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#![deny(
clippy::all,
clippy::cargo,
clippy::nursery,
)]
#![allow(
clippy::suboptimal_flops,
clippy::redundant_pub_crate,
clippy::fallible_impl_from
)]
#![deny(missing_debug_implementations)]
#![deny(rustdoc::all)]
#![cfg_attr(not(test), no_std)]
extern crate alloc;
#[cfg_attr(test, macro_use)]
#[cfg(test)]
extern crate std;
pub fn lowpass_filter(data: &mut [f32], sampling_rate: f32, cutoff_frequency: f32) {
let rc = 1.0 / (cutoff_frequency * 2.0 * core::f32::consts::PI);
let dt = 1.0 / sampling_rate;
let alpha = dt / (rc + dt);
data[0] *= alpha;
for i in 1..data.len() {
data[i] = data[i - 1] + alpha * (data[i] - data[i - 1]);
}
}
pub fn lowpass_filter_f64(data: &mut [f64], sampling_rate: f64, cutoff_frequency: f64) {
let rc = 1.0 / (cutoff_frequency * 2.0 * core::f64::consts::PI);
let dt = 1.0 / sampling_rate;
let alpha = dt / (rc + dt);
data[0] *= alpha;
for i in 1..data.len() {
data[i] = data[i - 1] + alpha * (data[i] - data[i - 1]);
}
}
#[cfg(test)]
mod test_util;
#[cfg(test)]
mod tests {
use super::*;
use crate::test_util::{calculate_power, sine_wave_samples, TEST_OUT_DIR};
use audio_visualizer::waveform::plotters_png_file::waveform_static_plotters_png_visualize;
use audio_visualizer::Channels;
use biquad::{Biquad, Coefficients, DirectForm1, ToHertz, Type, Q_BUTTERWORTH_F64};
use std::time::Instant;
use std::vec::Vec;
#[test]
fn test_lpf_and_visualize() {
let samples_l_orig = sine_wave_samples(120.0, 44100.0);
let samples_h_orig = sine_wave_samples(350.0, 44100.0);
waveform_static_plotters_png_visualize(
&samples_l_orig.iter().map(|x| *x as i16).collect::<Vec<_>>(),
Channels::Mono,
TEST_OUT_DIR,
"test_lpf_l_orig.png",
);
waveform_static_plotters_png_visualize(
&samples_h_orig.iter().map(|x| *x as i16).collect::<Vec<_>>(),
Channels::Mono,
TEST_OUT_DIR,
"test_lpf_h_orig.png",
);
let mut samples_l_lowpassed = samples_l_orig.clone();
let mut samples_h_lowpassed = samples_h_orig.clone();
let power_l_orig = calculate_power(&samples_l_orig);
let power_h_orig = calculate_power(&samples_h_orig);
lowpass_filter_f64(samples_l_lowpassed.as_mut_slice(), 44100.0, 90.0);
lowpass_filter_f64(samples_h_lowpassed.as_mut_slice(), 44100.0, 90.0);
let power_l_lowpassed = calculate_power(&samples_l_lowpassed);
let power_h_lowpassed = calculate_power(&samples_h_lowpassed);
waveform_static_plotters_png_visualize(
&samples_l_lowpassed
.iter()
.map(|x| *x as i16)
.collect::<Vec<_>>(),
Channels::Mono,
TEST_OUT_DIR,
"test_lpf_l_after.png",
);
waveform_static_plotters_png_visualize(
&samples_h_lowpassed
.iter()
.map(|x| *x as i16)
.collect::<Vec<_>>(),
Channels::Mono,
TEST_OUT_DIR,
"test_lpf_h_after.png",
);
assert!(power_h_lowpassed < power_h_orig);
assert!(power_l_lowpassed < power_l_orig);
assert!(power_h_lowpassed <= 3.0 * power_h_lowpassed);
assert!(
power_h_lowpassed * 3.0 <= power_l_lowpassed,
"LPF must actively remove frequencies above threshold"
);
}
#[test]
fn test_lpf_f32_f64() {
let samples_h_orig = sine_wave_samples(350.0, 44100.0);
let mut lowpassed_f32 = samples_h_orig.iter().map(|x| *x as f32).collect::<Vec<_>>();
#[allow(clippy::redundant_clone)]
let mut lowpassed_f64 = samples_h_orig.clone();
lowpass_filter(lowpassed_f32.as_mut_slice(), 44100.0, 90.0);
lowpass_filter_f64(lowpassed_f64.as_mut_slice(), 44100.0, 90.0);
let power_f32 =
calculate_power(&lowpassed_f32.iter().map(|x| *x as f64).collect::<Vec<_>>());
let power_f64 = calculate_power(&lowpassed_f64);
assert!((power_f32 as f64 - power_f64).abs() <= 0.00024);
}
#[ignore]
#[test]
fn test_lowpass_filter_vs_biquad() {
let samples_orig = sine_wave_samples(350.0, 44100.0);
let mut samples = samples_orig.clone();
let now = Instant::now();
for _ in 0..1000 {
lowpass_filter_f64(samples.as_mut_slice(), 44100.0, 90.0);
}
let duration_lowpass_filter = now.elapsed().as_secs_f64() / 1000.0;
let duration_biquad = {
let f0 = 80.hz();
let fs = 44.1.khz();
let coeffs =
Coefficients::<f64>::from_params(Type::LowPass, fs, f0, Q_BUTTERWORTH_F64).unwrap();
let mut lowpassed_data = Vec::with_capacity(samples_orig.len());
let mut biquad_lpf = DirectForm1::<f64>::new(coeffs);
let now = Instant::now();
for _ in 0..1000 {
samples_orig
.iter()
.for_each(|val| lowpassed_data.push(biquad_lpf.run(*val)));
}
now.elapsed().as_secs_f64() / 1000.0
};
println!(
"lowpass filter on average: {}µs",
duration_lowpass_filter * 1_000_000.0
);
println!(
"biquad filter on average : {}µs",
duration_biquad * 1_000_000.0
);
}
}