163 lines
6.9 KiB
C
163 lines
6.9 KiB
C
/*
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* SpanDSP - a series of DSP components for telephony
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*
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* v27ter_rx.h - ITU V.27ter modem receive part
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*
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* Written by Steve Underwood <steveu@coppice.org>
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*
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* Copyright (C) 2003 Steve Underwood
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*
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* All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License version 2.1,
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/*! \file */
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#if !defined(_SPANDSP_V27TER_RX_H_)
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#define _SPANDSP_V27TER_RX_H_
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/*! \page v27ter_rx_page The V.27ter receiver
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\section v27ter_rx_page_sec_1 What does it do?
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The V.27ter receiver implements the receive side of a V.27ter modem. This can operate
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at data rates of 4800 and 2400 bits/s. The audio input is a stream of 16 bit samples,
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at 8000 samples/second. The transmit and receive side of V.27ter modems operate
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independantly. V.27ter is mostly used for FAX transmission, where it provides the
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standard 4800 bits/s rate (the 2400 bits/s mode is not used for FAX).
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\section v27ter_rx_page_sec_2 How does it work?
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V.27ter defines two modes of operation. One uses 8-PSK at 1600 baud, giving 4800bps.
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The other uses 4-PSK at 1200 baud, giving 2400bps. A training sequence is specified
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at the start of transmission, which makes the design of a V.27ter receiver relatively
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straightforward.
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*/
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/*!
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V.27ter modem receive side descriptor. This defines the working state for a
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single instance of a V.27ter modem receiver.
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*/
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typedef struct v27ter_rx_state_s v27ter_rx_state_t;
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#if defined(__cplusplus)
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extern "C"
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{
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#endif
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/*! Initialise a V.27ter modem receive context.
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\brief Initialise a V.27ter modem receive context.
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\param s The modem context.
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\param bit_rate The bit rate of the modem. Valid values are 2400 and 4800.
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\param put_bit The callback routine used to put the received data.
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\param user_data An opaque pointer passed to the put_bit routine.
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\return A pointer to the modem context, or NULL if there was a problem. */
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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);
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/*! Reinitialise an existing V.27ter modem receive context.
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\brief Reinitialise an existing V.27ter modem receive context.
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\param s The modem context.
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\param bit_rate The bit rate of the modem. Valid values are 2400 and 4800.
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\param old_train TRUE if a previous trained values are to be reused.
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\return 0 for OK, -1 for bad parameter */
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SPAN_DECLARE(int) v27ter_rx_restart(v27ter_rx_state_t *s, int bit_rate, int old_train);
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/*! Release a V.27ter modem receive context.
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\brief Release a V.27ter modem receive context.
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\param s The modem context.
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\return 0 for OK */
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SPAN_DECLARE(int) v27ter_rx_release(v27ter_rx_state_t *s);
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/*! Free a V.27ter modem receive context.
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\brief Free a V.27ter modem receive context.
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\param s The modem context.
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\return 0 for OK */
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SPAN_DECLARE(int) v27ter_rx_free(v27ter_rx_state_t *s);
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/*! Get the logging context associated with a V.27ter modem receive context.
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\brief Get the logging context associated with a V.27ter modem receive context.
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\param s The modem context.
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\return A pointer to the logging context */
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SPAN_DECLARE(logging_state_t *) v27ter_rx_get_logging_state(v27ter_rx_state_t *s);
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/*! Change the put_bit function associated with a V.27ter modem receive context.
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\brief Change the put_bit function associated with a V.27ter modem receive context.
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\param s The modem context.
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\param put_bit The callback routine used to handle received bits.
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\param user_data An opaque pointer. */
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SPAN_DECLARE(void) v27ter_rx_set_put_bit(v27ter_rx_state_t *s, put_bit_func_t put_bit, void *user_data);
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/*! Change the modem status report function associated with a V.27ter modem receive context.
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\brief Change the modem status report function associated with a V.27ter modem receive context.
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\param s The modem context.
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\param handler The callback routine used to report modem status changes.
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\param user_data An opaque pointer. */
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SPAN_DECLARE(void) v27ter_rx_set_modem_status_handler(v27ter_rx_state_t *s, modem_rx_status_func_t handler, void *user_data);
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/*! Process a block of received V.27ter modem audio samples.
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\brief Process a block of received V.27ter modem audio samples.
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\param s The modem context.
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\param amp The audio sample buffer.
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\param len The number of samples in the buffer.
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\return The number of samples unprocessed.
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*/
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SPAN_DECLARE_NONSTD(int) v27ter_rx(v27ter_rx_state_t *s, const int16_t amp[], int len);
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/*! Fake processing of a missing block of received V.27ter modem audio samples.
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(e.g due to packet loss).
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\brief Fake processing of a missing block of received V.27ter modem audio samples.
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\param s The modem context.
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\param len The number of samples to fake.
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\return The number of samples unprocessed.
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*/
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SPAN_DECLARE_NONSTD(int) v27ter_rx_fillin(v27ter_rx_state_t *s, int len);
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/*! Get a snapshot of the current equalizer coefficients.
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\brief Get a snapshot of the current equalizer coefficients.
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\param coeffs The vector of complex coefficients.
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\return The number of coefficients in the vector. */
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SPAN_DECLARE(int) v27ter_rx_equalizer_state(v27ter_rx_state_t *s, complexf_t **coeffs);
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/*! Get the current received carrier frequency.
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\param s The modem context.
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\return The frequency, in Hertz. */
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SPAN_DECLARE(float) v27ter_rx_carrier_frequency(v27ter_rx_state_t *s);
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/*! Get the current symbol timing correction since startup.
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\param s The modem context.
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\return The correction. */
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SPAN_DECLARE(float) v27ter_rx_symbol_timing_correction(v27ter_rx_state_t *s);
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/*! Get a current received signal power.
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\param s The modem context.
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\return The signal power, in dBm0. */
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SPAN_DECLARE(float) v27ter_rx_signal_power(v27ter_rx_state_t *s);
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/*! Set the power level at which the carrier detection will cut in
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\param s The modem context.
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\param cutoff The signal cutoff power, in dBm0. */
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SPAN_DECLARE(void) v27ter_rx_signal_cutoff(v27ter_rx_state_t *s, float cutoff);
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/*! Set a handler routine to process QAM status reports
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\param s The modem context.
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\param handler The handler routine.
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\param user_data An opaque pointer passed to the handler routine. */
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SPAN_DECLARE(void) v27ter_rx_set_qam_report_handler(v27ter_rx_state_t *s, qam_report_handler_t handler, void *user_data);
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#if defined(__cplusplus)
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}
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#endif
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#endif
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/*- End of file ------------------------------------------------------------*/
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