/*                                                         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:         CASCG712.C, IIR FILTER MODULE,                 Sub-unit with the cascade-form standard PCM filter (G.712)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 an        IIR-filter (cascade form) with a standard PCM frequency        response for only the sampling frequency 8 kHz.FUNCTIONS    : - iir_G712_8khz_init = initialization of cascade-form IIR G.712	       - fill_iir_G712_8khz = coeffs for cascade-form IIR G.712HISTORY:    30.Oct.94 v1.0 Release of 1st version <simao@ctd.comsat.com>  =============================================================================*/#ifndef VMS#include <stdlib.h>		  /* General utility definitions */#endif#include <stdio.h>		  /* UNIX Standard I/O Definitions */#include <math.h>		  /* RTL Math Function Declarations */#include "iirflt.h"/* Local function prototypes */void fill_iir_G712_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_G712_8khz ();  ~~~~~~~~~~~~~~~~~~~~~~~  Description:  ~~~~~~~~~~~~  Initialize pointer to arrays with IIR coefficients for IIR G712  filter, running at 8 kHz. The coefficients used were given  by John Rosenberger (Bellcore, USA), what 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_G712_8khz(a_cof, b_cof, nblocks)  float        ***a_cof;  float        ***b_cof;  long           *nblocks;{#define nblocks_8khz        2	  /* number of 2'nd order blocks */  /* Numerator coefficients */  static float a_G712_8khz[nblocks_8khz][2] =                            { /*       T[L]1   ,      T[L]2 */			     {0.197140840E+01, 0.100000000E+01},			     {-0.199301310E+01, 0.100000000E+01}			   };  /* Denominator coefficients */  static float  b_G712_8khz[nblocks_8khz][2] =                           { /*  T[L]3   ,      T[L]4 */			     {0.156814950E+01, 0.690445310E+00},			     {-0.179704400E+01, 0.830129300E+00}                           };  *nblocks = nblocks_8khz;  *a_cof = (float **) a_G712_8khz;  *b_cof = (float **) b_G712_8khz;}#undef nblocks_8khz/* ..................... End of fill_iir_G712_8khz() ...................... *//*  ============================================================================  CASCADE_IIR *iir_G712_8khz_init (void);  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~    Description:  ~~~~~~~~~~~~  Initialize a 8 kHz IIR filter structure for G712 (P.48) filtering.   Coefficients init'd by fill...() and gain furnished by Bellcore. The factor   for this function is 1:1.  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_G712_8khz_init(){  float         **a_cof, **b_cof; /* pointer to numerator/denominator */  long            nblocks;	  /* number of 2'nd order blocks */  fill_iir_G712_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. */			 0.695296250,  /* In: gain factor for filter */			 (long) 1,/* In: Down-sampling factor */			 'D');	  /* -> call down-sampling routine */}/* ...................... End of iir_G712_8khz_init() ...................... *//* ************************* END OF FILE CASCG712.C ************************ */