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/**
* \file filterSupport.h
* \brief Filter support functions.
* \copyright Copyright (C) 2006-2022 Ralf Hoppe <ralf.hoppe@dfcgen.de>
*/
#ifndef FILTERSUPPORT_H
#define FILTERSUPPORT_H
/* INCLUDE FILES **************************************************************/
#include "dfcgen.h"
#ifdef __cplusplus
extern "C" {
#endif
/* GLOBAL TYPE DECLARATIONS ***************************************************/
/* GLOBAL CONSTANT DECLARATIONS ***********************************************/
/* GLOBAL VARIABLE DECLARATIONS ***********************************************/
/* GLOBAL MACRO DEFINITIONS ***************************************************/
#define FLTERR_CRITICAL(err) ((err) > 0)
#define FLTERR_WARNING(err) ((err) < 0)
#define FLTERR_SUCCESS(err) ((err) == 0)
/* EXPORTED FUNCTIONS *********************************************************/
/* FUNCTION *******************************************************************/
/** Allocates memory space for a filter.
*
* This function mallocs memory space for filter coefficients and roots based
* on the degree of numerator and denominator polynomial.
*
* \param flt Filter structure.
*
* \return 0 on success, else an error code (typically ENOMEM).
******************************************************************************/
int filterMalloc (FLTCOEFF *flt);
/* FUNCTION *******************************************************************/
/** Free's all memory space allocated for a filter.
*
* \param flt Filter structure.
*
******************************************************************************/
void filterFree(FLTCOEFF *flt);
/* FUNCTION *******************************************************************/
/** Duplicates a filter. This function mallocs memory space for filter
* coefficients and roots based on the degree of the source filter pointed by
* \p src. Then it copies the numerator and denominator polynomial to \p dest.
* Use function filterFree() to free all the new associated memory.
*
* \param src Source filter (input).
* \param dest Destination filter (output).
*
* \return Zero on success, else an error code (typically ENOMEM).
******************************************************************************/
int filterDuplicate (FLTCOEFF *dest, FLTCOEFF *src);
/* FUNCTION *******************************************************************/
/** Checks ability to implement a digital system/filter.
*
* \param pFilter Pointer to filter coefficients/roots.
*
* \return - 0 (or GSL_SUCCESS) if okay and nothing has changed.
* - a negative number (typically GSL_CONTINUE) if a
* coefficient or the degree has changed, but the filter
* is valid. You can use the FLTERR_WARNING macro from
* filterSupport.h to check this condition.
* - a positive error number (typically from from errno.h
* or gsl_errno.h) that something is wrong and the
* filter must be seen as invalid. You can use the
* FLTERR_CRITICAL macro from filterSupport.h to check
* this condition.
******************************************************************************/
int filterCheck (FLTCOEFF *pFilter);
/* FUNCTION *******************************************************************/
/** Normalizes the coefficients of a filter. To perform that, it
* first modifies the denominator coefficients such that \f$den_0=1\f$ is
* ensured. At the second step it re-calculates the numerator coefficients.
*
* \param pFilter Pointer to filter.
*
* \return - 0 (or GSL_SUCCESS) if okay and nothing has changed.
* - a negative number (typically GSL_CONTINUE) if a
* coefficient or the degree has changed, but the filter
* is valid. You can use the FLTERR_WARNING macro from
* filterSupport.h to check this condition.
* - a positive error number (typically from from errno.h
* or gsl_errno.h) that something is wrong and the
* filter must be seen as invalid. You can use the
* FLTERR_CRITICAL macro from filterSupport.h to check
* this condition.
******************************************************************************/
int normFilterCoeffs (FLTCOEFF *pFilter);
/* FUNCTION *******************************************************************/
/** Normalizes the magnitude of a filter. The function trys to normalize the
* transfer ratio (filter magnitude) at a given frequency. To perform that, it
* first modifies the denominator coefficients such that \f$den_0=1\f$ is
* ensured. At the second step it re-calculates the numerator coefficients in
* a way, that the magnitude response at the reference frequency is unity (1).
*
* \param pFilter Pointer to filter.
* \param f Frequency (normalization point).
* \param refgain Reference transfer ratio \f$H(2\pi f)\f$.
*
* \return - 0 (or GSL_SUCCESS) if okay and nothing has changed.
* - a negative number (typically GSL_CONTINUE) if a
* coefficient or the degree has changed, but the filter
* is valid. You can use the FLTERR_WARNING macro from
* filterSupport.h to check this condition.
* - a positive error number (typically from from errno.h
* or gsl_errno.h) that something is wrong and the
* filter must be seen as invalid. You can use the
* FLTERR_CRITICAL macro from filterSupport.h to check
* this condition.
******************************************************************************/
int normFilterMagnitude (FLTCOEFF *pFilter, double f, double refgain);
#ifdef __cplusplus
}
#endif
#endif /* FILTERSUPPORT_H */
/******************************************************************************/
/* END OF FILE */
/******************************************************************************/
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