}/* ....................... End of cascade_iir_init() ....................... *//*  ============================================================================  void cascade_free (CASCADE_IIR *iir_ptr);  ~~~~~~~~~~~~~~~~~  Description:  ~~~~~~~~~~~~  Deallocate memory, which was allocated by an earlier call to one  of the initilization routines. `CASCADE_IIR *iir_prt' must not be  NULL.  Parameters:  ~~~~~~~~~~~  CASCADE_IIR *iir_ptr: ... pointer to struct CASCADE_IIR previously                            initialized by a call to one of the                            initialization routines.  Return value:  ~~~~~~~~~~~~~  Nothing.  Author: <simao@ctd.comsat.com>  ~~~~~~~    History:  ~~~~~~~~  30.Oct.94 v1.0 Release of 1st version <simao@ctd.comsat.com> ============================================================================*/void            cascade_iir_free(iir_ptr)  CASCADE_IIR        *iir_ptr;{  free(iir_ptr->T);		  /* free state variables */  free(iir_ptr);		  /* free allocated struct */}/* ....................... End of cascade_iir_free() ....................... *//* *********************************************************************** *//*  ============================================================================  void direct_reset (DIRECT_IIR *iir_ptr);  ~~~~~~~~~~~~~~~~~    Description:  ~~~~~~~~~~~~  Clear state variables in DIRECT_IIR structure, what has been  initialized by a previous call to one of the init functions.  Parameters:  ~~~~~~~~~~~  DIRECT_IIR *iir_ptr: ... pointer to struct DIRECT_IIR previously                            initialized by a call to one of the initialization                            routines.  Return value:  ~~~~~~~~~~~~~  Nothing.  Author: <simao@ctd.comsat.com>  ~~~~~~~  History:  ~~~~~~~~  31.Jul.95 v1.0 Release of 1st version <simao@ctd.comsat.com> ============================================================================*/void            direct_reset(iir_ptr)  DIRECT_IIR        *iir_ptr;{  long            n;  register float  (*T_ptr)[2];  long nblocks = (iir_ptr->poleno > iir_ptr->zerono)                     ? iir_ptr->poleno                      : iir_ptr->zerono;  T_ptr = iir_ptr->T;  for (n = 0; n < nblocks; n++)  {    T_ptr[n][0] = 0.0;    T_ptr[n][1] = 0.0;  }  iir_ptr->k0 = iir_ptr->idown;	  /* modulo counter for down-sampling */}/* ....................... End of direct_reset() ....................... *//*  ============================================================================  long direct_iir_kernel (long lseg, float *x_ptr, DIRECT_IIR *iir_ptr,  ~~~~~~~~~~~~~~~~~~~~~~~  float *y_ptr);  Description:  ~~~~~~~~~~~~  Basic direct-form IIR filtering routine, for both up- and   down-sampling.  Parameters:  ~~~~~~~~~~~  lseg: ...... number of input samples  x_ptr: ..... array with input samples  iir_ptr: ... pointer to IIR-struct (DIRECT_IIR *)  y_ptr: ..... output samples  Return value:  ~~~~~~~~~~~~~  Returns the number of output samples.    Author: <simao@ctd.comsat.com>  ~~~~~~~    History:  ~~~~~~~~  31.Jul.95 v1.0 Release of 1st version <simao@ctd.comsat.com> ============================================================================*/long            direct_iir_kernel(lseg, x_ptr, iir_ptr, y_ptr)  long            lseg;  float          *x_ptr;  DIRECT_IIR    *iir_ptr;  float          *y_ptr;{  if (iir_ptr->hswitch == 'U')    return      direct_form_iir_up_kernel( /* returns number of output samples */				lseg,	          /* In : input signal leng. */				x_ptr,	  /* In : input sample array */				y_ptr,	  /* Out: outp. sample array */				iir_ptr->idown, /* In : dwnsmpl.factor */				iir_ptr->zerono, /*In: no.IIR-zeroes */				iir_ptr->poleno, /*In: no.IIR-poles */				iir_ptr->gain,  /* In : gain factor*/				iir_ptr->a,	  /* In : num.coeffs */				iir_ptr->b,	  /* In : denom.coeffs */				iir_ptr->T	  /* I/O: state vars */				);  else    return      direct_form_iir_down_kernel(/* returns number of output samples */				  lseg,	  /* In : input signal leng. */				  x_ptr,	  /* In : input sample array */				  y_ptr,	  /* Out: outp. sample array */				  &(iir_ptr->k0), /*I/O: start idx,x-array */				  iir_ptr->idown, /*In : dwnsmpl.factor */				  iir_ptr->zerono, /*In: no.IIR-zeroes */				  iir_ptr->poleno, /*In: no.IIR-poles */				  iir_ptr->gain, /* In : gain factor */				  iir_ptr->a,	  /* In : numerator coeffs */				  iir_ptr->b,	  /* In : denom.coeffs */				  iir_ptr->T	  /* I/O: state vars */				  );}/* .................... End of direct_iir_kernel() ....................... *//*  ============================================================================  long direct_form_iir_down_kernel(long lenx, float *x,  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ float *y, long *k0,                                    long idown, long zerono, long poleno,                                    double gain, float *a,                                    float *b, float (*T)[2]);    Description:  ~~~~~~~~~~~~  Function for filtering a sequence of input samples by a  direct-form IIR-filter with down-sampling.    Parameters:  ~~~~~~~~~~~  lenx: ........ (In) length of input array x[]  x: ........... (In) array with input samples  y: ........... (Out) array with output samples  k0: .......... (In/Out) pointer to modulo counter  idown: ....... (In) down-sampling factor  zerono: ...... (In) number of zeroes  poleno: ...... (In) number of poles  gain: ........ (In) gain factor  b: ........... (In) numerator coefficients  c: ........... (In) denominator coefficients  T: ........... (In/Out) past sample memory: T[][0] store past numerator (x)                       samples and T[][1] stores past denominator (y) samples.                       T[0][0],T[0][1] are the most recent samples,                       T[zerono-1][0],T[poleno-1][1] are the oldest.  Return value:  ~~~~~~~~~~~~~  Returns the number of samples filtered.  Author: <simao@ctd.comsat.com>  ~~~~~~~  History:  ~~~~~~~~  31.Jul.95 v1.0 Release of 1st version <simao@ctd.comsat.com> ============================================================================*/static long     direct_form_iir_down_kernel(lenx, x, y, k0, idown,                                              zerono, poleno, gain, a, b, T)  long            lenx;  float          *x, *y;  long           *k0, idown, zerono, poleno;  double          gain;  float           *a, *b, (*T)[2];{  long            kx, ky, n;  double   yj;  ky = 0;			  /* starting index in output array (y) */  for (kx = 0; kx < lenx; kx++)	  /* loop over all input samples */  {    /* Save xk in memory */    T[0][0] = x[kx];     /* Filter samples through numerator (zero) part */    for (yj=0, n = 0; n < zerono; n++)          yj +=  a[n] * T[n][0];    /* Filter samples through denominator (pole) part */    for (n = 1; n < poleno; n++)          yj -= b[n] * T[n-1][1];    /* Shift samples in memory (to the right) for next step */    for (n = zerono-1; n >0; n--)          T[n][0] = T[n-1][0];    for (n = poleno-1; n >0; n--)          T[n][1] = T[n-1][1];    T[0][1] = yj;    /* Save to output only every "idown" samples */    if (*k0 % idown == 0)    {      /* Apply gain and update y-samples' counter */      y[ky] = yj * gain;      ky++;    }    (*k0)++;  }  *k0 %= idown;			  /* avoid overflow by (*k0)++ */  return ky;}/* .............. End of direct_form_iir_down_kernel() .............. *//*  ============================================================================  long direct_form_iir_up_kernel(long lenx, float *x,  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ float *y, long *k0,                                  long idown, long zerono, long poleno,                                  double gain, float *a,                                  float *b, float (*T)[2]);  Description:  ~~~~~~~~~~~~  Function for filtering a sequence of input samples by a  direct-form IIR-filter with up-sampling. Samples are taken from the   input vector x only once-in-idown times; in the other times, the input   sample is zero (interpolation process).   Parameters:  ~~~~~~~~~~~  lenx: ........ (In) length of input array x[]  x: ........... (In) array with input samples  y: ........... (Out) array with output samples  iup: ......... (In) up-sampling factor  zerono: ...... (In) number of zeroes  poleno: ...... (In) number of poles  gain: ........ (In) gain factor  b: ........... (In) numerator coefficients  c: ........... (In) denominator coefficients  T: ........... (In/Out) past sample memory: T[][0] store past numerator (x)                       samples and T[][1] stores past denominator (y) samples.                       T[0][0],T[0][1] are the most recent samples,                       T[zerono-1][0],T[poleno-1][1] are the oldest.  Return value:  ~~~~~~~~~~~~~  Returns the number of samples filtered.    Author: <simao@ctd.comsat.com>  ~~~~~~~    History:  ~~~~~~~~  31.Jul.95 v1.0 Release of 1st version <simao@ctd.comsat.com> ============================================================================*/static long     direct_form_iir_up_kernel(lenx, x, y, iup, zerono, poleno,					   gain, a, b, T)  long            lenx;  float          *x, *y;  long            iup, zerono, poleno;  double          gain;  float           *a, *b, (*T)[2];{  long            kx, ky, n;  register double yj;  kx = 0;			  /* starting index in input array (x) */  for (ky = 0; ky < iup * lenx; ky++)	/* loop over all input samples */  {    /* Compute output only every "iup" compute output only every "iup"      * samples by taking one input sample direct path OR by using a      * zero-valued sample; already save on memory array */    T[0][0] = (ky % iup == 0) ? x[kx] : 0;    /* Filter samples through numerator (zero) part */    for (yj=0, n = 0; n < zerono; n++)          yj +=  a[n] * T[n][0];    /* Filter samples through denominator (pole) part */    for (n = 1; n < poleno; n++)          yj -= b[n] * T[n-1][1];    /* Shift samples in memory (to the right) for next step */    for (n = zerono-1; n >0; n--)          T[n][0] = T[n-1][0];    for (n = poleno-1; n >0; n--)          T[n][1] = T[n-1][1];    T[0][1] = yj;    /* Apply the gain and update x counter if needed */    y[ky] = yj * gain;    if (ky % iup == 0) kx++;  }  return ky;}/* ............... End of direct_form_iir_up_kernel() ............... *//*  ============================================================================  DIRECT_IIR *direct_iir_init (long nblocks, float *a,  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  float *b, double gain, 	                         long idwnup, char hswitch);  Description:  ~~~~~~~~~~~~  Allocate & initialize struct for down/up-sampling procedures.  Parameters:  ~~~~~~~~~~~  long zerono: ........ number of zeroes  long poleno: ........ number of poles  float *a: ........... pointer to numerator coeffic.  float *b: ........... pointer to denominator coeffic.  double gain: ........ gain factor for filter  long idown: ......... Down-sampling factor  char hswitch: ....... to up-/downsampling routine  Return value:  ~~~~~~~~~~~~~  Returns a pointer to struct DIRECT_IIR;  Author: <simao@ctd.comsat.com>  ~~~~~~~    History:  ~~~~~~~~  31.Jul.95 v1.0 Release of 1st version <simao@ctd.comsat.com> ============================================================================*/DIRECT_IIR *direct_iir_init(zerono, poleno, a, b, gain, idown, hswitch)  long            zerono, poleno;  float           *a, *b;  double          gain;  long            idown;  char            hswitch;{  static DIRECT_IIR *ptrIIR;	  /* pointer to the new struct */  float           fak;  float           (*T_ptr)[2];  long            n;  long nblocks;  /* Get greater of zero and pole */  nblocks = zerono > poleno? zerono: poleno;  /* Allocate memory for a new struct */  ptrIIR = (DIRECT_IIR *) malloc((long) sizeof(DIRECT_IIR));  if (ptrIIR == (DIRECT_IIR *) 0L)  {    return 0;  }  /* Allocate memory for state variables */  if ((ptrIIR->T = (float (*)[2]) malloc((nblocks * 2) * sizeof(fak)))      == (float (*)[2]) 0)  {    free(ptrIIR);    return 0;  }  /* fill coefficient sets */  ptrIIR->poleno = poleno;	  /* store number of poles */  ptrIIR->zerono = zerono;	  /* store number of zeroes */  ptrIIR->a = a;  ptrIIR->b = b;  /* store down-sampling factor/gain/direct-path coefficient */  ptrIIR->idown = idown;  ptrIIR->gain = gain;  /* Store switch to IIR-kernel procedure */  ptrIIR->hswitch = hswitch;  /* Clear state variables */  T_ptr = ptrIIR->T;  for (n = 0; n < nblocks; n++)  {    T_ptr[n][0] = 0.0; /* Numerator memory */    T_ptr[n][1] = 0.0; /* Denominator memory */  }  ptrIIR->k0 = idown;		  /* modulo counter for down-sampling */  /* Exit returning pointer to struct */  return (ptrIIR);}/* ....................... End of direct_iir_init() ....................... *//*  ============================================================================  void direct_free (DIRECT_IIR *iir_ptr);  ~~~~~~~~~~~~~~~~~  Description:  ~~~~~~~~~~~~  Deallocate memory, which was allocated by an earlier call to one  of the initilization routines. `DIRECT_IIR *iir_prt' must not be  NULL.  Parameters:  ~~~~~~~~~~~  DIRECT_IIR *iir_ptr: ... pointer to struct DIRECT_IIR previously                            initialized by a call to one of the                            initialization routines.  Return value:  ~~~~~~~~~~~~~  Nothing.  Author: <simao@ctd.comsat.com>  ~~~~~~~    History:  ~~~~~~~~  31.Jul.95 v1.0 Release of 1st version <simao@ctd.comsat.com> ============================================================================*/void            direct_iir_free(iir_ptr)  DIRECT_IIR        *iir_ptr;{  free(iir_ptr->T);		  /* free state variables */  free(iir_ptr);		  /* free allocated struct */}/* ....................... End of direct_iir_free() ....................... *//* **************************** END OF IIR-LIB.C ************************ */