NAME¶
rtf_create_fir_lowpass, rtf_create_fir_highpass, rtf_create_fir_bandpass -
Creates FIR lowpass, highpass and bandpass windowed sinc filters
SYNOPSIS¶
#include <rtf_common.h>
hfilter rtf_create_fir_lowpass(unsigned int nch, int
proctype,
double fc, unsigned int hlen,
KernelWindow wndtype);
hfilter rtf_create_fir_highpass(unsigned int nch, int
proctype,
double fc, unsigned int hlen,
KernelWindow wndtype);
hfilter rtf_create_fir_bandpass(unsigned int nchann, int
proctype,
double fc_low, double fc_high,
unsigned int hlen,
KernelWindow wndtype);
DESCRIPTION¶
rtf_create_fir_lowpass() creates a lowpass windowed sinc filter
processing
nchann channels of data type specified by
proctype
with
fc as normalized cutoff frequency and
hlen as the half
length of the window.
rtf_create_fir_highpass() is the same as
rtf_create_fir_lowpass()
but creates a highpass filter.
rtf_create_fir_bandpass() is the same but creates a bandpass filter with
fc_low and
fc_high as respectively the lowpass and highpass
normalized cutoff frequencies.
A normalized frequency is the ratio between the absolute frequency and the
sampling frequency (i.e. a value of 1.0 refers to the sampling frequency).
The parameter
proctype has the same meaning as in
rtf_create_filter(3). Refers to its manpage for more details.
The parameter
wndtype specifies the type of window applied to the impulse
response and can take the following values:
BLACKMAN_WINDOW,
HAMMING_WINDOW or
RECT_WINDOW (see a book on signal processing
for details about their meaning).
RETURN VALUE¶
Returns the handle to the created filter in case of success, NULL otherwise.
SEE ALSO¶
rtf_create_filter(3),
rtf_destroy_filter(3)