/* * SpanDSP - a series of DSP components for telephony * * line_model.h - Model a telephone line. * * Written by Steve Underwood <steveu@coppice.org> * * Copyright (C) 2004 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: line_model.h,v 1.1 2007/04/03 12:59:32 steveu Exp $ *//*! \file *//*! \page line_model_page Telephone line model\section line_model_page_sec_1 What does it do?The telephone line modelling module provides simple modelling of one way and twoway telephone lines.The path being modelled is:    -    terminal    -      | < hybrid echo (2-way models)    -      |    -      | < noise and filtering    -      |    -      | < hybrid echo (2-way models)    -     CO    -      |    -      | < A-law distortion + bulk delay    -      |    -     CO    -      | < hybrid echo (2-way models)    -      |    -      | < noise and filtering    -      |    -      | < hybrid echo (2-way models)    -    terminal*/#if !defined(_SPANDSP_LINE_MODEL_H_)#define _SPANDSP_LINE_MODEL_H_#define LINE_FILTER_SIZE 129/*!    One way line model descriptor. This holds the complete state of    a line model with transmission in only one direction.*/typedef struct{    codec_munge_state_t *munge;    /*! The coefficients for the near end analogue section simulation filter */    float *near_filter;    /*! The number of coefficients for the near end analogue section simulation filter */    int near_filter_len;    /*! Last transmitted samples (ring buffer, used by the line filter) */    float near_buf[LINE_FILTER_SIZE];    /*! Pointer of the last transmitted sample in buf */    int near_buf_ptr;    /*! The noise source for local analogue section of the line */    awgn_state_t near_noise;    /*! The bulk delay of the path, in samples */    int bulk_delay;    /*! A pointer to the current write position in the bulk delay store. */    int bulk_delay_ptr;    /*! The data store for simulating the bulk delay */    int16_t bulk_delay_buf[8000];    /*! The coefficients for the far end analogue section simulation filter */    float *far_filter;    /*! The number of coefficients for the far end analogue section simulation filter */    int far_filter_len;    /*! Last transmitted samples (ring buffer, used by the line filter) */    float far_buf[LINE_FILTER_SIZE];    /*! Pointer of the last transmitted sample in buf */    int far_buf_ptr;    /*! The noise source for distant analogue section of the line */    awgn_state_t far_noise;    /*! The scaling factor for the local CPE hybrid echo */    float near_cpe_hybrid_echo;    /*! The scaling factor for the local CO hybrid echo */    float near_co_hybrid_echo;    /*! The scaling factor for the far CPE hybrid echo */    float far_cpe_hybrid_echo;    /*! The scaling factor for the far CO hybrid echo */    float far_co_hybrid_echo;    /*! DC offset impairment */    float dc_offset;        /*! Mains pickup impairment */    int mains_interference;    tone_gen_state_t mains_tone;} one_way_line_model_state_t;/*!    Two way line model descriptor. This holds the complete state of    a line model with transmission in both directions.*/typedef struct{    one_way_line_model_state_t line1;    one_way_line_model_state_t line2;    float fout1;    float fout2; } both_ways_line_model_state_t;#ifdef __cplusplusextern "C"{#endifvoid both_ways_line_model(both_ways_line_model_state_t *s,                           int16_t output1[],                          const int16_t input1[],                          int16_t output2[],                          const int16_t input2[],                          int samples);void both_ways_line_model_set_dc(both_ways_line_model_state_t *s, float dc1, float dc2);void both_ways_line_model_set_mains_pickup(both_ways_line_model_state_t *s, int f, float level1, float level2);    both_ways_line_model_state_t *both_ways_line_model_init(int model1,                                                        float noise1,                                                        int model2,                                                        float noise2,                                                        int codec,                                                        int rbs_pattern);int both_ways_line_model_release(both_ways_line_model_state_t *s);void one_way_line_model(one_way_line_model_state_t *s,                         int16_t output[],                        const int16_t input[],                        int samples);void one_way_line_model_set_dc(one_way_line_model_state_t *s, float dc);void one_way_line_model_set_mains_pickup(one_way_line_model_state_t *s, int f, float level);one_way_line_model_state_t *one_way_line_model_init(int model, float noise, int codec, int rbs_pattern);int one_way_line_model_release(one_way_line_model_state_t *s);#ifdef __cplusplus}#endif#endif/*- End of file ------------------------------------------------------------*/