/*                                                         v1.0 30.OCT.94 18H00  =============================================================================                          U    U   GGG    SSSS  TTTTT                          U    U  G       S       T                          U    U  G  GG   SSSS    T                          U    U  G   G       S   T                           UUU     GG     SSS     T                   ========================================                    ITU-T - USER'S GROUP ON SOFTWARE TOOLS                   ========================================MODULE:         IIR-IRS.C, IIR FILTER MODULE, 		Sub-unit with IRS IIR filtering for data sampled at 8kHz.ORIGINAL BY:  Simao Ferraz de Campos Neto  Comsat Laboratories                  Tel:    +1-301-428-4516  22300 Comsat Drive                   Fax:    +1-301-428-9287  Clarksburg MD 20871 - USA            E-mail: simao@ctd.comsat.comDESCRIPTION:        This file contains functions for initializing and running an        IIR-filter (cascade form) with a standard IRS weighting        (sampling frequency = 8 kHz). FUNCTIONS    : - iir_irs_8khz_init = initialization of cascade-form IIR IRS	       - fill_iir_irs_8khz = coeffs for cascade-form IIR IRSHISTORY:    30.Oct.94 v1.0 Created <simao@ctd.comsat.com>  =============================================================================*//* General includes */#ifndef VMS#include <stdlib.h>		  /* General utility definitions */#endif#include <stdio.h>		  /* UNIX Standard I/O Definitions */#include <math.h>		  /* RTL Math Function Declarations *//* This module's prototypes */#include "iirflt.h"/* Local function prototypes */void fill_iir_irs_8khz ARGS((float ***a_cof, float ***b_cof, long *nblocks));/* External function prototypes - code in in iir-lib.c */extern CASCADE_IIR *cascade_iir_init ARGS((long nblocks, float (*a)[2], 			 float (*b)[2], double gain, long idown, int hswitch));/*  ============================================================================  void fill_iir_irs_8khz (float ***a_cof, float ***b_cof, long *nblocks);  ~~~~~~~~~~~~~~~~~~~~~~  Description:  ~~~~~~~~~~~~  Initialize pointer to arrays with IIR coefficients for IIR IRS filter,  running at 8 kHz. The coefficients used were given by John Rosenberger  (Bellcore, USA) for the ITU-T 8 kbit/s speech coder qualification tests.  The coefficients are of a filter in the cascade form.  Parameters:  ~~~~~~~~~~~  float ***a_cof .. pointer to numerator filter coefficients  float ***b_cof .. pointer to denominator filter coefficients  long *nblocks ... number of coefficients (output value)  Return value:  None.  ~~~~~~~~~~~~~  Author: <simao@ctd.comsat.com>  ~~~~~~~  History:  ~~~~~~~~  30.Sep.94 v1.0 Release of 1st version <simao> ============================================================================*/void            fill_iir_irs_8khz(a_cof, b_cof, nblocks)  float        ***a_cof;  float        ***b_cof;  long           *nblocks;{#define nblocks_8khz        8	  /* number of 2'nd order blocks */  /* Numerator coefficients */  static float a_irs_8khz[nblocks_8khz][2] =                            { /*       T[L]1   ,      T[L]2 */			     { 0.181181010E+01, -0.278533980E+01},			     {-0.341588540E+01,  0.241742110E+01},			     { 0.106290280E+01,  0.637687860E+00},			     {-0.114114690E+02,  0.105993240E+02},			     { 0.533929010E+01,  0.431985380E+01},			     {-0.174458730E+01, -0.110326430E+02},			     { 0.122531430E-01, -0.102518530E+01},			     {-0.288089440E-01, -0.995417300E+00}			   };  /* Denominator coefficients */  static float  b_irs_8khz[nblocks_8khz][2] =                           { /*  T[L]3   ,      T[L]4 */			     { 0.117483180E+00, -0.315495510E-01},			     {-0.176085970E+01,  0.803684710E+00},			     { 0.736577630E+00,  0.447875650E+00},			     {-0.110519770E+01,  0.425873550E+00},			     { 0.154399700E+01,  0.761976480E+00},			     {-0.189045870E+01,  0.910008010E+00},			     { 0.806640680E+00,  0.132415190E+00},			     { 0.105510470E+01,  0.522127990E+00}                           };  *nblocks = nblocks_8khz;  *a_cof = (float **) a_irs_8khz;  *b_cof = (float **) b_irs_8khz;}#undef nblocks_8khz/* ..................... End of fill_iir_irs_8khz() ...................... *//*  ============================================================================  CASCADE_IIR *iir_irs_8khz_init (void);  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  Description:  ~~~~~~~~~~~~  Initialize a 8 kHz IIR filter structure for IRS (P.48) filtering.   Coefficients init'd by fill...() & gain furnished by Bellcore for the  ITU-T 8 kbit/s speech coder qualification tests.  Parameters:  none.  ~~~~~~~~~~~  Return value:  ~~~~~~~~~~~~~  Returns a pointer to struct CASCADE_IIR;    Author: <simao@ctd.comsat.com>  ~~~~~~~  History:  ~~~~~~~~  30.Sep.94 v1.0 Release of 1st version <simao> ============================================================================*/CASCADE_IIR        *iir_irs_8khz_init(){  float         **a_cof, **b_cof; /* pointer to numerator/denominator */  long            nblocks;	  /* number of 2'nd order blocks */  fill_iir_irs_8khz		  /* get pointer to filter-coefficients */    (&a_cof, &b_cof, &nblocks);  return cascade_iir_init(	  /* Returns: pointer to CASCADE_IIR-struct */			 nblocks, /* In: number of 2'nd order blocks */			 (float (*)[2]) a_cof,	/* In: 24-bit repres. of						 * numer. coef. */			 (float (*)[2]) b_cof,	/* In: 24-bit repres. of						 * denom. coef. */			 1.05133050E-04,  /* In: gain factor for filter */			 (long) 1,/* In: Down-sampling factor */			 'D');	  /* -> call down-sampling routine */}/* ...................... End of iir_irs_8khz_init() ...................... *//* *************************** END OF IIR_IRS.C **************************** */