filter-butterworh-c

Simple Chebyshev and Butterworth implementation in C, double precision. Works well on macOS 13.4.1.

Features

• lowpass
• highpass
• butterworth
• chebyshev
• ripple percent

This imlementation is based on algorithm from https://exstrom.com/journal/sigproc/dsigproc.html

Run example

make example

./example

Steps to use a filter

Create a filter object using create_***_pass_filter(params...)

ChebFilter* filter = create_bw_low_pass_filter(ORDER, FC);

If fc is the cut-off frequency in hertz, the filter cut-off frequency must be expressed by fc/framerate. FC should be included in the [0, 0.5] range, 0.5 matching the Nyquist frequency.

FC=(double)fc/FR

For example, with a framerate at 44100Hz and a fc= 200Hz:

FC=(double)200/44100

Run the filter:

double filtered_signal = applyfilter(filter, input[i]);

Use filter to filter incoming doubles one by one. The filtered output is a double as well.

After using the filter, release the filter.

free(filter);