Mercurial > hg > audiostuff
diff spandsp-0.0.3/spandsp-0.0.3/src/spandsp/v27ter_rx.h @ 5:f762bf195c4b
import spandsp-0.0.3
author | Peter Meerwald <pmeerw@cosy.sbg.ac.at> |
---|---|
date | Fri, 25 Jun 2010 16:00:21 +0200 |
parents | |
children |
line wrap: on
line diff
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/spandsp-0.0.3/spandsp-0.0.3/src/spandsp/v27ter_rx.h Fri Jun 25 16:00:21 2010 +0200 @@ -0,0 +1,227 @@ +/* + * SpanDSP - a series of DSP components for telephony + * + * v27ter_rx.h - ITU V.27ter modem receive part + * + * Written by Steve Underwood <steveu@coppice.org> + * + * Copyright (C) 2003 Steve Underwood + * + * All rights reserved. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2, as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + * + * $Id: v27ter_rx.h,v 1.34 2006/10/24 13:45:28 steveu Exp $ + */ + +/*! \file */ + +#if !defined(_V27TER_RX_H_) +#define _V27TER_RX_H_ + +/*! \page v27ter_rx_page The V.27ter receiver + +\section v27ter_rx_page_sec_1 What does it do? +The V.27ter receiver implements the receive side of a V.27ter modem. This can operate +at data rates of 4800 and 2400 bits/s. The audio input is a stream of 16 bit samples, +at 8000 samples/second. The transmit and receive side of V.27ter modems operate +independantly. V.27ter is mostly used for FAX transmission, where it provides the +standard 4800 bits/s rate (the 2400 bits/s mode is not used for FAX). + +\section v27ter_rx_page_sec_2 How does it work? +V.27ter defines two modes of operation. One uses 8-PSK at 1600 baud, giving 4800bps. +The other uses 4-PSK at 1200 baud, giving 2400bps. A training sequence is specified +at the start of transmission, which makes the design of a V.27ter receiver relatively +straightforward. +*/ + +/* Target length for the equalizer is about 43 taps for 4800bps and 32 taps for 2400bps + to deal with the worst stuff in V.56bis. */ +#define V27TER_EQUALIZER_PRE_LEN 15 /* this much before the real event */ +#define V27TER_EQUALIZER_POST_LEN 15 /* this much after the real event */ +#define V27TER_EQUALIZER_MASK 63 /* one less than a power of 2 >= (V27TER_EQUALIZER_PRE_LEN + 1 + V27TER_EQUALIZER_POST_LEN) */ + +#define V27TER_RX_4800_FILTER_STEPS 27 +#define V27TER_RX_2400_FILTER_STEPS 27 + +#if V27TER_RX_4800_FILTER_STEPS > V27TER_RX_2400_FILTER_STEPS +#define V27TER_RX_FILTER_STEPS V27TER_RX_4800_FILTER_STEPS +#else +#define V27TER_RX_FILTER_STEPS V27TER_RX_2400_FILTER_STEPS +#endif + +/*! + V.27ter modem receive side descriptor. This defines the working state for a + single instance of a V.27ter modem receiver. +*/ +typedef struct +{ + /*! \brief The bit rate of the modem. Valid values are 2400 and 4800. */ + int bit_rate; + /*! \brief The callback function used to put each bit received. */ + put_bit_func_t put_bit; + /*! \brief A user specified opaque pointer passed to the put_bit routine. */ + void *user_data; + /*! \brief A callback function which may be enabled to report every symbol's + constellation position. */ + qam_report_handler_t *qam_report; + /*! \brief A user specified opaque pointer passed to the qam_report callback + routine. */ + void *qam_user_data; + + /*! \brief The route raised cosine (RRC) pulse shaping filter buffer. */ + float rrc_filter[2*V27TER_RX_FILTER_STEPS]; + /*! \brief Current offset into the RRC pulse shaping filter buffer. */ + int rrc_filter_step; + + /*! \brief The register for the training and data scrambler. */ + unsigned int scramble_reg; + /*! \brief A counter for the number of consecutive bits of repeating pattern through + the scrambler. */ + int scrambler_pattern_count; + int in_training; + int training_bc; + int training_count; + float training_error; + int carrier_present; + int16_t last_sample; + /*! \brief TRUE if the previous trained values are to be reused. */ + int old_train; + + /*! \brief The current phase of the carrier (i.e. the DDS parameter). */ + uint32_t carrier_phase; + /*! \brief The update rate for the phase of the carrier (i.e. the DDS increment). */ + int32_t carrier_phase_rate; + /*! \brief The carrier update rate saved for reuse when using short training. */ + int32_t carrier_phase_rate_save; + float carrier_track_p; + float carrier_track_i; + + power_meter_t power; + int32_t carrier_on_power; + int32_t carrier_off_power; + float agc_scaling; + float agc_scaling_save; + + int constellation_state; + + float eq_delta; + /*! \brief The adaptive equalizer coefficients */ + complexf_t eq_coeff[V27TER_EQUALIZER_PRE_LEN + 1 + V27TER_EQUALIZER_POST_LEN]; + complexf_t eq_coeff_save[V27TER_EQUALIZER_PRE_LEN + 1 + V27TER_EQUALIZER_POST_LEN]; + complexf_t eq_buf[V27TER_EQUALIZER_MASK + 1]; + /*! \brief Current offset into equalizer buffer. */ + int eq_step; + int eq_put_step; + int eq_skip; + + /*! \brief Integration variable for damping the Gardner algorithm tests. */ + int gardner_integrate; + /*! \brief Current step size of Gardner algorithm integration. */ + int gardner_step; + /*! \brief The total symbol timing correction since the carrier came up. + This is only for performance analysis purposes. */ + int total_baud_timing_correction; + /*! \brief The current fractional phase of the baud timing. */ + int baud_phase; + + /*! \brief Starting phase angles for the coarse carrier aquisition step. */ + int32_t start_angles[2]; + /*! \brief History list of phase angles for the coarse carrier aquisition step. */ + int32_t angles[16]; + /*! \brief Error and flow logging control */ + logging_state_t logging; +} v27ter_rx_state_t; + +#ifdef __cplusplus +extern "C" { +#endif + +/*! Initialise a V.27ter modem receive context. + \brief Initialise a V.27ter modem receive context. + \param s The modem context. + \param rate The bit rate of the modem. Valid values are 2400 and 4800. + \param put_bit The callback routine used to put the received data. + \param user_data An opaque pointer passed to the put_bit routine. + \return A pointer to the modem context, or NULL if there was a problem. */ +v27ter_rx_state_t *v27ter_rx_init(v27ter_rx_state_t *s, int rate, put_bit_func_t put_bit, void *user_data); + +/*! Reinitialise an existing V.27ter modem receive context. + \brief Reinitialise an existing V.27ter modem receive context. + \param s The modem context. + \param rate The bit rate of the modem. Valid values are 2400 and 4800. + \param old_train TRUE if a previous trained values are to be reused. + \return 0 for OK, -1 for bad parameter */ +int v27ter_rx_restart(v27ter_rx_state_t *s, int rate, int old_train); + +/*! Release a V.27ter modem receive context. + \brief Release a V.27ter modem receive context. + \param s The modem context. + \return 0 for OK */ +int v27ter_rx_release(v27ter_rx_state_t *s); + +/*! Change the put_bit function associated with a V.27ter modem receive context. + \brief Change the put_bit function associated with a V.27ter modem receive context. + \param s The modem context. + \param put_bit The callback routine used to handle received bits. + \param user_data An opaque pointer. */ +void v27ter_rx_set_put_bit(v27ter_rx_state_t *s, put_bit_func_t put_bit, void *user_data); + +/*! Process a block of received V.27ter modem audio samples. + \brief Process a block of received V.27ter modem audio samples. + \param s The modem context. + \param amp The audio sample buffer. + \param len The number of samples in the buffer. + \return The number of samples unprocessed. +*/ +int v27ter_rx(v27ter_rx_state_t *s, const int16_t amp[], int len); + +/*! Get a snapshot of the current equalizer coefficients. + \brief Get a snapshot of the current equalizer coefficients. + \param coeffs The vector of complex coefficients. + \return The number of coefficients in the vector. */ +int v27ter_rx_equalizer_state(v27ter_rx_state_t *s, complexf_t **coeffs); + +/*! Get the current received carrier frequency. + \param s The modem context. + \return The frequency, in Hertz. */ +float v27ter_rx_carrier_frequency(v27ter_rx_state_t *s); + +/*! Get the current symbol timing correction since startup. + \param s The modem context. + \return The correction. */ +float v27ter_rx_symbol_timing_correction(v27ter_rx_state_t *s); + +/*! Get a current received signal power. + \param s The modem context. + \return The signal power, in dBm0. */ +float v27ter_rx_signal_power(v27ter_rx_state_t *s); + +/*! Set the power level at which the carrier detection will cut in + \param s The modem context. + \param cutoff The signal cutoff power, in dBm0. */ +void v27ter_rx_signal_cutoff(v27ter_rx_state_t *s, float cutoff); + +/*! Set a handler routine to process QAM status reports + \param s The modem context. + \param handler The handler routine. + \param user_data An opaque pointer passed to the handler routine. */ +void v27ter_rx_set_qam_report_handler(v27ter_rx_state_t *s, qam_report_handler_t *handler, void *user_data); + +#ifdef __cplusplus +} +#endif + +#endif +/*- End of file ------------------------------------------------------------*/