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comparison spandsp-0.0.6pre17/src/spandsp/t38_gateway.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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3:c6c5a16ce2f2 4:26cd8f1ef0b1
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 * $Id: t38_gateway.h,v 1.63 2009/04/12 09:12:10 steveu Exp $
26 */
27
28 /*! \file */
29
30 #if !defined(_SPANDSP_T38_GATEWAY_H_)
31 #define _SPANDSP_T38_GATEWAY_H_
32
33 /*! \page t38_gateway_page T.38 real time FAX over IP PSTN gateway
34 \section t38_gateway_page_sec_1 What does it do?
35
36 The T.38 gateway facility provides a robust interface between T.38 IP packet streams and
37 and 8k samples/second audio streams. It provides the buffering and flow control features needed
38 to maximum the tolerance of jitter and packet loss on the IP network.
39
40 \section t38_gateway_page_sec_2 How does it work?
41 */
42
43 /*! The receive buffer length */
44 #define T38_RX_BUF_LEN 2048
45 /*! The number of HDLC transmit buffers */
46 #define T38_TX_HDLC_BUFS 256
47 /*! The maximum length of an HDLC frame buffer. This must be big enough for ECM frames. */
48 #define T38_MAX_HDLC_LEN 260
49
50 typedef struct t38_gateway_state_s t38_gateway_state_t;
51
52 /*!
53 T.30 real time frame handler.
54 \brief T.30 real time frame handler.
55 \param s The T.30 context.
56 \param user_data An opaque pointer.
57 \param direction TRUE for incoming, FALSE for outgoing.
58 \param msg The HDLC message.
59 \param len The length of the message.
60 */
61 typedef void (t38_gateway_real_time_frame_handler_t)(t38_gateway_state_t *s,
62 void *user_data,
63 int direction,
64 const uint8_t *msg,
65 int len);
66
67 /*!
68 T.38 gateway results.
69 */
70 typedef struct
71 {
72 /*! \brief The current bit rate for image transfer. */
73 int bit_rate;
74 /*! \brief TRUE if error correcting mode is used. */
75 int error_correcting_mode;
76 /*! \brief The number of pages transferred so far. */
77 int pages_transferred;
78 } t38_stats_t;
79
80 #if defined(__cplusplus)
81 extern "C"
82 {
83 #endif
84
85 /*! \brief Initialise a gateway mode T.38 context.
86 \param s The T.38 context.
87 \param tx_packet_handler A callback routine to encapsulate and transmit T.38 packets.
88 \param tx_packet_user_data An opaque pointer passed to the tx_packet_handler routine.
89 \return A pointer to the termination mode T.38 context, or NULL if there was a problem. */
90 SPAN_DECLARE(t38_gateway_state_t *) t38_gateway_init(t38_gateway_state_t *s,
91 t38_tx_packet_handler_t *tx_packet_handler,
92 void *tx_packet_user_data);
93
94 /*! Release a gateway mode T.38 context.
95 \brief Release a T.38 context.
96 \param s The T.38 context.
97 \return 0 for OK, else -1. */
98 SPAN_DECLARE(int) t38_gateway_release(t38_gateway_state_t *s);
99
100 /*! Free a gateway mode T.38 context.
101 \brief Free a T.38 context.
102 \param s The T.38 context.
103 \return 0 for OK, else -1. */
104 SPAN_DECLARE(int) t38_gateway_free(t38_gateway_state_t *s);
105
106 /*! Process a block of received FAX audio samples.
107 \brief Process a block of received FAX audio samples.
108 \param s The T.38 context.
109 \param amp The audio sample buffer.
110 \param len The number of samples in the buffer.
111 \return The number of samples unprocessed. */
112 SPAN_DECLARE(int) t38_gateway_rx(t38_gateway_state_t *s, int16_t amp[], int len);
113
114 /*! Generate a block of FAX audio samples.
115 \brief Generate a block of FAX audio samples.
116 \param s The T.38 context.
117 \param amp The audio sample buffer.
118 \param max_len The number of samples to be generated.
119 \return The number of samples actually generated.
120 */
121 SPAN_DECLARE(int) t38_gateway_tx(t38_gateway_state_t *s, int16_t amp[], int max_len);
122
123 /*! Control whether error correcting mode (ECM) is allowed.
124 \brief Control whether error correcting mode (ECM) is allowed.
125 \param s The T.38 context.
126 \param ecm_allowed TRUE is ECM is to be allowed.
127 */
128 SPAN_DECLARE(void) t38_gateway_set_ecm_capability(t38_gateway_state_t *s, int ecm_allowed);
129
130 /*! Select whether silent audio will be sent when transmit is idle.
131 \brief Select whether silent audio will be sent when transmit is idle.
132 \param s The T.38 context.
133 \param transmit_on_idle TRUE if silent audio should be output when the FAX transmitter is
134 idle. FALSE to transmit zero length audio when the FAX transmitter is idle. The default
135 behaviour is FALSE.
136 */
137 SPAN_DECLARE(void) t38_gateway_set_transmit_on_idle(t38_gateway_state_t *s, int transmit_on_idle);
138
139 /*! Specify which modem types are supported by a T.30 context.
140 \brief Specify supported modems.
141 \param s The T.38 context.
142 \param supported_modems Bit field list of the supported modems.
143 */
144 SPAN_DECLARE(void) t38_gateway_set_supported_modems(t38_gateway_state_t *s, int supported_modems);
145
146 /*! Select whether NSC, NSF, and NSS should be suppressed. It selected, the contents of
147 these messages are forced to zero for all octets beyond the message type. This makes
148 them look like manufacturer specific messages, from a manufacturer which does not exist.
149 \brief Select whether NSC, NSF, and NSS should be suppressed.
150 \param s The T.38 context.
151 \param from_t38 A string of bytes to overwrite the header of any NSC, NSF, and NSS
152 frames passing through the gateway from T.38 the the modem.
153 \param from_t38_len The length of the overwrite string.
154 \param from_modem A string of bytes to overwrite the header of any NSC, NSF, and NSS
155 frames passing through the gateway from the modem to T.38.
156 \param from_modem_len The length of the overwrite string.
157 */
158 SPAN_DECLARE(void) t38_gateway_set_nsx_suppression(t38_gateway_state_t *s,
159 const uint8_t *from_t38,
160 int from_t38_len,
161 const uint8_t *from_modem,
162 int from_modem_len);
163
164 /*! Select whether talker echo protection tone will be sent for the image modems.
165 \brief Select whether TEP will be sent for the image modems.
166 \param s The T.38 context.
167 \param use_tep TRUE if TEP should be sent.
168 */
169 SPAN_DECLARE(void) t38_gateway_set_tep_mode(t38_gateway_state_t *s, int use_tep);
170
171 /*! Select whether non-ECM fill bits are to be removed during transmission.
172 \brief Select whether non-ECM fill bits are to be removed during transmission.
173 \param s The T.38 context.
174 \param remove TRUE if fill bits are to be removed.
175 */
176 SPAN_DECLARE(void) t38_gateway_set_fill_bit_removal(t38_gateway_state_t *s, int remove);
177
178 /*! Get the current transfer statistics for the current T.38 session.
179 \brief Get the current transfer statistics.
180 \param s The T.38 context.
181 \param t A pointer to a buffer for the statistics. */
182 SPAN_DECLARE(void) t38_gateway_get_transfer_statistics(t38_gateway_state_t *s, t38_stats_t *t);
183
184 /*! Get a pointer to the T.38 core IFP packet engine associated with a
185 gateway mode T.38 context.
186 \brief Get a pointer to the T.38 core IFP packet engine associated
187 with a T.38 context.
188 \param s The T.38 context.
189 \return A pointer to the T.38 core context, or NULL.
190 */
191 SPAN_DECLARE(t38_core_state_t *) t38_gateway_get_t38_core_state(t38_gateway_state_t *s);
192
193 /*! Get a pointer to the logging context associated with a T.38 context.
194 \brief Get a pointer to the logging context associated with a T.38 context.
195 \param s The T.38 context.
196 \return A pointer to the logging context, or NULL.
197 */
198 SPAN_DECLARE(logging_state_t *) t38_gateway_get_logging_state(t38_gateway_state_t *s);
199
200 /*! Set a callback function for T.30 frame exchange monitoring. This is called from the heart
201 of the signal processing, so don't take too long in the handler routine.
202 \brief Set a callback function for T.30 frame exchange monitoring.
203 \param s The T.30 context.
204 \param handler The callback function.
205 \param user_data An opaque pointer passed to the callback function. */
206 SPAN_DECLARE(void) t38_gateway_set_real_time_frame_handler(t38_gateway_state_t *s,
207 t38_gateway_real_time_frame_handler_t *handler,
208 void *user_data);
209
210 #if defined(__cplusplus)
211 }
212 #endif
213
214 #endif
215 /*- End of file ------------------------------------------------------------*/

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