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.
