1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
use std::f64;
use crate::DctNum;
pub fn mp3<T: DctNum>(len: usize) -> Vec<T> {
let constant_term = f64::consts::PI / len as f64;
(0..len)
.map(|n| (constant_term * (n as f64 + 0.5f64)).sin())
.map(|w| T::from_f64(w).unwrap())
.collect()
}
pub fn mp3_invertible<T: DctNum>(len: usize) -> Vec<T> {
let outer_scale = (4.0 / len as f64).sqrt();
let constant_term = f64::consts::PI / len as f64;
(0..len)
.map(|n| (constant_term * (n as f64 + 0.5f64)).sin() * outer_scale)
.map(|w| T::from_f64(w).unwrap())
.collect()
}
pub fn vorbis<T: DctNum>(len: usize) -> Vec<T> {
let constant_term = f64::consts::PI / len as f64;
(0..len)
.map(|n| {
let inner_sin = (constant_term * (n as f64 + 0.5f64)).sin();
(f64::consts::PI * 0.5f64 * inner_sin * inner_sin).sin()
})
.map(|w| T::from_f64(w).unwrap())
.collect()
}
pub fn vorbis_invertible<T: DctNum>(len: usize) -> Vec<T> {
let outer_scale = (4.0 / len as f64).sqrt();
let constant_term = f64::consts::PI / len as f64;
(0..len)
.map(|n| {
let inner_sin = (constant_term * (n as f64 + 0.5f64)).sin();
(f64::consts::PI * 0.5f64 * inner_sin * inner_sin).sin() * outer_scale
})
.map(|w| T::from_f64(w).unwrap())
.collect()
}
pub fn one<T: DctNum>(len: usize) -> Vec<T> {
(0..len).map(|_| T::one()).collect()
}
pub fn invertible<T: DctNum>(len: usize) -> Vec<T> {
let constant_term = (2.0 / len as f64).sqrt();
(0..len)
.map(|_| constant_term)
.map(|w| T::from_f64(w).unwrap())
.collect()
}
#[cfg(test)]
mod unit_tests {
use super::*;
use crate::test_utils::fuzzy_cmp;
#[test]
fn test_window_fns() {
for test_fn in &[mp3, vorbis] {
for half_size in 1..20 {
let evaluated_window: Vec<f32> = test_fn(half_size * 2);
for i in 0..half_size {
let first = evaluated_window[i];
let second = evaluated_window[i + half_size];
assert!(fuzzy_cmp(first * first + second * second, 1f32, 0.001f32));
}
}
}
}
}