spandsp  3.0.0
v27ter_rx.h
Go to the documentation of this file.
1 /*
2  * SpanDSP - a series of DSP components for telephony
3  *
4  * v27ter_rx.h - ITU V.27ter modem receive part
5  *
6  * Written by Steve Underwood <steveu@coppice.org>
7  *
8  * Copyright (C) 2003 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_V27TER_RX_H_)
29 #define _SPANDSP_V27TER_RX_H_
30 
31 /*! \page v27ter_rx_page The V.27ter receiver
32 
33 \section v27ter_rx_page_sec_1 What does it do?
34 The V.27ter receiver implements the receive side of a V.27ter modem. This can operate
35 at data rates of 4800 and 2400 bits/s. The audio input is a stream of 16 bit samples,
36 at 8000 samples/second. The transmit and receive side of V.27ter modems operate
37 independantly. V.27ter is mostly used for FAX transmission, where it provides the
38 standard 4800 bits/s rate (the 2400 bits/s mode is not used for FAX).
39 
40 \section v27ter_rx_page_sec_2 How does it work?
41 V.27ter defines two modes of operation. One uses 8-PSK at 1600 baud, giving 4800bps.
42 The other uses 4-PSK at 1200 baud, giving 2400bps. A training sequence is specified
43 at the start of transmission, which makes the design of a V.27ter receiver relatively
44 straightforward.
45 */
46 
47 #if defined(SPANDSP_USE_FIXED_POINT)
48 #define V27TER_CONSTELLATION_SCALING_FACTOR 1024.0
49 #else
50 #define V27TER_CONSTELLATION_SCALING_FACTOR 1.0
51 #endif
52 
53 /*!
54  V.27ter modem receive side descriptor. This defines the working state for a
55  single instance of a V.27ter modem receiver.
56 */
58 
59 #if defined(__cplusplus)
60 extern "C"
61 {
62 #endif
63 
64 /*! Initialise a V.27ter modem receive context.
65  \brief Initialise a V.27ter modem receive context.
66  \param s The modem context.
67  \param bit_rate The bit rate of the modem. Valid values are 2400 and 4800.
68  \param put_bit The callback routine used to put the received data.
69  \param user_data An opaque pointer passed to the put_bit routine.
70  \return A pointer to the modem context, or NULL if there was a problem. */
71 SPAN_DECLARE(v27ter_rx_state_t *) v27ter_rx_init(v27ter_rx_state_t *s, int bit_rate, put_bit_func_t put_bit, void *user_data);
72 
73 /*! Reinitialise an existing V.27ter modem receive context.
74  \brief Reinitialise an existing V.27ter modem receive context.
75  \param s The modem context.
76  \param bit_rate The bit rate of the modem. Valid values are 2400 and 4800.
77  \param old_train True if a previous trained values are to be reused.
78  \return 0 for OK, -1 for bad parameter */
79 SPAN_DECLARE(int) v27ter_rx_restart(v27ter_rx_state_t *s, int bit_rate, bool old_train);
80 
81 /*! Release a V.27ter modem receive context.
82  \brief Release a V.27ter modem receive context.
83  \param s The modem context.
84  \return 0 for OK */
85 SPAN_DECLARE(int) v27ter_rx_release(v27ter_rx_state_t *s);
86 
87 /*! Free a V.27ter modem receive context.
88  \brief Free a V.27ter modem receive context.
89  \param s The modem context.
90  \return 0 for OK */
91 SPAN_DECLARE(int) v27ter_rx_free(v27ter_rx_state_t *s);
92 
93 /*! Get the logging context associated with a V.27ter modem receive context.
94  \brief Get the logging context associated with a V.27ter modem receive context.
95  \param s The modem context.
96  \return A pointer to the logging context */
98 
99 /*! Change the put_bit function associated with a V.27ter modem receive context.
100  \brief Change the put_bit function associated with a V.27ter modem receive context.
101  \param s The modem context.
102  \param put_bit The callback routine used to handle received bits.
103  \param user_data An opaque pointer. */
104 SPAN_DECLARE(void) v27ter_rx_set_put_bit(v27ter_rx_state_t *s, put_bit_func_t put_bit, void *user_data);
105 
106 /*! Change the modem status report function associated with a V.27ter modem receive context.
107  \brief Change the modem status report function associated with a V.27ter modem receive context.
108  \param s The modem context.
109  \param handler The callback routine used to report modem status changes.
110  \param user_data An opaque pointer. */
111 SPAN_DECLARE(void) v27ter_rx_set_modem_status_handler(v27ter_rx_state_t *s, modem_status_func_t handler, void *user_data);
112 
113 /*! Process a block of received V.27ter modem audio samples.
114  \brief Process a block of received V.27ter modem audio samples.
115  \param s The modem context.
116  \param amp The audio sample buffer.
117  \param len The number of samples in the buffer.
118  \return The number of samples unprocessed.
119 */
120 SPAN_DECLARE(int) v27ter_rx(v27ter_rx_state_t *s, const int16_t amp[], int len);
121 
122 /*! Fake processing of a missing block of received V.27ter modem audio samples.
123  (e.g due to packet loss).
124  \brief Fake processing of a missing block of received V.27ter modem audio samples.
125  \param s The modem context.
126  \param len The number of samples to fake.
127  \return The number of samples unprocessed.
128 */
129 SPAN_DECLARE(int) v27ter_rx_fillin(v27ter_rx_state_t *s, int len);
130 
131 /*! Get a snapshot of the current equalizer coefficients.
132  \brief Get a snapshot of the current equalizer coefficients.
133  \param coeffs The vector of complex coefficients.
134  \return The number of coefficients in the vector. */
135 #if defined(SPANDSP_USE_FIXED_POINT)
136 SPAN_DECLARE(int) v27ter_rx_equalizer_state(v27ter_rx_state_t *s, complexi16_t **coeffs);
137 #else
138 SPAN_DECLARE(int) v27ter_rx_equalizer_state(v27ter_rx_state_t *s, complexf_t **coeffs);
139 #endif
140 
141 /*! Get the current received carrier frequency.
142  \param s The modem context.
143  \return The frequency, in Hertz. */
144 SPAN_DECLARE(float) v27ter_rx_carrier_frequency(v27ter_rx_state_t *s);
145 
146 /*! Get the current symbol timing correction since startup.
147  \param s The modem context.
148  \return The correction. */
150 
151 /*! Get a current received signal power.
152  \param s The modem context.
153  \return The signal power, in dBm0. */
154 SPAN_DECLARE(float) v27ter_rx_signal_power(v27ter_rx_state_t *s);
155 
156 /*! Set the power level at which the carrier detection will cut in
157  \param s The modem context.
158  \param cutoff The signal cutoff power, in dBm0. */
159 SPAN_DECLARE(void) v27ter_rx_signal_cutoff(v27ter_rx_state_t *s, float cutoff);
160 
161 /*! Set a handler routine to process QAM status reports
162  \param s The modem context.
163  \param handler The handler routine.
164  \param user_data An opaque pointer passed to the handler routine. */
165 SPAN_DECLARE(void) v27ter_rx_set_qam_report_handler(v27ter_rx_state_t *s, qam_report_handler_t handler, void *user_data);
166 
167 #if defined(__cplusplus)
168 }
169 #endif
170 
171 #endif
172 /*- End of file ------------------------------------------------------------*/
float v27ter_rx_symbol_timing_correction(v27ter_rx_state_t *s)
Definition: v27ter_rx.c:143
put_bit_func_t put_bit
The callback function used to put each bit received.
Definition: private/v27ter_rx.h:56
Definition: complex.h:88
int v27ter_rx_release(v27ter_rx_state_t *s)
Release a V.27ter modem receive context.
Definition: v27ter_rx.c:1131
int v27ter_rx_equalizer_state(v27ter_rx_state_t *s, complexf_t **coeffs)
Get a snapshot of the current equalizer coefficients.
Definition: v27ter_rx.c:178
int v27ter_rx_fillin(v27ter_rx_state_t *s, int len)
Fake processing of a missing block of received V.27ter modem audio samples.
Definition: v27ter_rx.c:981
int v27ter_rx_restart(v27ter_rx_state_t *s, int bit_rate, bool old_train)
Reinitialise an existing V.27ter modem receive context.
Definition: v27ter_rx.c:1036
void v27ter_rx_set_qam_report_handler(v27ter_rx_state_t *s, qam_report_handler_t handler, void *user_data)
Definition: v27ter_rx.c:1144
void v27ter_rx_signal_cutoff(v27ter_rx_state_t *s, float cutoff)
Definition: v27ter_rx.c:158
v27ter_rx_state_t * v27ter_rx_init(v27ter_rx_state_t *s, int bit_rate, put_bit_func_t put_bit, void *user_data)
Initialise a V.27ter modem receive context.
Definition: v27ter_rx.c:1104
void(* put_bit_func_t)(void *user_data, int bit)
Definition: async.h:107
void(* modem_status_func_t)(void *user_data, int status)
Definition: async.h:113
int bit_rate
The bit rate of the modem. Valid values are 2400 and 4800.
Definition: private/v27ter_rx.h:54
logging_state_t * v27ter_rx_get_logging_state(v27ter_rx_state_t *s)
Get the logging context associated with a V.27ter modem receive context.
Definition: v27ter_rx.c:1030
float v27ter_rx_signal_power(v27ter_rx_state_t *s)
Definition: v27ter_rx.c:152
Definition: complex.h:42
void v27ter_rx_set_put_bit(v27ter_rx_state_t *s, put_bit_func_t put_bit, void *user_data)
Change the put_bit function associated with a V.27ter modem receive context.
Definition: v27ter_rx.c:1016
Definition: private/logging.h:33
bool old_train
True if the previous trained values are to be reused.
Definition: private/v27ter_rx.h:134
Definition: private/v27ter_rx.h:51
float v27ter_rx_carrier_frequency(v27ter_rx_state_t *s)
Definition: v27ter_rx.c:137
int v27ter_rx_free(v27ter_rx_state_t *s)
Free a V.27ter modem receive context.
Definition: v27ter_rx.c:1137
void v27ter_rx_set_modem_status_handler(v27ter_rx_state_t *s, modem_status_func_t handler, void *user_data)
Change the modem status report function associated with a V.27ter modem receive context.
Definition: v27ter_rx.c:1023
int v27ter_rx(v27ter_rx_state_t *s, const int16_t amp[], int len)
Process a block of received V.27ter modem audio samples.
Definition: v27ter_rx.c:831