Rust: `no_std` digital low pass filter library

This is a no_std Rust library for simple digital low pass filters. You can use it for example to get the low frequencies from a song.

I'm not an expert on digital signal processing. Code contributions are highly welcome! :)

How to use

```rust use audiovisualizer::waveform::staticc::pngfile::waveformstaticpngvisualize; // audiovisualizer has some cool convenient types that I reuse here use audiovisualizer::{ChannelInterleavement, Channels}; use lowpassfilter::simple::sp::applylpfi16_sp;

/// Minimal example how to use this crate/how to apply low pass filter. fn main() { // read this from MP3 for example let audiodatalrlr = [0_i16, 1, -5, 1551, 141, 24];

// split into left and right channel
// audio_visualizer has some cool convenient types that I reuse here
let (mut left, mut right) = Channels::Stereo(ChannelInterleavement::LRLR)
    .stereo_interleavement()
    .to_channel_data(&audio_data_lrlr);

// left
apply_lpf_i16_sp(&mut left, 44100, 120);
// right
apply_lpf_i16_sp(&mut right, 44100, 120);

// visualize effect as waveform in a PNG file
waveform_static_png_visualize(
    &left,
    Channels::Mono,
    "test/out",
    "example_waveform_lowpassed_left.png",
);
waveform_static_png_visualize(
    &right,
    Channels::Mono,
    "test/out",
    "example_waveform_lowpassed_right.png",
);

} ```