1 files changed, 49 insertions, 0 deletions
diff --git a/mumd/src/audio/transformers.rs b/mumd/src/audio/transformers.rs
new file mode 100644
index 0000000..25e28b8
--- /dev/null
+++ b/mumd/src/audio/transformers.rs
@@ -0,0 +1,49 @@
+/// A trait that represents a transform of a audio buffer in some way.
+pub trait Transformer {
+    /// Do the transform. Returning `None` is interpreted as "the buffer is unwanted".
+    /// The implementor is free to modify the buffer however it wants to.
+    fn transform<'a>(&mut self, buf: &'a mut [f32]) -> Option<&'a mut [f32]>;
+}
+
+/// A struct representing a noise gate transform.
+pub struct NoiseGate {
+    alltime_high: f32,
+    open: usize,
+    deactivation_delay: usize,
+}
+
+impl NoiseGate {
+    /// Create a new noise gate. `deactivation_delay` is defined in terms of
+    /// how many quiet frames it receives before closing the noise gate.
+    pub fn new(deactivation_delay: usize) -> Self {
+        Self {
+            alltime_high: 0.0,
+            open: 0,
+            deactivation_delay,
+        }
+    }
+}
+
+impl Transformer for NoiseGate {
+    fn transform<'a>(&mut self, buf: &'a mut [f32]) -> Option<&'a mut [f32]> {
+        const MUTE_PERCENTAGE: f32 = 0.1;
+
+        let max = buf.iter().map(|e| e.abs()).max_by(|a, b| a.partial_cmp(b).unwrap()).unwrap();
+
+        if max > self.alltime_high {
+            self.alltime_high = max;
+        }
+
+        if max > self.alltime_high * MUTE_PERCENTAGE {
+            self.open = self.deactivation_delay;
+        } else if self.open > 0 {
+            self.open -= 1;
+        }
+
+        if self.open == 0 {
+            None
+        } else {
+            Some(buf)
+        }
+    }
+}