rtf_create_downsampler(3) Creates downsampling filter


#include <rtfilter.h>

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


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.


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


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.