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vp6: switch to MD5-based tests
[nihav.git] / nihav-core / src / dsp / window.rs
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1use std::f32::consts;
2
3#[derive(Debug,Clone,Copy,PartialEq)]
4pub enum WindowType {
5 Square,
6 Sine,
9669f269 7 KaiserBessel(f32),
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8}
9
10pub fn generate_window(mode: WindowType, scale: f32, size: usize, half: bool, dst: &mut [f32]) {
11 match mode {
12 WindowType::Square => {
13 for n in 0..size { dst[n] = scale; }
14 },
15 WindowType::Sine => {
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16 let param = if half {
17 consts::PI / ((2 * size) as f32)
18 } else {
19 consts::PI / (size as f32)
20 };
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21 for n in 0..size {
22 dst[n] = (((n as f32) + 0.5) * param).sin() * scale;
23 }
24 },
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25 WindowType::KaiserBessel(alpha) => {
26 let dlen = if half { size as f32 } else { (size as f32) * 0.5 };
fdb4b2fb 27 let alpha2 = f64::from((alpha * consts::PI / dlen) * (alpha * consts::PI / dlen));
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28
29 let mut kb: Vec<f64> = Vec::with_capacity(size);
30 let mut sum = 0.0;
31 for n in 0..size {
32 let b = bessel_i0(((n * (size - n)) as f64) * alpha2);
33 sum += b;
34 kb.push(sum);
35 }
36 sum += 1.0;
37 for n in 0..size {
38 dst[n] = (kb[n] / sum).sqrt() as f32;
39 }
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40 },
41 };
42}
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43
44fn bessel_i0(inval: f64) -> f64 {
45 let mut val: f64 = 1.0;
46 for n in (1..64).rev() {
fdb4b2fb 47 val *= inval / f64::from(n * n);
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48 val += 1.0;
49 }
50 val
51}