RTF_CREATE_FILTER(3)						 rtfilter library					      RTF_CREATE_FILTER(3)

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 corre-
       sponds 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)

EPFL
								       2010						      RTF_CREATE_FILTER(3)