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dsp: implement Kaiser-Bessel derived window generation
author
Kostya Shishkov
<kostya.shishkov@gmail.com>
Sat, 27 Oct 2018 16:57:11 +0000
(18:57 +0200)
committer
Kostya Shishkov
<kostya.shishkov@gmail.com>
Sat, 27 Oct 2018 16:57:11 +0000
(18:57 +0200)
src/dsp/window.rs
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diff --git
a/src/dsp/window.rs
b/src/dsp/window.rs
index d59a005bbab26b0b449929d74e1ebda7236d6841..42b6b6d1d556f4918006b15ac51428fd26c2a102 100644
(file)
--- a/
src/dsp/window.rs
+++ b/
src/dsp/window.rs
@@
-4,7
+4,7
@@
use std::f32::consts;
pub enum WindowType {
Square,
Sine,
pub enum WindowType {
Square,
Sine,
- KaiserBessel,
+ KaiserBessel
(f32)
,
}
pub fn generate_window(mode: WindowType, scale: f32, size: usize, half: bool, dst: &mut [f32]) {
}
pub fn generate_window(mode: WindowType, scale: f32, size: usize, half: bool, dst: &mut [f32]) {
@@
-23,8
+23,30
@@
pub fn generate_window(mode: WindowType, scale: f32, size: usize, half: bool, ds
dst[n] = (((n as f32) + 0.5) * param).sin() * scale;
}
},
dst[n] = (((n as f32) + 0.5) * param).sin() * scale;
}
},
- WindowType::KaiserBessel => {
-unimplemented!();
+ WindowType::KaiserBessel(alpha) => {
+ let dlen = if half { size as f32 } else { (size as f32) * 0.5 };
+ let alpha2 = ((alpha * consts::PI / dlen) * (alpha * consts::PI / dlen)) as f64;
+
+ let mut kb: Vec<f64> = Vec::with_capacity(size);
+ let mut sum = 0.0;
+ for n in 0..size {
+ let b = bessel_i0(((n * (size - n)) as f64) * alpha2);
+ sum += b;
+ kb.push(sum);
+ }
+ sum += 1.0;
+ for n in 0..size {
+ dst[n] = (kb[n] / sum).sqrt() as f32;
+ }
},
};
}
},
};
}
+
+fn bessel_i0(inval: f64) -> f64 {
+ let mut val: f64 = 1.0;
+ for n in (1..64).rev() {
+ val *= inval / ((n * n) as f64);
+ val += 1.0;
+ }
+ val
+}