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iir-lib.c
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iir-lib.c
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/* v3.1 - 22/Feb/1996
=============================================================================
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
========================================
CCITT - USER'S GROUP ON SOFTWARE TOOLS
========================================
=============================================================
COPYRIGHT NOTE: This source code, and all of its derivations,
is subject to the "CCITT General Public License". Please have
it read in the distribution disk, or in the CCITT
Recommendation G.191 on "SOFTWARE TOOLS FOR SPEECH AND AUDIO
CODING STANDARDS".
=============================================================
MODULE: IIR-LIB.C, IIR FILTER MODULE
Sub-unit with basic filtering routines
ORIGINAL BY:
Rudolf Hofmann (Parallel form)
PHILIPS KOMMUNIKATIONS INDUSTRIE
Kommunikationssysteme Phone : +49 911 526-2603
Thurn-und-Taxis-Strasse 14 FAX : +49 911 526-3385
D-8500 Nuernberg 10 (Germany) EMail : hf@pkinbg.uucp
Simao Ferraz de Campos Neto (Cascade and direct form)
Comsat Laboratories Tel: +1-301-428-4516
22300 Comsat Drive Fax: +1-301-428-9287
Clarksburg MD 20871 - USA E-mail: simao@ctd.comsat.com
DESCRIPTION:
This file contains functions for running an IIR-filter with
coefficients in the parallel or the cascade (bi-quad) form.
FUNCTIONS : - stdpcm_kernel(...) = parallel-form IIR filter (kernel)
- stdpcm_reset(...) = clear parallel state variables
(needed only if another signal
should be processed with the
same filter)
- stdpcm_free(...) = deallocate parallel filter memory
- cascade_iir_kernel(...) = cascade-form IIR filter (kernel)
- cascade_iir_free(...) = deallocate cascade filter memory
- cascade_iir_reset(...) = clear cascade state variables
- direct_iir_kernel(...) = direct-form IIR filter (kernel)
- direct_iir_free(...) = deallocate direct filter memory
- direct_iir_reset(...) = clear direct state variables
HISTORY:
16.Dec.91 v0.1 First beta-version <hf@pkinbg.uucp>
28.Feb.92 v1.0 Release of 1st version to UGST <hf@pkinbg.uucp>
30.Oct.94 v2.0 Broken into sub-units; added cascade-form IIR filtering.
<simao@ctd.comsat.com>
31.Jul.95 v3.0 Added direct-form IIR filtering <simao@ctd.comsat.com>
22.Feb.96 v3.1 Changed inclusion of stdlib.h to inconditional, as
suggested by Kirchherr (FI/DBP Telekom) to run under
OpenVMS/AXP <simao@ctd.comsat.com>
=============================================================================
*/
/*
* ......... GENERAL INCLUDES .........
*/
#include <stdlib.h> /* General utility definitions */
#include <math.h> /* RTL Math Function Declarations */
/* Definitions for IIR filters */
#include "iirflt.h"
/*
* ......... Local function *smart* prototypes .........
*/
/* Parallel-form filtering basic function prototypes */
static long scd_parallel_form_iir_down_kernel ARGS((long lenx, float *x,
float *y, long *k0, long idown, long nblocks,
double direct_cof, double gain, float (*b)[3],
float (*c)[2], float (*T)[2]));
static long scd_parallel_form_iir_up_kernel ARGS((long lenx, float *x,
float *y, long iup, long nblocks, double direct_cof,
double gain, float (*b)[3], float (*c)[2],
float (*T)[2]));
SCD_IIR *scd_stdpcm_init ARGS((long nblocks, float (*b)[3], float (*c)[2],
double direct_cof, double gain, long idown,
int hswitch));
long cascade_iir_kernel ARGS((long lseg, float *x_ptr, CASCADE_IIR *iir_ptr,
float *y_ptr));
/* Cascade-form filtering basic function prototypes */
static long cascade_form_iir_down_kernel ARGS((long lenx, float *x, float *y,
long *k0, long idown, long nblocks, double gain,
float (*a)[2], float (*b)[2], float (*T)[4]));
static long cascade_form_iir_up_kernel ARGS((long lenx, float *x, float *y,
long iup, long nblocks, double gain, float (*a)[2],
float (*b)[2], float (*T)[4]));
CASCADE_IIR *cascade_iir_init ARGS((long nblocks, float (*a)[2], float (*b)[2],
double gain, long idown, int hswitch));
/* Direct-form filtering basic function prototypes */
long direct_iir_kernel ARGS((long lseg, float *x_ptr, DIRECT_IIR *iir_ptr,
float *y_ptr));
static long direct_form_iir_down_kernel ARGS((long lenx, float *x, float *y,
long *k0, long idown, long zno, long pno,
double gain, float *a, float *b, float (*T)[2]));
static long direct_form_iir_up_kernel ARGS((long lenx, float *x, float *y,
long iup, long zno, long pno, double gain,
float *a, float *b, float (*T)[2]));
DIRECT_IIR *direct_iir_init ARGS((long zno, long pno, float *a, float *b,
double gain, long idown, int hswitch));
/*
* ...................... BEGIN OF FUNCTIONS .........................
*/
/*
============================================================================
void stdpcm_free (SCD_IIR *iir_ptr);
~~~~~~~~~~~~~~~~
Description:
~~~~~~~~~~~~
Deallocate memory, which was allocated by an earlier call to one
of the initilization routines. `SCD_IIR *iir_prt' must not be
NULL.
Parameters:
~~~~~~~~~~~
SCD_IIR *iir_ptr: ... pointer to struct SCD_IIR previously
initialized by a call to one of the
initialization routines.
Return value:
~~~~~~~~~~~~~
Nothing.
Author: <hf@pkinbg.uucp>
~~~~~~~
History:
~~~~~~~~
28.Feb.92 v1.0 Release of 1st version <hf@pkinbg.uucp>
============================================================================
*/
void stdpcm_free(iir_ptr)
SCD_IIR *iir_ptr;
{
free(iir_ptr->T); /* free state variables */
free(iir_ptr); /* free allocated struct */
}
/* ....................... End of stdpcm_free() ....................... */
/*
============================================================================
void stdpcm_reset (SCD_IIR *iir_ptr);
~~~~~~~~~~~~~~~~~
Description:
~~~~~~~~~~~~
Clear state variables in SCD_IIR structure, which have been
initialized by a previous call to one of the init functions.
Parameters:
~~~~~~~~~~~
SCD_IIR *iir_ptr: ... pointer to struct SCD_IIR previously
initialized by a call to one of the
initialization routines.
Return value:
~~~~~~~~~~~~~
Nothing.
Author: <hf@pkinbg.uucp>
~~~~~~~
History:
~~~~~~~~
28.Feb.92 v1.0 Release of 1st version <hf@pkinbg.uucp>
============================================================================
*/
void stdpcm_reset(iir_ptr)
SCD_IIR *iir_ptr;
{
long n;
float (*T_ptr)[2];
T_ptr = iir_ptr->T;
for (n = 0; n < iir_ptr->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 stdpcm_reset() ....................... */
/*
============================================================================
SCD_IIR *scd_stdpcm_init (long nblocks, float (*b)[3],
~~~~~~~~~~~~~~~~~~~~~~~~ float (*c)[2], double direct_cof,
double gain, long idwnup,
char hswitch);
Description:
~~~~~~~~~~~~
Allocate&initialize struct for parallel IIR down/up-sampling functions.
Parameters:
~~~~~~~~~~~
long nblocks: ....... number of 2'nd order blocks
float (*b)[3]: ...... pointer to numerator coeffic.
float (*c)[3]: ...... pointer to denominator coeffic.
double direct_cof: .. direct path gain factor
double gain: ........ gain factor for filter
long idown: ......... Down-sampling factor
char hswitch: ....... to up-/downsampling routine
Return value:
~~~~~~~~~~~~~
Returns a pointer to struct SCD_IIR;
Author: <hf@pkinbg.uucp>
~~~~~~~
History:
~~~~~~~~
28.Feb.92 v1.0 Release of 1st version <hf@pkinbg.uucp>
30.Oct.94 v2.0 Made visible (not static) after module broken into
several sub-units <simao@ctd.comsat.com>
============================================================================
*/
SCD_IIR *scd_stdpcm_init(nblocks, b, c, direct_cof, gain, idown, hswitch)
long nblocks;
float (*b)[3], (*c)[2];
double direct_cof, gain;
long idown;
char hswitch;
{
static SCD_IIR *ptrIIR; /* pointer to the new struct */
float fak;
float (*T_ptr)[2];
long n;
/* Allocate memory for a new struct */
if ((ptrIIR = (SCD_IIR *) malloc((long) sizeof(SCD_IIR))) == (SCD_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->nblocks = nblocks; /* store number of 2'nd order blocks */
ptrIIR->b = b;
ptrIIR->c = c;
/* store down-sampling factor/gain/direct-path coefficient */
ptrIIR->idown = idown;
ptrIIR->gain = gain;
ptrIIR->direct_cof = direct_cof;
/* 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;
T_ptr[n][1] = 0.0;
}
ptrIIR->k0 = idown; /* modulo counter for down-sampling */
/* Exit returning pointer to struct */
return (ptrIIR);
}
/* ....................... End of scd_stdpcm_init() ....................... */
/*
============================================================================
long stdpcm_kernel (long lseg, float *x_ptr, SCD_IIR *iir_ptr,
~~~~~~~~~~~~~~~~~~ float *y_ptr);
Description:
~~~~~~~~~~~~
Standard PCM-filter.
Parameters:
~~~~~~~~~~~
lseg: ...... number of input samples
x_ptr: ..... array with input samples
iir_ptr: ... pointer to IIR-struct (SCD_IIR *)
y_ptr: ..... output samples
Return value:
~~~~~~~~~~~~~
Returns the number of output samples.
Author: <hf@pkinbg.uucp>
~~~~~~~
History:
~~~~~~~~
28.Feb.92 v1.0 Release of 1st version <hf@pkinbg.uucp>
============================================================================
*/
long stdpcm_kernel(lseg, x_ptr, iir_ptr, y_ptr)
long lseg;
float *x_ptr;
SCD_IIR *iir_ptr;
float *y_ptr;
{
if (iir_ptr->hswitch == 'U')
return
scd_parallel_form_iir_up_kernel( /* returns number of output samples */
lseg, /* In : length of input
* signal */
x_ptr, /* In : array with input
* samples */
y_ptr, /* Out : array with output
* samples */
iir_ptr->idown, /* In : downsampling
* factor */
iir_ptr->nblocks, /* In : number of
* IIR-coefficients */
iir_ptr->direct_cof,/* In: direct path
* coefficient */
iir_ptr->gain, /* In : gain factor */
iir_ptr->b, /* In : direct path
* coefficient */
iir_ptr->c, /* In : array with
* IIR-coefficients */
iir_ptr->T /* InOut: state
* variables */
);
else
return
scd_parallel_form_iir_down_kernel( /* returns number of output
* samples */
lseg, /* In : length of input
* signal */
x_ptr, /* In : array with input
* samples */
y_ptr, /* Out : array with output
* samples */
&(iir_ptr->k0), /* InOut:starting index
* in x-array */
iir_ptr->idown, /* In : downsampling
* factor */
iir_ptr->nblocks,/* In : number of
* IIR-coefficients */
iir_ptr->direct_cof,/* In : direct path
* coefficient */
iir_ptr->gain, /* In : gain factor */
iir_ptr->b, /* In : direct path
* coefficient */
iir_ptr->c, /* In : array w/
* IIR-coefficients */
iir_ptr->T /* InOut: state
* variables */
);
}
/* ....................... End of stdpcm_kernel() ....................... */
/*
============================================================================
long scd_parallel_form_iir_down_kernel(long lenx, float *x,
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ float *y, long *k0,
long idown, long nblocks,
double direct_cof,
double gain, float (*b)[3],
float (*c)[2], float (*T)[2]);
Description:
~~~~~~~~~~~~
Function for filtering a sequence of input samples by a
parallel-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
nblocks: ..... (In) number of coeff. sets
direct_cof: .. (In) direct path coefficient
gain: ........ (In) gain factor
b: ........... (In) numerator coefficients
c: ........... (In) denominator coefficients
T: ........... (In/Out) state variables
Return value:
~~~~~~~~~~~~~
Returns the number of samples filtered.
Author: <hf@pkinbg.uucp>
~~~~~~~
History:
~~~~~~~~
28.Feb.92 v1.0 Release of 1st version <hf@pkinbg.uucp>
============================================================================
*/
static long scd_parallel_form_iir_down_kernel(lenx, x, y, k0, idown,
nblocks, direct_cof, gain, b, c, T)
long lenx;
float *x, *y;
long *k0, idown, nblocks;
double direct_cof, gain;
float (*b)[3], (*c)[2], (*T)[2];
{
long kx, ky, n;
float Ttmp;
ky = 0; /* starting index in output array (y) */
for (kx = 0; kx < lenx; kx++) /* loop over all input samples */
{
if (*k0 % idown == 0) /* compute output only every "idown"
* samples */
{
y[ky] = direct_cof * x[kx]; /* direct path */
for (n = 0; n < nblocks; n++) /* loop over all second order filter */
{
Ttmp = 2. * (x[kx] - c[n][0] * T[n][0] - c[n][1] * T[n][1]);
y[ky] += b[n][2] * Ttmp + b[n][1] * T[n][1] + b[n][0] * T[n][0];
T[n][0] = T[n][1];
T[n][1] = Ttmp;
}
y[ky] *= gain;
ky++;
}
else
{
for (n = 0; n < nblocks; n++)
{
Ttmp = 2. * (x[kx] - c[n][0] * T[n][0] - c[n][1] * T[n][1]);
T[n][0] = T[n][1];
T[n][1] = Ttmp;
}
}
(*k0)++;
}
*k0 %= idown; /* avoid overflow by (*k0)++ */
return ky;
}
/* .............. End of scd_parallel_form_iir_down_kernel() .............. */
/*
============================================================================
long scd_parallel_form_iir_up_kernel(long lenx, float *x,
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ float *y, long *k0,
long idown, long nblocks,
double direct_cof,
double gain, float (*b)[3],
float (*c)[2], float (*T)[2]);
Description:
~~~~~~~~~~~~
Function for filtering a sequence of input samples by a
parallel-form IIR-filter with up-sampling.
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
nblocks: ..... (In) number of coeff. sets
direct_cof: .. (In) direct path coefficient
gain: ........ (In) gain factor
b: ........... (In) numerator coefficients
c: ........... (In) denominator coefficients
T: ........... (In/Out) state variables
Return value:
~~~~~~~~~~~~~
Returns the number of samples filtered.
Author: <hf@pkinbg.uucp>
~~~~~~~
History:
~~~~~~~~
28.Feb.92 v1.0 Release of 1st version <hf@pkinbg.uucp>
============================================================================
*/
static long scd_parallel_form_iir_up_kernel(lenx, x, y, iup, nblocks,
direct_cof, gain, b, c, T)
long lenx;
float *x, *y;
long iup, nblocks;
double direct_cof, gain;
float (*b)[3], (*c)[2], (*T)[2];
{
long kx, ky, n;
float Ttmp;
kx = 0; /* starting index in input array (x) */
for (ky = 0; ky < iup * lenx; ky++) /* loop over all input samples */
{
if (ky % iup == 0) /* compute output only every "iup" */
{ /* samples by taking one input sample */
y[ky] = direct_cof * x[kx]; /* direct path */
for (n = 0; n < nblocks; n++) /* loop over all second order filter */
{
Ttmp = 2. * (x[kx] - c[n][0] * T[n][0] - c[n][1] * T[n][1]);
y[ky] += b[n][2] * Ttmp + b[n][1] * T[n][1] + b[n][0] * T[n][0];
T[n][0] = T[n][1];
T[n][1] = Ttmp;
}
y[ky] *= gain;
kx++;
}
else
{
y[ky] = 0.0; /* at other instants feed zero-valued
* samples */
for (n = 0; n < nblocks; n++)
{
Ttmp = 2. * (0.0 - c[n][0] * T[n][0] - c[n][1] * T[n][1]);
y[ky] += b[n][2] * Ttmp + b[n][1] * T[n][1] + b[n][0] * T[n][0];
T[n][0] = T[n][1];
T[n][1] = Ttmp;
}
y[ky] *= gain;
}
}
return ky;
}
/* ............... End of scd_parallel_form_iir_up_kernel() ............... */
/* *************************************************************************
******** THE ROUTINES TO FOLLOW HAVE BEEN ADDED AFTER THE STL92 *********
* ************************************************************************* */
/*
============================================================================
void cascade_iir_reset (CASCADE_IIR *iir_ptr);
~~~~~~~~~~~~~~~~~~~~~~
Description:
~~~~~~~~~~~~
Clear state variables in CASCADE_IIR structure, what has been
initialized by a previous call to one of the init functions.
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_reset(iir_ptr)
CASCADE_IIR *iir_ptr;
{
long n;
float (*T_ptr)[4];
T_ptr = iir_ptr->T;
for (n = 0; n < iir_ptr->nblocks; n++)
{
T_ptr[n][0] = 0.0;
T_ptr[n][1] = 0.0;
T_ptr[n][2] = 0.0;
T_ptr[n][3] = 0.0;
}
iir_ptr->k0 = iir_ptr->idown; /* modulo counter for down-sampling */
}
/* .................... End of cascade_iir_reset() ...................... */
/*
============================================================================
long cascade_iir_kernel (long lseg, float *x_ptr, CASCADE_IIR *iir_ptr,
~~~~~~~~~~~~~~~~~~~~~~~ float *y_ptr);
Description:
~~~~~~~~~~~~
Basic cascade-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 (CASCADE_IIR *)
y_ptr: ..... output samples
Return value:
~~~~~~~~~~~~~
Returns the number of output samples.
Author: <simao@ctd.comsat.com>
~~~~~~~
History:
~~~~~~~~
30.Oct.94 v1.0 Release of 1st version <simao@ctd.comsat.com>
============================================================================
*/
long cascade_iir_kernel(lseg, x_ptr, iir_ptr, y_ptr)
long lseg;
float *x_ptr;
CASCADE_IIR *iir_ptr;
float *y_ptr;
{
if (iir_ptr->hswitch == 'U')
return
cascade_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->nblocks, /*In: no.IIR-coeffs */
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
cascade_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->nblocks, /*In:no.of IIR-coeffs */
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 cascade_iir_kernel() ....................... */
/*
============================================================================
long cascade_form_iir_down_kernel(long lenx, float *x,
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ float *y, long *k0,
long idown, long nblocks,
double gain, float (*a)[2],
float (*b)[2], float (*T)[4]);
Description:
~~~~~~~~~~~~
Function for filtering a sequence of input samples by a
cascade-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
nblocks: ..... (In) number of coeff. sets
gain: ........ (In) gain factor
b: ........... (In) numerator coefficients
c: ........... (In) denominator coefficients
T: ........... (In/Out) state variables
Return value:
~~~~~~~~~~~~~
Returns the number of samples filtered.
Author: <simao@ctd.comsat.com>
~~~~~~~
History:
~~~~~~~~
30.Oct.94 v1.0 Release of 1st version <simao@ctd.comsat.com>
============================================================================
*/
static long cascade_form_iir_down_kernel(lenx, x, y, k0, idown,
nblocks, gain, a, b, T)
long lenx;
float *x, *y;
long *k0, idown, nblocks;
double gain;
float (*a)[2], (*b)[2], (*T)[4];
{
long kx, ky, n;
double xj,yj;
ky = 0; /* starting index in output array (y) */
for (kx = 0; kx < lenx; kx++) /* loop over all input samples */
{
xj = x[kx]; /* direct path */
for (n = 0; n < nblocks; n++) /* loop over all second order filter */
{
yj = xj + a[n][0] * T[n][0] + a[n][1] * T[n][1];
yj -= (b[n][0] * T[n][2] + b[n][1] * T[n][3]);
/* Save samples in memory */
T[n][1] = T[n][0];
T[n][0] = xj;
T[n][3] = T[n][2];
T[n][2] = yj;
/* The yj of this stage is the xj of the next */
xj = yj;
}
if (*k0 % idown == 0) /* compute output only every "idown"
* samples */
{
/* Apply gain and update y-samples' counter */
y[ky] = yj * gain;
ky++;
}
(*k0)++;
}
*k0 %= idown; /* avoid overflow by (*k0)++ */
return ky;
}
/* .............. End of cascade_form_iir_down_kernel() .............. */
/*
============================================================================
long cascade_form_iir_up_kernel(long lenx, float *x,
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ float *y, long *k0,
long idown, long nblocks,
double gain, float (*a)[2],
float (*b)[2], float (*T)[4]);
Description:
~~~~~~~~~~~~
Function for filtering a sequence of input samples by a
cascade-form IIR-filter with up-sampling.
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
nblocks: ..... (In) number of coeff. sets
gain: ........ (In) gain factor
b: ........... (In) numerator coefficients
c: ........... (In) denominator coefficients
T: ........... (In/Out) state variables
Return value:
~~~~~~~~~~~~~
Returns the number of samples filtered.
Author: <simao@ctd.comsat.com>
~~~~~~~
History:
~~~~~~~~
30.Oct.94 v1.0 Release of 1st version <simao@ctd.comsat.com>
============================================================================
*/
static long cascade_form_iir_up_kernel(lenx, x, y, iup, nblocks,
gain, a, b, T)
long lenx;
float *x, *y;
long iup, nblocks;
double gain;
float (*a)[2], (*b)[2], (*T)[4];
{
long kx, ky, n;
double xj, 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 */
if (ky % iup == 0)
xj = x[kx];
else
xj = 0.;
/* Filter samples through all cascade stages */
for (n = 0; n < nblocks; n++)
{
yj = xj + a[n][0] * T[n][0] + a[n][1] * T[n][1];
yj -= (b[n][0] * T[n][2] + b[n][1] * T[n][3]);
/* Save samples in memory */
T[n][1] = T[n][0];
T[n][0] = xj;
T[n][3] = T[n][2];
T[n][2] = yj;
/* The yj of this stage is the xj of the next */
xj = yj;
}
/* Apply the gain and update x counter if needed */
y[ky] = yj * gain;
if (ky % iup == 0) kx++;
}
return ky;
}
/* ............... End of cascade_form_iir_up_kernel() ............... */
/*
============================================================================
CASCADE_IIR *cascade_iir_init (long nblocks, float (*a)[2],
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ float (*b)[2], double gain,
long idwnup, char hswitch);
Description:
~~~~~~~~~~~~
Allocate & initialize struct for down/up-sampling procedures.
Parameters:
~~~~~~~~~~~
long nblocks: ....... number of 2'nd order blocks
float (*a)[2]: ...... pointer to numerator coeffic.
float (*b)[2]: ...... 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 CASCADE_IIR;
Author: <simao@ctd.comsat.com>
~~~~~~~
History:
~~~~~~~~
30.Oct.94 v1.0 Release of 1st version <simao@ctd.comsat.com>
============================================================================
*/
CASCADE_IIR *cascade_iir_init(nblocks, a, b, gain, idown, hswitch)
long nblocks;
float (*a)[2], (*b)[2];
double gain;
long idown;
char hswitch;
{
static CASCADE_IIR *ptrIIR; /* pointer to the new struct */
float fak;
float (*T_ptr)[4];
long n;
/* Allocate memory for a new struct */
ptrIIR = (CASCADE_IIR *) malloc((long) sizeof(CASCADE_IIR));
if (ptrIIR == (CASCADE_IIR *) 0L)
{
return 0;
}
/* Allocate memory for state variables */
if ((ptrIIR->T = (float (*)[4]) malloc((nblocks * 4) * sizeof(fak)))
== (float (*)[4]) 0)
{
free(ptrIIR);
return 0;
}
/* fill coefficient sets */
ptrIIR->nblocks = nblocks; /* store number of 2'nd order blocks */
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;
T_ptr[n][1] = 0.0;
T_ptr[n][2] = 0.0;
T_ptr[n][3] = 0.0;
}
ptrIIR->k0 = idown; /* modulo counter for down-sampling */
/* Exit returning pointer to struct */
return (ptrIIR);
}
/* ....................... End of cascade_iir_init() ....................... */
/*
============================================================================
void cascade_free (CASCADE_IIR *iir_ptr);
~~~~~~~~~~~~~~~~~
Description:
~~~~~~~~~~~~