spandsp  0.0.6
private/t31.h
1 /*
2  * SpanDSP - a series of DSP components for telephony
3  *
4  * private/t31.h - A T.31 compatible class 1 FAX modem interface.
5  *
6  * Written by Steve Underwood <steveu@coppice.org>
7  *
8  * Copyright (C) 2004 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 #if !defined(_SPANDSP_PRIVATE_T31_H_)
27 #define _SPANDSP_PRIVATE_T31_H_
28 
29 /*!
30  Analogue FAX front end channel descriptor. This defines the state of a single working
31  instance of an analogue line FAX front end.
32 */
33 typedef struct
34 {
35  fax_modems_state_t modems;
36  //v8_state_t v8;
37 
38  /*! The transmit signal handler to be used when the current one has finished sending. */
39  span_tx_handler_t *next_tx_handler;
40  void *next_tx_user_data;
41 
42  /*! \brief No of data bits in current_byte. */
43  int bit_no;
44  /*! \brief The current data byte in progress. */
46 
47  /*! \brief Rx power meter, used to detect silence. */
49  /*! \brief Last sample, used for an elementary HPF for the power meter. */
50  int16_t last_sample;
51  /*! \brief The current silence threshold. */
53 
54  /*! \brief Samples of silence heard */
57 
58 /*!
59  Analogue FAX front end channel descriptor. This defines the state of a single working
60  instance of an analogue line FAX front end.
61 */
62 typedef struct
63 {
64  /*! \brief Internet Aware FAX mode bit mask. */
65  int iaf;
66  /*! \brief Required time between T.38 transmissions, in ms. */
68  /*! \brief Bit fields controlling the way data is packed into chunked for transmission. */
70 
71  /*! \brief Core T.38 IFP support */
73 
74  /*! \brief The current transmit step being timed */
76 
77  /*! \brief TRUE is there has been some T.38 data missed */
79 
80  /*! \brief The number of octets to send in each image packet (non-ECM or ECM) at the current
81  rate and the current specified packet interval. */
83 
84  /*! \brief An HDLC context used when sending HDLC messages to the terminal port
85  (ECM mode support). */
87  /*! \brief An HDLC context used when receiving HDLC messages from the terminal port.
88  (ECM mode support). */
90 
91  struct
92  {
93  uint8_t buf[T31_T38_MAX_HDLC_LEN];
94  int len;
95  } hdlc_rx;
96 
97  struct
98  {
99  /*! \brief The number of extra bits in a fully stuffed version of the
100  contents of the HDLC transmit buffer. This is needed to accurately
101  estimate the playout time for this frame, through an analogue modem. */
103  } hdlc_tx;
104 
105  /*! \brief TRUE if we are using ECM mode. This is used to select HDLC faking, necessary
106  with clunky class 1 modems. */
107  int ecm_mode;
108 
109  /*! \brief Counter for trailing non-ECM bytes, used to flush out the far end's modem. */
111 
112  /*! \brief The next queued tramsit indicator */
114  /*! \brief The current T.38 data type being transmitted */
116 
117  /*! \brief The current operating mode of the receiver. */
119  /*! \brief The current operating mode of the transmitter. */
121 
122  /*! \brief Current transmission bit rate. */
124  /*! \brief A "sample" count, used to time events. */
125  int32_t samples;
126  /*! \brief The value for samples at the next transmission point. */
128  /*! \brief The current receive timeout. */
131 
132 /*!
133  T.31 descriptor. This defines the working state for a single instance of
134  a T.31 FAX modem.
135 */
137 {
138  at_state_t at_state;
139  t31_modem_control_handler_t *modem_control_handler;
140  void *modem_control_user_data;
141 
144  /*! TRUE if working in T.38 mode. */
145  int t38_mode;
146 
147  /*! HDLC buffer, for composing an HDLC frame from the computer to the channel. */
148  struct
149  {
150  uint8_t buf[T31_MAX_HDLC_LEN];
151  int len;
152  int ptr;
153  /*! \brief TRUE when the end of HDLC data from the computer has been detected. */
154  int final;
155  } hdlc_tx;
156  /*! Buffer for data from the computer to the channel. */
157  struct
158  {
159  uint8_t data[T31_TX_BUF_LEN];
160  /*! \brief The number of bytes stored in transmit buffer. */
161  int in_bytes;
162  /*! \brief The number of bytes sent from the transmit buffer. */
164  /*! \brief TRUE if the flow of real data has started. */
166  /*! \brief TRUE if holding up further data into the buffer, for flow control. */
167  int holding;
168  /*! \brief TRUE when the end of non-ECM data from the computer has been detected. */
169  int final;
170  } tx;
171 
172  /*! TRUE if DLE prefix just used */
173  int dled;
174 
175  /*! \brief Samples of silence awaited, as specified in a "wait for silence" command */
177 
178  /*! \brief The current bit rate for the FAX fast message transfer modem. */
179  int bit_rate;
180  /*! \brief TRUE if a valid HDLC frame has been received in the current reception period. */
182 
183  /*! \brief Samples elapsed in the current call */
184  int64_t call_samples;
185  int64_t dte_data_timeout;
186 
187  /*! \brief The currently queued modem type. */
188  int modem;
189  /*! \brief TRUE when short training mode has been selected by the computer. */
191  queue_state_t *rx_queue;
192 
193  /*! \brief Error and flow logging control */
195 };
196 
197 #endif
198 /*- End of file ------------------------------------------------------------*/