oracular (3) rtf_create_filter.3.gz

NAME

       rtf_create_filter - Creates a custom filter

SYNOPSIS

       #include <rtfilter.h>

       hfilter rtf_create_filter(unsigned int nchann, int proctype,
                                 unsigned int num_len, const void *num,
                                 unsigned int denum_len, const void *denum,
                                 int type);

DESCRIPTION

       This  function  creates  and  initializes  a  digital linear filter whose the Z-transform is rational and
       processing nchann channels of a data type specified by proctype.

       The numerator and denominator of the rational expression are specified by respectively two arrays num and
       denum  containing  the  coefficients  in the ascending order of the 2 polynoms. The number of elements in
       each arrays is controlled by num_len and enum_len.  denum_len is allowed to be equal to zero as  well  as
       denum is allowed to be NULL. In such case, the denominator will be set to 1.  The data type of the values
       in num and denum are specified by type.

       The proctype and type must be one the following constants:

          RTF_FLOAT specifies real single precision (float)

          RTF_DOUBLE specifies real double precision (double)

          RTF_CFLOAT specifies complex single precision (complex float)

          RTF_CDOUBLE specifies complex double precision (complex double)

       The expected data type of the output of the filter has  the  same  precision  as  the  one  specified  by
       proctype and is complex proctype or type specifies a complex type. Said otherwise:

        * If proctype is RTF_FLOAT or RTF_CFLOAT then the output data type will have single precision. Otherwise
          it will have double precision.

        * If proctype or type specifies a complex type, then the output will be complex as well.  Otherwise,  it
          will be real.

       rtf_create_filter()  can  be  used  to use a filter that has been designed somewhere else. In particular,
       this function can be used directly with the output of filter design function of MATLAB. In such case, the
       usual  B and A arrays returned by the filter design functions corresponds exactly to respectively num and
       denum.

RETURN VALUE

       Returns the handle to the created filter in case of success, NULL otherwise.

PERFORMANCE CONSIDERATION

       See note of rtf_filter(3)

SEE ALSO

       rtf_destroy_filter(3), rtf_init_filter(3), rtf_filter(3)