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::{Axis, arr1};
8
9use crate::Feature;
10
11use super::utils::{Normalize, mean};
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) -> [Feature; 2] {
46        const MIN_VALUE: f32 = 1e-9;
47
48        // Make sure the dB don't go less than -90dB
49        let std_value = arr1(&self.values)
50            .std_axis(Axis(0), 0.)
51            .into_scalar()
52            .max(MIN_VALUE);
53        let mean_value = mean(&self.values).max(MIN_VALUE);
54        [
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::new()
75            .unwrap()
76            .decode(Path::new("data/s16_mono_22_5kHz.flac"))
77            .unwrap();
78        let mut loudness_desc = LoudnessDesc::default();
79        for chunk in song.samples.chunks_exact(LoudnessDesc::WINDOW_SIZE) {
80            loudness_desc.do_(chunk);
81        }
82        let expected_values = [0.271_263, 0.257_718_1];
83        for (expected, actual) in expected_values.iter().zip(loudness_desc.get_value().iter()) {
84            assert!(0.01 > (expected - actual).abs(), "{expected} !~= {actual}");
85        }
86    }
87
88    #[test]
89    fn test_loudness_boundaries() {
90        let mut loudness_desc = LoudnessDesc::default();
91        let silence_chunk = vec![0.; 1024];
92        loudness_desc.do_(&silence_chunk);
93        let expected_values = [-1., -1.];
94        for (expected, actual) in expected_values.iter().zip(loudness_desc.get_value().iter()) {
95            assert!(
96                0.000_000_1 > (expected - actual).abs(),
97                "{expected} !~= {actual}"
98            );
99        }
100
101        let mut loudness_desc = LoudnessDesc::default();
102        let silence_chunk = vec![1.; 1024];
103        loudness_desc.do_(&silence_chunk);
104        let expected_values = [1., -1.];
105        for (expected, actual) in expected_values.iter().zip(loudness_desc.get_value().iter()) {
106            assert!(
107                0.000_000_1 > (expected - actual).abs(),
108                "{expected} !~= {actual}"
109            );
110        }
111
112        let mut loudness_desc = LoudnessDesc::default();
113        let silence_chunk = vec![-1.; 1024];
114        loudness_desc.do_(&silence_chunk);
115        let expected_values = [1., -1.];
116        for (expected, actual) in expected_values.iter().zip(loudness_desc.get_value().iter()) {
117            assert!(
118                0.000_000_1 > (expected - actual).abs(),
119                "{expected} !~= {actual}"
120            );
121        }
122    }
123}
mecomp_analysis/misc.rs

mecomp_analysis/
misc.rs
