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)