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/// 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.
#[derive(Debug)]
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)
}
}
}
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