NAME

       rtf_create_downsampler - Creates downsampling filter

SYNOPSIS

       #include <rtfilter.h>

       hfilter rtf_create_downsampler(unsigned int nch, int type,
                                      unsigned int r);

DESCRIPTION

       rtf_create_downsampler()  creates  a  filter  that  downsamples  signals  coming  from nch
       channels of type type (see rtf_create_filter(3)) by a decimation factor  of  r  (i.e.  the
       sampling  frequency  of  the  input will be r times the sampling frequency of the output).
       This is achieved internally by applying a lowpass 4-order Chebychev filter  to  the  input
       data  using  a  normalized cutoff frequency of 0.8/(2*r) and decimating the result every r
       samples.

RETURN VALUE

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

NOTES

       On the contrary of most other filters, the number of samples returned by rtf_filter(3)  is
       different  than  the  input  (as expected) but also may vary at each call if the number of
       sample supplied in input is not a multiple of r.

SEE ALSO

       rtf_filter(3), rtf_create_filter(3), rtf_destroy_filter(3)