Man page - rtf_create_downsampler(3)

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Manual

RTF_CREATE_DOWNSAMPLER

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
NOTES
SEE ALSO

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 .