/*  ============================================================================   File: IIRFLT.H                                     Version: 3.0 - 31.JUL.95  ============================================================================                            UGST/ITU-T IIR FILTERS                          GLOBAL FUNCTION PROTOTYPES   History:   28.Feb.92	v1.0	First version <hf@pkinbg.uucp>   30.Oct.94	v2.0	Name changed to iirflt.h/included cascade-form                         IIR filters <simao@ctd.comsat.com>   31.Jul.95	v3.0	Added direct-form IIR filters <simao@ctd.comsat.com>  ============================================================================*/#ifndef IIRFLT_IIRstruct_defined#define IIRFLT_IIRstruct_defined  300/* DEFINITION FOR SMART PROTOTYPES */#ifndef ARGS#if (defined(__STDC__) || defined(VMS) || defined(__DECC)  || defined(MSDOS) || defined(__MSDOS__))#define ARGS(x) x#else /* Unix: no parameters in prototype! */#define ARGS(x) ()#endif#endif/* * ..... State variable structure for IIR filtering, parallel form  ..... */typedef struct{  long            nblocks;	/* number of coefficient sets         */  long            idown;	/* down sampling factor               */  long            k0;		/* start index in next segment        */  double          gain;		/* gain factor                        */  double          direct_cof;	/* In     : direct path coefficient   */  float           (*b)[3];	/* In     : numerator coefficients    */  float           (*c)[2];	/* In     : denominator coefficients  */  float           (*T)[2];	/* In/Out : state variables           */  char            hswitch;	/* "U": upsampling; else downsampling */}               SCD_IIR;/* * ..... State variable structure for IIR filtering, cascade form  ..... */typedef struct{  long            nblocks;	/* number of stages in cascade        */  long            idown;	/* down sampling factor               */  long            k0;		/* start index in next segment        */  double          gain;		/* gain factor                        */  float           (*a)[2];	/* In     : numerator coefficients    */  float           (*b)[2];	/* In     : denominator coefficients  */  float           (*T)[4];	/* In/Out : state variables, 1 for each stage*/  char            hswitch;	/* "U": upsampling; else downsampling */}               CASCADE_IIR;/* * ..... State variable structure for IIR filtering, direct form  ..... */typedef struct{  long            poleno;	/* number of poles                    */  long            zerono;	/* number of zeores                   */  long            idown;	/* down sampling factor               */  long            k0;		/* start index in next segment        */  double          gain;		/* gain factor                        */  float           *a;	        /* In     : numerator coefficients    */  float           *b;	        /* In     : denominator coefficients  */  float           (*T)[2];      /* In/Out : state variables           */  char            hswitch;	/* "U": upsampling; else downsampling */}               DIRECT_IIR;/* * ..... Global function prototypes ..... *//* Originals of the STL92: parallel IIR basic functions */long stdpcm_kernel ARGS((long lseg, float *x_ptr, SCD_IIR *iir_ptr, 			 float *y_ptr));void stdpcm_free ARGS((SCD_IIR *iir_ptr));void stdpcm_reset ARGS((SCD_IIR *iir_ptr));/* Originals of the STL92: parallel IIR filter initialization */SCD_IIR *stdpcm_16khz_init ARGS((void));SCD_IIR *stdpcm_2_to_1_init ARGS((void));SCD_IIR *stdpcm_1_to_2_init ARGS((void));/* Additions to the STL92: cascade IIR basic functions */long cascade_iir_kernel ARGS((long lseg, float *x_ptr, CASCADE_IIR *iir_ptr, 			      float *y_ptr));void cascade_iir_reset ARGS((CASCADE_IIR *iir_ptr));void cascade_iir_free ARGS((CASCADE_IIR *iir_ptr));/* Additions to the STL92: cascade IIR filter initialization */CASCADE_IIR *iir_G712_8khz_init ARGS((void));CASCADE_IIR *iir_irs_8khz_init ARGS((void));CASCADE_IIR *iir_casc_lp_3_to_1_init ARGS((void));CASCADE_IIR *iir_casc_lp_1_to_3_init ARGS((void));/* Additions to the STL92: direct IIR basic functions */long direct_iir_kernel ARGS((long lseg, float *x_ptr, DIRECT_IIR *iir_ptr, 			      float *y_ptr));void direct_reset ARGS((DIRECT_IIR *iir_ptr));void direct_iir_free ARGS((DIRECT_IIR *iir_ptr));/* Additions to the STL92: direct IIR filter initialization */DIRECT_IIR *iir_dir_dc_removal_init ARGS((void));#endif/* ........................... End of IIRFLT.H ........................... */