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    #[inline]
39    pub fn do_(&mut self, chunk: &[f32]) {
40        let level = level_lin(chunk);
41        self.values.push(level);
42    }
43
44    #[inline]
45    pub fn get_value(&mut self) -> Vec<Feature> {
46        // Make sure the dB don't go less than -90dB
47        let std_value = Feature::from(
48            arr1(&self.values)
49                .std_axis(Axis(0), 0.)
50                .into_scalar()
51                .max(1e-9),
52        );
53        let mean_value = Feature::from(mean(&self.values).max(1e-9));
54        vec![
55            self.normalize(10.0 * mean_value.log10()),
56            self.normalize(10.0 * std_value.log10()),
57        ]
58    }
59}
60
61impl Normalize for LoudnessDesc {
62    const MAX_VALUE: Feature = 0.;
63    const MIN_VALUE: Feature = -90.;
64}
65
66#[cfg(test)]
67mod tests {
68    use super::*;
69    use crate::decoder::{Decoder as DecoderTrait, MecompDecoder as Decoder};
70    use std::path::Path;
71
72    #[test]
73    fn test_loudness() {
74        let song = Decoder::decode(Path::new("data/s16_mono_22_5kHz.flac")).unwrap();
75        let mut loudness_desc = LoudnessDesc::default();
76        for chunk in song.samples.chunks_exact(LoudnessDesc::WINDOW_SIZE) {
77            loudness_desc.do_(chunk);
78        }
79        let expected_values = [0.271_263, 0.257_718_1];
80        for (expected, actual) in expected_values.iter().zip(loudness_desc.get_value().iter()) {
81            assert!(0.01 > (expected - actual).abs(), "{expected} !~= {actual}");
82        }
83    }
84
85    #[test]
86    fn test_loudness_boundaries() {
87        let mut loudness_desc = LoudnessDesc::default();
88        let silence_chunk = vec![0.; 1024];
89        loudness_desc.do_(&silence_chunk);
90        let expected_values = [-1., -1.];
91        for (expected, actual) in expected_values.iter().zip(loudness_desc.get_value().iter()) {
92            assert!(
93                0.000_000_1 > (expected - actual).abs(),
94                "{expected} !~= {actual}"
95            );
96        }
97
98        let mut loudness_desc = LoudnessDesc::default();
99        let silence_chunk = vec![1.; 1024];
100        loudness_desc.do_(&silence_chunk);
101        let expected_values = [1., -1.];
102        for (expected, actual) in expected_values.iter().zip(loudness_desc.get_value().iter()) {
103            assert!(
104                0.000_000_1 > (expected - actual).abs(),
105                "{expected} !~= {actual}"
106            );
107        }
108
109        let mut loudness_desc = LoudnessDesc::default();
110        let silence_chunk = vec![-1.; 1024];
111        loudness_desc.do_(&silence_chunk);
112        let expected_values = [1., -1.];
113        for (expected, actual) in expected_values.iter().zip(loudness_desc.get_value().iter()) {
114            assert!(
115                0.000_000_1 > (expected - actual).abs(),
116                "{expected} !~= {actual}"
117            );
118        }
119    }
120}
mecomp_analysis/misc.rs

mecomp_analysis/
misc.rs
