v27ter_rx.h

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00001 /*
00002  * SpanDSP - a series of DSP components for telephony
00003  *
00004  * v27ter_rx.h - ITU V.27ter modem receive part
00005  *
00006  * Written by Steve Underwood <steveu@coppice.org>
00007  *
00008  * Copyright (C) 2003 Steve Underwood
00009  *
00010  * All rights reserved.
00011  *
00012  * This program is free software; you can redistribute it and/or modify
00013  * it under the terms of the GNU Lesser General Public License version 2.1,
00014  * as published by the Free Software Foundation.
00015  *
00016  * This program is distributed in the hope that it will be useful,
00017  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00018  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00019  * GNU Lesser General Public License for more details.
00020  *
00021  * You should have received a copy of the GNU Lesser General Public
00022  * License along with this program; if not, write to the Free Software
00023  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
00024  */
00025 
00026 /*! \file */
00027 
00028 #if !defined(_SPANDSP_V27TER_RX_H_)
00029 #define _SPANDSP_V27TER_RX_H_
00030 
00031 /*! \page v27ter_rx_page The V.27ter receiver
00032 
00033 \section v27ter_rx_page_sec_1 What does it do?
00034 The V.27ter receiver implements the receive side of a V.27ter modem. This can operate
00035 at data rates of 4800 and 2400 bits/s. The audio input is a stream of 16 bit samples,
00036 at 8000 samples/second. The transmit and receive side of V.27ter modems operate
00037 independantly. V.27ter is mostly used for FAX transmission, where it provides the
00038 standard 4800 bits/s rate (the 2400 bits/s mode is not used for FAX). 
00039 
00040 \section v27ter_rx_page_sec_2 How does it work?
00041 V.27ter defines two modes of operation. One uses 8-PSK at 1600 baud, giving 4800bps.
00042 The other uses 4-PSK at 1200 baud, giving 2400bps. A training sequence is specified
00043 at the start of transmission, which makes the design of a V.27ter receiver relatively
00044 straightforward.
00045 */
00046 
00047 /*!
00048     V.27ter modem receive side descriptor. This defines the working state for a
00049     single instance of a V.27ter modem receiver.
00050 */
00051 typedef struct v27ter_rx_state_s v27ter_rx_state_t;
00052 
00053 #if defined(__cplusplus)
00054 extern "C"
00055 {
00056 #endif
00057 
00058 /*! Initialise a V.27ter modem receive context.
00059     \brief Initialise a V.27ter modem receive context.
00060     \param s The modem context.
00061     \param bit_rate The bit rate of the modem. Valid values are 2400 and 4800.
00062     \param put_bit The callback routine used to put the received data.
00063     \param user_data An opaque pointer passed to the put_bit routine.
00064     \return A pointer to the modem context, or NULL if there was a problem. */
00065 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);
00066 
00067 /*! Reinitialise an existing V.27ter modem receive context.
00068     \brief Reinitialise an existing V.27ter modem receive context.
00069     \param s The modem context.
00070     \param bit_rate The bit rate of the modem. Valid values are 2400 and 4800.
00071     \param old_train TRUE if a previous trained values are to be reused.
00072     \return 0 for OK, -1 for bad parameter */
00073 SPAN_DECLARE(int) v27ter_rx_restart(v27ter_rx_state_t *s, int bit_rate, int old_train);
00074 
00075 /*! Release a V.27ter modem receive context.
00076     \brief Release a V.27ter modem receive context.
00077     \param s The modem context.
00078     \return 0 for OK */
00079 SPAN_DECLARE(int) v27ter_rx_release(v27ter_rx_state_t *s);
00080 
00081 /*! Free a V.27ter modem receive context.
00082     \brief Free a V.27ter modem receive context.
00083     \param s The modem context.
00084     \return 0 for OK */
00085 SPAN_DECLARE(int) v27ter_rx_free(v27ter_rx_state_t *s);
00086 
00087 /*! Get the logging context associated with a V.27ter modem receive context.
00088     \brief Get the logging context associated with a V.27ter modem receive context.
00089     \param s The modem context.
00090     \return A pointer to the logging context */
00091 SPAN_DECLARE(logging_state_t *) v27ter_rx_get_logging_state(v27ter_rx_state_t *s);
00092 
00093 /*! Change the put_bit function associated with a V.27ter modem receive context.
00094     \brief Change the put_bit function associated with a V.27ter modem receive context.
00095     \param s The modem context.
00096     \param put_bit The callback routine used to handle received bits.
00097     \param user_data An opaque pointer. */
00098 SPAN_DECLARE(void) v27ter_rx_set_put_bit(v27ter_rx_state_t *s, put_bit_func_t put_bit, void *user_data);
00099 
00100 /*! Change the modem status report function associated with a V.27ter modem receive context.
00101     \brief Change the modem status report function associated with a V.27ter modem receive context.
00102     \param s The modem context.
00103     \param handler The callback routine used to report modem status changes.
00104     \param user_data An opaque pointer. */
00105 SPAN_DECLARE(void) v27ter_rx_set_modem_status_handler(v27ter_rx_state_t *s, modem_rx_status_func_t handler, void *user_data);
00106 
00107 /*! Process a block of received V.27ter modem audio samples.
00108     \brief Process a block of received V.27ter modem audio samples.
00109     \param s The modem context.
00110     \param amp The audio sample buffer.
00111     \param len The number of samples in the buffer.
00112     \return The number of samples unprocessed.
00113 */
00114 SPAN_DECLARE_NONSTD(int) v27ter_rx(v27ter_rx_state_t *s, const int16_t amp[], int len);
00115 
00116 /*! Fake processing of a missing block of received V.27ter modem audio samples.
00117     (e.g due to packet loss).
00118     \brief Fake processing of a missing block of received V.27ter modem audio samples.
00119     \param s The modem context.
00120     \param len The number of samples to fake.
00121     \return The number of samples unprocessed.
00122 */
00123 SPAN_DECLARE_NONSTD(int) v27ter_rx_fillin(v27ter_rx_state_t *s, int len);
00124 
00125 /*! Get a snapshot of the current equalizer coefficients.
00126     \brief Get a snapshot of the current equalizer coefficients.
00127     \param coeffs The vector of complex coefficients.
00128     \return The number of coefficients in the vector. */
00129 SPAN_DECLARE(int) v27ter_rx_equalizer_state(v27ter_rx_state_t *s, complexf_t **coeffs);
00130 
00131 /*! Get the current received carrier frequency.
00132     \param s The modem context.
00133     \return The frequency, in Hertz. */
00134 SPAN_DECLARE(float) v27ter_rx_carrier_frequency(v27ter_rx_state_t *s);
00135 
00136 /*! Get the current symbol timing correction since startup.
00137     \param s The modem context.
00138     \return The correction. */
00139 SPAN_DECLARE(float) v27ter_rx_symbol_timing_correction(v27ter_rx_state_t *s);
00140 
00141 /*! Get a current received signal power.
00142     \param s The modem context.
00143     \return The signal power, in dBm0. */
00144 SPAN_DECLARE(float) v27ter_rx_signal_power(v27ter_rx_state_t *s);
00145 
00146 /*! Set the power level at which the carrier detection will cut in
00147     \param s The modem context.
00148     \param cutoff The signal cutoff power, in dBm0. */
00149 SPAN_DECLARE(void) v27ter_rx_signal_cutoff(v27ter_rx_state_t *s, float cutoff);
00150 
00151 /*! Set a handler routine to process QAM status reports
00152     \param s The modem context.
00153     \param handler The handler routine.
00154     \param user_data An opaque pointer passed to the handler routine. */
00155 SPAN_DECLARE(void) v27ter_rx_set_qam_report_handler(v27ter_rx_state_t *s, qam_report_handler_t handler, void *user_data);
00156 
00157 #if defined(__cplusplus)
00158 }
00159 #endif
00160 
00161 #endif
00162 /*- End of file ------------------------------------------------------------*/