Mercurial > hg > audiostuff

comparison spandsp-0.0.3/spandsp-0.0.3/src/spandsp/v27ter_rx.h @ 5:f762bf195c4b

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
import spandsp-0.0.3
author Peter Meerwald <pmeerw@cosy.sbg.ac.at>
date Fri, 25 Jun 2010 16:00:21 +0200
parents
children
comparison
equal deleted inserted replaced
4:26cd8f1ef0b1 5:f762bf195c4b
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 General Public License version 2, as
14 * 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 General Public License for more details.
20 *
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 *
25 * $Id: v27ter_rx.h,v 1.34 2006/10/24 13:45:28 steveu Exp $
26 */
27
28 /*! \file */
29
30 #if !defined(_V27TER_RX_H_)
31 #define _V27TER_RX_H_
32
33 /*! \page v27ter_rx_page The V.27ter receiver
34
35 \section v27ter_rx_page_sec_1 What does it do?
36 The V.27ter receiver implements the receive side of a V.27ter modem. This can operate
37 at data rates of 4800 and 2400 bits/s. The audio input is a stream of 16 bit samples,
38 at 8000 samples/second. The transmit and receive side of V.27ter modems operate
39 independantly. V.27ter is mostly used for FAX transmission, where it provides the
40 standard 4800 bits/s rate (the 2400 bits/s mode is not used for FAX).
41
42 \section v27ter_rx_page_sec_2 How does it work?
43 V.27ter defines two modes of operation. One uses 8-PSK at 1600 baud, giving 4800bps.
44 The other uses 4-PSK at 1200 baud, giving 2400bps. A training sequence is specified
45 at the start of transmission, which makes the design of a V.27ter receiver relatively
46 straightforward.
47 */
48
49 /* Target length for the equalizer is about 43 taps for 4800bps and 32 taps for 2400bps
50 to deal with the worst stuff in V.56bis. */
51 #define V27TER_EQUALIZER_PRE_LEN 15 /* this much before the real event */
52 #define V27TER_EQUALIZER_POST_LEN 15 /* this much after the real event */
53 #define V27TER_EQUALIZER_MASK 63 /* one less than a power of 2 >= (V27TER_EQUALIZER_PRE_LEN + 1 + V27TER_EQUALIZER_POST_LEN) */
54
55 #define V27TER_RX_4800_FILTER_STEPS 27
56 #define V27TER_RX_2400_FILTER_STEPS 27
57
58 #if V27TER_RX_4800_FILTER_STEPS > V27TER_RX_2400_FILTER_STEPS
59 #define V27TER_RX_FILTER_STEPS V27TER_RX_4800_FILTER_STEPS
60 #else
61 #define V27TER_RX_FILTER_STEPS V27TER_RX_2400_FILTER_STEPS
62 #endif
63
64 /*!
65 V.27ter modem receive side descriptor. This defines the working state for a
66 single instance of a V.27ter modem receiver.
67 */
68 typedef struct
69 {
70 /*! \brief The bit rate of the modem. Valid values are 2400 and 4800. */
71 int bit_rate;
72 /*! \brief The callback function used to put each bit received. */
73 put_bit_func_t put_bit;
74 /*! \brief A user specified opaque pointer passed to the put_bit routine. */
75 void *user_data;
76 /*! \brief A callback function which may be enabled to report every symbol's
77 constellation position. */
78 qam_report_handler_t *qam_report;
79 /*! \brief A user specified opaque pointer passed to the qam_report callback
80 routine. */
81 void *qam_user_data;
82
83 /*! \brief The route raised cosine (RRC) pulse shaping filter buffer. */
84 float rrc_filter[2*V27TER_RX_FILTER_STEPS];
85 /*! \brief Current offset into the RRC pulse shaping filter buffer. */
86 int rrc_filter_step;
87
88 /*! \brief The register for the training and data scrambler. */
89 unsigned int scramble_reg;
90 /*! \brief A counter for the number of consecutive bits of repeating pattern through
91 the scrambler. */
92 int scrambler_pattern_count;
93 int in_training;
94 int training_bc;
95 int training_count;
96 float training_error;
97 int carrier_present;
98 int16_t last_sample;
99 /*! \brief TRUE if the previous trained values are to be reused. */
100 int old_train;
101
102 /*! \brief The current phase of the carrier (i.e. the DDS parameter). */
103 uint32_t carrier_phase;
104 /*! \brief The update rate for the phase of the carrier (i.e. the DDS increment). */
105 int32_t carrier_phase_rate;
106 /*! \brief The carrier update rate saved for reuse when using short training. */
107 int32_t carrier_phase_rate_save;
108 float carrier_track_p;
109 float carrier_track_i;
110
111 power_meter_t power;
112 int32_t carrier_on_power;
113 int32_t carrier_off_power;
114 float agc_scaling;
115 float agc_scaling_save;
116
117 int constellation_state;
118
119 float eq_delta;
120 /*! \brief The adaptive equalizer coefficients */
121 complexf_t eq_coeff[V27TER_EQUALIZER_PRE_LEN + 1 + V27TER_EQUALIZER_POST_LEN];
122 complexf_t eq_coeff_save[V27TER_EQUALIZER_PRE_LEN + 1 + V27TER_EQUALIZER_POST_LEN];
123 complexf_t eq_buf[V27TER_EQUALIZER_MASK + 1];
124 /*! \brief Current offset into equalizer buffer. */
125 int eq_step;
126 int eq_put_step;
127 int eq_skip;
128
129 /*! \brief Integration variable for damping the Gardner algorithm tests. */
130 int gardner_integrate;
131 /*! \brief Current step size of Gardner algorithm integration. */
132 int gardner_step;
133 /*! \brief The total symbol timing correction since the carrier came up.
134 This is only for performance analysis purposes. */
135 int total_baud_timing_correction;
136 /*! \brief The current fractional phase of the baud timing. */
137 int baud_phase;
138
139 /*! \brief Starting phase angles for the coarse carrier aquisition step. */
140 int32_t start_angles[2];
141 /*! \brief History list of phase angles for the coarse carrier aquisition step. */
142 int32_t angles[16];
143 /*! \brief Error and flow logging control */
144 logging_state_t logging;
145 } v27ter_rx_state_t;
146
147 #ifdef __cplusplus
148 extern "C" {
149 #endif
150
151 /*! Initialise a V.27ter modem receive context.
152 \brief Initialise a V.27ter modem receive context.
153 \param s The modem context.
154 \param rate The bit rate of the modem. Valid values are 2400 and 4800.
155 \param put_bit The callback routine used to put the received data.
156 \param user_data An opaque pointer passed to the put_bit routine.
157 \return A pointer to the modem context, or NULL if there was a problem. */
158 v27ter_rx_state_t *v27ter_rx_init(v27ter_rx_state_t *s, int rate, put_bit_func_t put_bit, void *user_data);
159
160 /*! Reinitialise an existing V.27ter modem receive context.
161 \brief Reinitialise an existing V.27ter modem receive context.
162 \param s The modem context.
163 \param rate The bit rate of the modem. Valid values are 2400 and 4800.
164 \param old_train TRUE if a previous trained values are to be reused.
165 \return 0 for OK, -1 for bad parameter */
166 int v27ter_rx_restart(v27ter_rx_state_t *s, int rate, int old_train);
167
168 /*! Release a V.27ter modem receive context.
169 \brief Release a V.27ter modem receive context.
170 \param s The modem context.
171 \return 0 for OK */
172 int v27ter_rx_release(v27ter_rx_state_t *s);
173
174 /*! Change the put_bit function associated with a V.27ter modem receive context.
175 \brief Change the put_bit function associated with a V.27ter modem receive context.
176 \param s The modem context.
177 \param put_bit The callback routine used to handle received bits.
178 \param user_data An opaque pointer. */
179 void v27ter_rx_set_put_bit(v27ter_rx_state_t *s, put_bit_func_t put_bit, void *user_data);
180
181 /*! Process a block of received V.27ter modem audio samples.
182 \brief Process a block of received V.27ter modem audio samples.
183 \param s The modem context.
184 \param amp The audio sample buffer.
185 \param len The number of samples in the buffer.
186 \return The number of samples unprocessed.
187 */
188 int v27ter_rx(v27ter_rx_state_t *s, const int16_t amp[], int len);
189
190 /*! Get a snapshot of the current equalizer coefficients.
191 \brief Get a snapshot of the current equalizer coefficients.
192 \param coeffs The vector of complex coefficients.
193 \return The number of coefficients in the vector. */
194 int v27ter_rx_equalizer_state(v27ter_rx_state_t *s, complexf_t **coeffs);
195
196 /*! Get the current received carrier frequency.
197 \param s The modem context.
198 \return The frequency, in Hertz. */
199 float v27ter_rx_carrier_frequency(v27ter_rx_state_t *s);
200
201 /*! Get the current symbol timing correction since startup.
202 \param s The modem context.
203 \return The correction. */
204 float v27ter_rx_symbol_timing_correction(v27ter_rx_state_t *s);
205
206 /*! Get a current received signal power.
207 \param s The modem context.
208 \return The signal power, in dBm0. */
209 float v27ter_rx_signal_power(v27ter_rx_state_t *s);
210
211 /*! Set the power level at which the carrier detection will cut in
212 \param s The modem context.
213 \param cutoff The signal cutoff power, in dBm0. */
214 void v27ter_rx_signal_cutoff(v27ter_rx_state_t *s, float cutoff);
215
216 /*! Set a handler routine to process QAM status reports
217 \param s The modem context.
218 \param handler The handler routine.
219 \param user_data An opaque pointer passed to the handler routine. */
220 void v27ter_rx_set_qam_report_handler(v27ter_rx_state_t *s, qam_report_handler_t *handler, void *user_data);
221
222 #ifdef __cplusplus
223 }
224 #endif
225
226 #endif
227 /*- End of file ------------------------------------------------------------*/

Repositories maintained by Peter Meerwald, pmeerw@pmeerw.net.