mecomp_analysis/
misc.rs

1//! Miscellaneous feature extraction module.
2//!
3//! Contains various descriptors that don't fit in one of the
4//! existing categories.
5
6use bliss_audio_aubio_rs::level_lin;
7use ndarray::{arr1, Axis};
8
9use crate::Feature;
10
11use super::utils::{mean, Normalize};
12
13/**
14 * Loudness (in dB) detection object.
15 *
16 * It indicates how "loud" a recording of a song is. For a given audio signal,
17 * this value increases if the amplitude of the signal, and nothing else, is
18 * increased.
19 *
20 * Of course, this makes this result dependent of the recording, meaning
21 * the same song would yield different loudness on different recordings. Which
22 * is exactly what we want, given that this is not a music theory project, but
23 * one that aims at giving the best real-life results.
24 *
25 * Ranges between -90 dB (~silence) and 0 dB.
26 *
27 * (This is technically the sound pressure level of the track, but loudness is
28 * way more visual)
29 */
30#[derive(Default, Clone)]
31pub struct LoudnessDesc {
32    pub values: Vec<f32>,
33}
34
35impl LoudnessDesc {
36    pub const WINDOW_SIZE: usize = 1024;
37
38    pub fn do_(&mut self, chunk: &[f32]) {
39        let level = level_lin(chunk);
40        self.values.push(level);
41    }
42
43    pub fn get_value(&mut self) -> Vec<Feature> {
44        // Make sure the dB don't go less than -90dB
45        let std_value = Feature::from(
46            arr1(&self.values)
47                .std_axis(Axis(0), 0.)
48                .into_scalar()
49                .max(1e-9),
50        );
51        let mean_value = Feature::from(mean(&self.values).max(1e-9));
52        vec![
53            self.normalize(10.0 * mean_value.log10()),
54            self.normalize(10.0 * std_value.log10()),
55        ]
56    }
57}
58
59impl Normalize for LoudnessDesc {
60    const MAX_VALUE: Feature = 0.;
61    const MIN_VALUE: Feature = -90.;
62}
63
64#[cfg(test)]
65mod tests {
66    use super::*;
67    use crate::decoder::{Decoder as DecoderTrait, MecompDecoder as Decoder};
68    use std::path::Path;
69
70    #[test]
71    fn test_loudness() {
72        let song = Decoder::decode(Path::new("data/s16_mono_22_5kHz.flac")).unwrap();
73        let mut loudness_desc = LoudnessDesc::default();
74        for chunk in song.samples.chunks_exact(LoudnessDesc::WINDOW_SIZE) {
75            loudness_desc.do_(chunk);
76        }
77        let expected_values = [0.271_263, 0.257_718_1];
78        for (expected, actual) in expected_values.iter().zip(loudness_desc.get_value().iter()) {
79            assert!(0.01 > (expected - actual).abs(), "{expected} !~= {actual}");
80        }
81    }
82
83    #[test]
84    fn test_loudness_boundaries() {
85        let mut loudness_desc = LoudnessDesc::default();
86        let silence_chunk = vec![0.; 1024];
87        loudness_desc.do_(&silence_chunk);
88        let expected_values = [-1., -1.];
89        for (expected, actual) in expected_values.iter().zip(loudness_desc.get_value().iter()) {
90            assert!(
91                0.000_000_1 > (expected - actual).abs(),
92                "{expected} !~= {actual}"
93            );
94        }
95
96        let mut loudness_desc = LoudnessDesc::default();
97        let silence_chunk = vec![1.; 1024];
98        loudness_desc.do_(&silence_chunk);
99        let expected_values = [1., -1.];
100        for (expected, actual) in expected_values.iter().zip(loudness_desc.get_value().iter()) {
101            assert!(
102                0.000_000_1 > (expected - actual).abs(),
103                "{expected} !~= {actual}"
104            );
105        }
106
107        let mut loudness_desc = LoudnessDesc::default();
108        let silence_chunk = vec![-1.; 1024];
109        loudness_desc.do_(&silence_chunk);
110        let expected_values = [1., -1.];
111        for (expected, actual) in expected_values.iter().zip(loudness_desc.get_value().iter()) {
112            assert!(
113                0.000_000_1 > (expected - actual).abs(),
114                "{expected} !~= {actual}"
115            );
116        }
117    }
118}
mecomp_analysis/misc.rs

mecomp_analysis/
misc.rs
