1RTF_CREATE_DOWNSAMPLER(3)      rtfilter library      RTF_CREATE_DOWNSAMPLER(3)
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NAME

6       rtf_create_downsampler - Creates downsampling filter
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SYNOPSIS

9       #include <rtfilter.h>
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11       hfilter rtf_create_downsampler(unsigned int nch, int type,
12                                      unsigned int r);
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DESCRIPTION

15       rtf_create_downsampler() creates a filter that downsamples signals com‐
16       ing from nch channels of type type (see rtf_create_filter(3)) by a dec‐
17       imation factor of r (i.e. the sampling frequency of the input will be r
18       times the sampling frequency of the output). This  is  achieved  inter‐
19       nally  by applying a lowpass 4-order Chebychev filter to the input data
20       using a normalized cutoff frequency of  0.8/(2*r)  and  decimating  the
21       result every r samples.
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RETURN VALUE

24       Returns  the handle to the created filter in case of success, NULL oth‐
25       erwise.
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NOTES

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

34       rtf_filter(3), rtf_create_filter(3), rtf_destroy_filter(3)
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41EPFL                                 2010            RTF_CREATE_DOWNSAMPLER(3)
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