e
76 {
77 T38_IND_NO_SIGNAL = 0,
78 T38_IND_CNG,
79 T38_IND_CED,
80 T38_IND_V21_PREAMBLE,
81 T38_IND_V27TER_2400_TRAINING,
82 T38_IND_V27TER_4800_TRAINING,
83 T38_IND_V29_7200_TRAINING,
84 T38_IND_V29_9600_TRAINING,
85 T38_IND_V17_7200_SHORT_TRAINING,
86 T38_IND_V17_7200_LONG_TRAINING,
87 T38_IND_V17_9600_SHORT_TRAINING,
88 T38_IND_V17_9600_LONG_TRAINING,
89 T38_IND_V17_12000_SHORT_TRAINING,
90 T38_IND_V17_12000_LONG_TRAINING,
91 T38_IND_V17_14400_SHORT_TRAINING,
92 T38_IND_V17_14400_LONG_TRAINING,
93 T38_IND_V8_ANSAM,
94 T38_IND_V8_SIGNAL,
95 T38_IND_V34_CNTL_CHANNEL_1200,
96 T38_IND_V34_PRI_CHANNEL,
97 T38_IND_V34_CC_RETRAIN,
98 T38_IND_V33_12000_TRAINING,
99 T38_IND_V33_14400_TRAINING
100 };
101
102 /*! T.38 data types */
103 enum t38_data_types_e
104 {
105 T38_DATA_NONE = -1,
106 T38_DATA_V21 = 0,
107 T38_DATA_V27TER_2400,
108 T38_DATA_V27TER_4800,
109 T38_DATA_V29_7200,
110 T38_DATA_V29_9600,
111 T38_DATA_V17_7200,
112 T38_DATA_V17_9600,
113 T38_DATA_V17_12000,
114 T38_DATA_V17_14400,
115 T38_DATA_V8,
116 T38_DATA_V34_PRI_RATE,
117 T38_DATA_V34_CC_1200,
118 T38_DATA_V34_PRI_CH,
119 T38_DATA_V33_12000,
120 T38_DATA_V33_14400
121 };
122
123 /*! T.38 data field types */
124 enum t38_field_types_e
125 {
126 T38_FIELD_HDLC_DATA = 0,
127 T38_FIELD_HDLC_SIG_END,
128 T38_FIELD_HDLC_FCS_OK,
129 T38_FIELD_HDLC_FCS_BAD,
130 T38_FIELD_HDLC_FCS_OK_SIG_END,
131 T38_FIELD_HDLC_FCS_BAD_SIG_END,
132 T38_FIELD_T4_NON_ECM_DATA,
133 T38_FIELD_T4_NON_ECM_SIG_END,
134 T38_FIELD_CM_MESSAGE,
135 T38_FIELD_JM_MESSAGE,
136 T38_FIELD_CI_MESSAGE,
137 T38_FIELD_V34RATE
138 };
139
140 /*! T.38 field classes */
141 enum t38_field_classes_e
142 {
143 T38_FIELD_CLASS_NONE = 0,
144 T38_FIELD_CLASS_HDLC,
145 T38_FIELD_CLASS_NON_ECM
146 };
147
148 /*! T.38 message types */
149 enum t38_message_types_e
150 {
151 T38_TYPE_OF_MSG_T30_INDICATOR = 0,
152 T38_TYPE_OF_MSG_T30_DATA
153 };
154
155 /*! T.38 transport types */
156 enum t38_transport_types_e
157 {
158 T38_TRANSPORT_UDPTL = 0,
159 T38_TRANSPORT_RTP,
160 T38_TRANSPORT_TCP
161 };
162
163 /*! T.38 TCF management types */
164 enum t38_data_rate_management_types_e
165 {
166 T38_DATA_RATE_MANAGEMENT_LOCAL_TCF = 1,
167 T38_DATA_RATE_MANAGEMENT_TRANSFERRED_TCF = 2
168 };
169
170 /*! T.38 Packet categories used for setting the redundancy level and packet repeat
171 counts on a packet by packet basis. */
172 enum t38_packet_categories_e
173 {
174 /*! \brief Indicator packet */
175 T38_PACKET_CATEGORY_INDICATOR = 0,
176 /*! \brief Control data packet */
177 T38_PACKET_CATEGORY_CONTROL_DATA = 1,
178 /*! \brief Terminating control data packet */
179 T38_PACKET_CATEGORY_CONTROL_DATA_END = 2,
180 /*! \brief Image data packet */
181 T38_PACKET_CATEGORY_IMAGE_DATA = 3,
182 /*! \brief Terminating image data packet */
183 T38_PACKET_CATEGORY_IMAGE_DATA_END = 4
184 };
185
186 #define T38_RX_BUF_LEN 2048
187 #define T38_TX_BUF_LEN 16384
188
189 /*! T.38 data field */
190 typedef struct
191 {
192 /*! Field type */
193 int field_type;
194 /*! Field contents */
195 const uint8_t *field;
196 /*! Field length */
197 int field_len;
198 } t38_data_field_t;
199
200 /*!
201 Core T.38 state, common to all modes of T.38.
202 */
203 typedef struct t38_core_state_s t38_core_state_t;
204
205 typedef int (t38_tx_packet_handler_t)(t38_core_state_t *s, void *user_data, const uint8_t *buf, int len, int count);
206
207 typedef int (t38_rx_indicator_handler_t)(t38_core_state_t *s, void *user_data, int indicator);
208 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);
209 typedef int (t38_rx_missing_handler_t)(t38_core_state_t *s, void *user_data, int rx_seq_no, int expected_seq_no);
210
211 #if defined(__cplusplus)
212 extern "C"
213 {
214 #endif
215
216 /*! \brief Convert the code for an indicator to a short text name.
217 \param indicator The type of indicator.
218 \return A pointer to a short text name for the indicator. */
219 SPAN_DECLARE(const char *) t38_indicator_to_str(int indicator);
220
221 /*! \brief Convert the code for a type of data to a short text name.
222 \param data_type The data type.
223 \return A pointer to a short text name for the data type. */
224 SPAN_DECLARE(const char *) t38_data_type_to_str(int data_type);
225
226 /*! \brief Convert the code for a type of data field to a short text name.
227 \param field_type The field type.
228 \return A pointer to a short text name for the field type. */
229 SPAN_DECLARE(const char *) t38_field_type_to_str(int field_type);
230
231 /*! \brief Convert the code for a CM profile code to text description.
232 \param profile The profile code from a CM message.
233 \return A pointer to a short text description of the profile. */
234 SPAN_DECLARE(const char *) t38_cm_profile_to_str(int profile);
235
236 /*! \brief Convert a JM message code to text description.
237 \param data The data field of the message.
238 \param len The length of the data field.
239 \return A pointer to a short text description of the profile. */
240 SPAN_DECLARE(const char *) t38_jm_to_str(const uint8_t *data, int len);
241
242 /*! \brief Convert a V34rate message to an actual bit rate.
243 \param data The data field of the message.
244 \param len The length of the data field.
245 \return The bit rate, or -1 for a bad message. */
246 SPAN_DECLARE(int) t38_v34rate_to_bps(const uint8_t *data, int len);
247
248 /*! \brief Send an indicator packet
249 \param s The T.38 context.
250 \param indicator The indicator to send.
251 \return The delay to allow after this indicator is sent. */
252 SPAN_DECLARE(int) t38_core_send_indicator(t38_core_state_t *s, int indicator);
253
254 /*! \brief Find the delay to allow for HDLC flags after sending an indicator
255 \param s The T.38 context.
256 \param indicator The indicator to send.
257 \return The delay to allow for initial HDLC flags after this indicator is sent. */
258 SPAN_DECLARE(int) t38_core_send_flags_delay(t38_core_state_t *s, int indicator);
259
260 /*! \brief Send a data packet
261 \param s The T.38 context.
262 \param data_type The packet's data type.
263 \param field_type The packet's field type.
264 \param field The message data content for the packet.
265 \param field_len The length of the message data, in bytes.
266 \param category The category of the packet being sent. This should be one of the values defined for t38_packet_categories_e.
267 \return ??? */
268 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);
269
270 /*! \brief Send a data packet
271 \param s The T.38 context.
272 \param data_type The packet's data type.
273 \param field The list of fields.
274 \param fields The number of fields in the list.
275 \param category The category of the packet being sent. This should be one of the values defined for t38_packet_categories_e.
276 \return ??? */
277 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);
278
279 /*! \brief Process a received T.38 IFP packet.
280 \param s The T.38 context.
281 \param buf The packet contents.
282 \param len The length of the packet contents.
283 \param seq_no The packet sequence number.
284 \return 0 for OK, else -1. */
285 SPAN_DECLARE(int) t38_core_rx_ifp_packet(t38_core_state_t *s, const uint8_t *buf, int len, uint16_t seq_no);
286
287 /*! Set the method to be used for data rate management, as per the T.38 spec.
288 \param s The T.38 context.
289 \param method 1 for pass TCF across the T.38 link, 2 for handle TCF locally.
290 */
291 SPAN_DECLARE(void) t38_set_data_rate_management_method(t38_core_state_t *s, int method);
292
293 /*! Set the data transport protocol.
294 \param s The T.38 context.
295 \param data_transport_protocol UDPTL, RTP or TPKT.
296 */
297 SPAN_DECLARE(void) t38_set_data_transport_protocol(t38_core_state_t *s, int data_transport_protocol);
298
299 /*! Set the non-ECM fill bit removal mode.
300 \param s The T.38 context.
301 \param fill_bit_removal TRUE to remove fill bits across the T.38 link, else FALSE.
302 */
303 SPAN_DECLARE(void) t38_set_fill_bit_removal(t38_core_state_t *s, int fill_bit_removal);
304
305 /*! Set the MMR transcoding mode.
306 \param s The T.38 context.
307 \param mmr_transcoding TRUE to transcode to MMR across the T.38 link, else FALSE.
308 */
309 SPAN_DECLARE(void) t38_set_mmr_transcoding(t38_core_state_t *s, int mmr_transcoding);
310
311 /*! Set the JBIG transcoding mode.
312 \param s The T.38 context.
313 \param jbig_transcoding TRUE to transcode to JBIG across the T.38 link, else FALSE.
314 */
315 SPAN_DECLARE(void) t38_set_jbig_transcoding(t38_core_state_t *s, int jbig_transcoding);
316
317 /*! Set the maximum buffer size for received data at the far end.
318 \param s The T.38 context.
319 \param max_buffer_size The maximum buffer size.
320 */
321 SPAN_DECLARE(void) t38_set_max_buffer_size(t38_core_state_t *s, int max_buffer_size);
322
323 /*! Set the maximum size of an IFP packet that is acceptable by the far end.
324 \param s The T.38 context.
325 \param max_datagram_size The maximum IFP packet length, in bytes.
326 */
327 SPAN_DECLARE(void) t38_set_max_datagram_size(t38_core_state_t *s, int max_datagram_size);
328
329 /*! \brief Send a data packet
330 \param s The T.38 context.
331 \param category The category of the packet being sent. This should be one of the values defined for t38_packet_categories_e.
332 \param setting The repeat count for the category. This should be at least one for all categories other an indicator packets.
333 Zero is valid for indicator packets, as it suppresses the sending of indicator packets, as an application using
334 TCP for the transport would require. As the setting is passed through to the transmission channel, additional
335 information may be encoded in it, such as the redundancy depth for the particular packet category. */
336 SPAN_DECLARE(void) t38_set_redundancy_control(t38_core_state_t *s, int category, int setting);
337
338 SPAN_DECLARE(void) t38_set_fastest_image_data_rate(t38_core_state_t *s, int max_rate);
339
340 SPAN_DECLARE(int) t38_get_fastest_image_data_rate(t38_core_state_t *s);
341
342 /*! Set the T.38 version to be emulated.
343 \param s The T.38 context.
344 \param t38_version Version number, as in the T.38 spec.
345 */
346 SPAN_DECLARE(void) t38_set_t38_version(t38_core_state_t *s, int t38_version);
347
348 /*! Set the sequence number handling option.
349 \param s The T.38 context.
350 \param check TRUE to check sequence numbers, and handle gaps reasonably. FALSE
351 for no sequence number processing (e.g. for TPKT over TCP transport).
352 */
353 SPAN_DECLARE(void) t38_set_sequence_number_handling(t38_core_state_t *s, int check);
354
355 /*! Set the TEP handling option.
356 \param s The T.38 context.
357 \param allow_for_tep TRUE to allow for TEP playout, else FALSE.
358 */
359 SPAN_DECLARE(void) t38_set_tep_handling(t38_core_state_t *s, int allow_for_tep);
360
361 /*! Get a pointer to the logging context associated with a T.38 context.
362 \brief Get a pointer to the logging context associated with a T.38 context.
363 \param s The T.38 context.
364 \return A pointer to the logging context, or NULL.
365 */
366 SPAN_DECLARE(logging_state_t *) t38_core_get_logging_state(t38_core_state_t *s);
367
368 /*! Initialise a T.38 core context.
369 \brief Initialise a T.38 core context.
370 \param s The T.38 context.
371 \param rx_indicator_handler Receive indicator handling routine.
372 \param rx_data_handler Receive data packet handling routine.
373 \param rx_rx_missing_handler Missing receive packet handling routine.
374 \param rx_packet_user_data An opaque pointer passed to the rx packet handling routines.
375 \param tx_packet_handler Packet transmit handling routine.
376 \param tx_packet_user_data An opaque pointer passed to the tx_packet_handler.
377 \return A pointer to the T.38 context, or NULL if there was a problem. */
378 SPAN_DECLARE(t38_core_state_t *) t38_core_init(t38_core_state_t *s,
379 t38_rx_indicator_handler_t *rx_indicator_handler,
380 t38_rx_data_handler_t *rx_data_handler,
381 t38_rx_missing_handler_t *rx_missing_handler,
382 void *rx_user_data,
383 t38_tx_packet_handler_t *tx_packet_handler,
384 void *tx_packet_user_data);
385
386 /*! Release a signaling tone transmitter context.
387 \brief Release a signaling tone transmitter context.
388 \param s The T.38 context.
389 \return 0 for OK */
390 SPAN_DECLARE(int) t38_core_release(t38_core_state_t *s);
391
392 /*! Free a signaling tone transmitter context.
393 \brief Free a signaling tone transmitter context.
394 \param s The T.38 context.
395 \return 0 for OK */
396 SPAN_DECLARE(int) t38_core_free(t38_core_state_t *s);
397
398 #if defined(__cplusplus)
399 }
400 #endif
401
402 #endif
403 /*- End of file ------------------------------------------------------------*/

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