108 lines
3.4 KiB
Rust
108 lines
3.4 KiB
Rust
//! Miscellaneous feature extraction module.
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//!
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//! Contains various descriptors that don't fit in one of the
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//! existing categories.
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use bliss_audio_aubio_rs::level_lin;
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use ndarray::{arr1, Axis};
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use super::utils::{mean, Normalize};
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/**
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* Loudness (in dB) detection object.
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*
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* It indicates how "loud" a recording of a song is. For a given audio signal,
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* this value increases if the amplitude of the signal, and nothing else, is
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* increased.
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*
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* Of course, this makes this result dependent of the recording, meaning
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* the same song would yield different loudness on different recordings. Which
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* is exactly what we want, given that this is not a music theory project, but
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* one that aims at giving the best real-life results.
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*
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* Ranges between -90 dB (~silence) and 0 dB.
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*
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* (This is technically the sound pressure level of the track, but loudness is
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* way more visual)
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*/
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#[derive(Default)]
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pub(crate) struct LoudnessDesc {
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pub values: Vec<f32>,
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}
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impl LoudnessDesc {
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pub const WINDOW_SIZE: usize = 1024;
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pub fn do_(&mut self, chunk: &[f32]) {
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let level = level_lin(chunk);
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self.values.push(level);
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}
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pub fn get_value(&mut self) -> Vec<f32> {
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let mut std_value = arr1(&self.values).std_axis(Axis(0), 0.).into_scalar();
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let mut mean_value = mean(&self.values);
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// Make sure the dB don't go less than -90dB
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if mean_value < 1e-9 {
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mean_value = 1e-9
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};
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if std_value < 1e-9 {
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std_value = 1e-9
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}
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vec![
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self.normalize(10.0 * mean_value.log10()),
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self.normalize(10.0 * std_value.log10()),
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]
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}
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}
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impl Normalize for LoudnessDesc {
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const MAX_VALUE: f32 = 0.;
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const MIN_VALUE: f32 = -90.;
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use crate::Song;
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use std::path::Path;
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#[test]
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fn test_loudness() {
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let song = Song::decode(Path::new("data/s16_mono_22_5kHz.flac")).unwrap();
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let mut loudness_desc = LoudnessDesc::default();
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for chunk in song.sample_array.chunks_exact(LoudnessDesc::WINDOW_SIZE) {
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loudness_desc.do_(&chunk);
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}
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let expected_values = vec![0.271263, 0.2577181];
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for (expected, actual) in expected_values.iter().zip(loudness_desc.get_value().iter()) {
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assert!(0.01 > (expected - actual).abs());
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}
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}
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#[test]
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fn test_loudness_boundaries() {
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let mut loudness_desc = LoudnessDesc::default();
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let silence_chunk = vec![0.; 1024];
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loudness_desc.do_(&silence_chunk);
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let expected_values = vec![-1., -1.];
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for (expected, actual) in expected_values.iter().zip(loudness_desc.get_value().iter()) {
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assert!(0.0000001 > (expected - actual).abs());
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}
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let mut loudness_desc = LoudnessDesc::default();
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let silence_chunk = vec![1.; 1024];
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loudness_desc.do_(&silence_chunk);
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let expected_values = vec![1., -1.];
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for (expected, actual) in expected_values.iter().zip(loudness_desc.get_value().iter()) {
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assert!(0.0000001 > (expected - actual).abs());
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}
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let mut loudness_desc = LoudnessDesc::default();
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let silence_chunk = vec![-1.; 1024];
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loudness_desc.do_(&silence_chunk);
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let expected_values = vec![1., -1.];
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for (expected, actual) in expected_values.iter().zip(loudness_desc.get_value().iter()) {
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assert!(0.0000001 > (expected - actual).abs());
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}
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}
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}
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