X-Git-Url: https://git.nihav.org/?a=blobdiff_plain;f=nihav-core%2Fsrc%2Fdsp%2Fwindow.rs;fp=nihav-core%2Fsrc%2Fdsp%2Fwindow.rs;h=42b6b6d1d556f4918006b15ac51428fd26c2a102;hb=5641dccfbf2a70d589cf094a0d4ed5a10f919f00;hp=0000000000000000000000000000000000000000;hpb=b74ff9fac35d41737d71d97227fad233aa4a4b49;p=nihav.git

diff --git a/nihav-core/src/dsp/window.rs b/nihav-core/src/dsp/window.rs
new file mode 100644
index 0000000..42b6b6d
--- /dev/null
+++ b/nihav-core/src/dsp/window.rs
@@ -0,0 +1,52 @@
+use std::f32::consts;
+
+#[derive(Debug,Clone,Copy,PartialEq)]
+pub enum WindowType {
+    Square,
+    Sine,
+    KaiserBessel(f32),
+}
+
+pub fn generate_window(mode: WindowType, scale: f32, size: usize, half: bool, dst: &mut [f32]) {
+    match mode {
+        WindowType::Square => {
+                for n in 0..size { dst[n] = scale; }
+            },
+        WindowType::Sine => {
+                let param;
+                if half {
+                    param = consts::PI / ((2 * size) as f32);
+                } else {
+                    param = consts::PI / (size as f32);
+                }
+                for n in 0..size {
+                    dst[n] = (((n as f32) + 0.5) * param).sin() * scale;
+                }
+            },
+        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
+}