dc block + lowpass

src/low_pass.rs

@@ -0,0 +1,39 @@
+use crate::fm_demod::Sample;
+
+pub struct LowPass<I> {
+    inner: I,
+    y_prev: Sample,
+    alpha: f32,
+}
+
+impl<I> LowPass<I> {
+    pub fn new(inner: I, alpha: f32) -> Self {
+        Self {
+            inner,
+            y_prev: 0.0,
+            alpha,
+        }
+    }
+
+    pub fn process_sample(&mut self, x_n: Sample) -> Sample {
+        let y_n = self.alpha * x_n + (1.0 - self.alpha) * self.y_prev;
+
+        self.y_prev = y_n;
+
+        y_n
+    }
+}
+
+impl<I, E> Iterator for LowPass<I>
+where
+    I: Iterator<Item = Result<Sample, E>>,
+{
+    type Item = Result<Sample, E>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match self.inner.next()? {
+            Ok(sample) => Some(Ok(self.process_sample(sample))),
+            Err(e) => Some(Err(e)),
+        }
+    }
+}