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use alloc::sync::Arc;
use core::sync::atomic::{AtomicU32, Ordering};
use crate::{frame, math::Float, Frame, Seek, Signal, Smoothed};
/// Amplifies a signal by a constant amount
///
/// Unlike [`Gain`], this can implement [`Seek`].
pub struct FixedGain<T: ?Sized> {
gain: f32,
inner: T,
}
impl<T> FixedGain<T> {
/// Amplify `signal` by `db` decibels
///
/// Decibels are perceptually linear. Negative values make the signal quieter.
pub fn new(signal: T, db: f32) -> Self {
Self {
gain: 10.0f32.powf(db / 20.0),
inner: signal,
}
}
}
impl<T: Signal + ?Sized> Signal for FixedGain<T>
where
T::Frame: Frame,
{
type Frame = T::Frame;
fn sample(&mut self, interval: f32, out: &mut [T::Frame]) {
self.inner.sample(interval, out);
for x in out {
*x = frame::scale(x, self.gain);
}
}
fn is_finished(&self) -> bool {
self.inner.is_finished()
}
}
impl<T: Seek + ?Sized> Seek for FixedGain<T>
where
T::Frame: Frame,
{
fn seek(&mut self, seconds: f32) {
self.inner.seek(seconds)
}
}
/// Amplifies a signal dynamically
///
/// To implement a volume control, place a gain combinator near the end of your pipeline where the
/// input amplitude is initially in the range [0, 1] and pass decibels to [`GainControl::set_gain`],
/// mapping the maximum volume to 0 decibels, and the minimum to e.g. -60.
pub struct Gain<T: ?Sized> {
shared: Arc<AtomicU32>,
gain: Smoothed<f32>,
inner: T,
}
impl<T> Gain<T> {
/// Apply dynamic amplification to `signal`
pub fn new(signal: T) -> (GainControl, Self) {
let signal = Gain {
shared: Arc::new(AtomicU32::new(1.0f32.to_bits())),
gain: Smoothed::new(1.0),
inner: signal,
};
let handle = GainControl(signal.shared.clone());
(handle, signal)
}
/// Set the initial amplification to `db` decibels
///
/// Perceptually linear. Negative values make the signal quieter.
///
/// Equivalent to `self.set_amplitude_ratio(10.0f32.powf(db / 20.0))`.
pub fn set_gain(&mut self, db: f32) {
self.set_amplitude_ratio(10.0f32.powf(db / 20.0));
}
/// Set the initial amplitude scaling of the signal directly
///
/// This is nonlinear in terms of both perception and power. Most users should prefer
/// `set_gain`. Unlike `set_gain`, this method allows a signal to be completely zeroed out if
/// needed, or even have its phase inverted with a negative factor.
pub fn set_amplitude_ratio(&mut self, factor: f32) {
self.shared.store(factor.to_bits(), Ordering::Relaxed);
self.gain = Smoothed::new(factor);
}
}
impl<T: Signal> Signal for Gain<T>
where
T::Frame: Frame,
{
type Frame = T::Frame;
#[allow(clippy::float_cmp)]
fn sample(&mut self, interval: f32, out: &mut [T::Frame]) {
self.inner.sample(interval, out);
let shared = f32::from_bits(self.shared.load(Ordering::Relaxed));
if self.gain.target() != &shared {
self.gain.set(shared);
}
if self.gain.progress() == 1.0 {
let g = self.gain.get();
if g != 1.0 {
for x in out {
*x = frame::scale(x, g);
}
}
return;
}
for x in out {
*x = frame::scale(x, self.gain.get());
self.gain.advance(interval / SMOOTHING_PERIOD);
}
}
fn is_finished(&self) -> bool {
self.inner.is_finished()
}
}
/// Thread-safe control for a [`Gain`] filter
pub struct GainControl(Arc<AtomicU32>);
impl GainControl {
/// Get the current amplification in decibels
pub fn gain(&self) -> f32 {
20.0 * self.amplitude_ratio().log10()
}
/// Amplify the signal by `db` decibels
///
/// Perceptually linear. Negative values make the signal quieter.
///
/// Equivalent to `self.set_amplitude_ratio(10.0f32.powf(db / 20.0))`.
pub fn set_gain(&mut self, db: f32) {
self.set_amplitude_ratio(10.0f32.powf(db / 20.0));
}
/// Get the current amplitude scaling factor
pub fn amplitude_ratio(&self) -> f32 {
f32::from_bits(self.0.load(Ordering::Relaxed))
}
/// Scale the amplitude of the signal directly
///
/// This is nonlinear in terms of both perception and power. Most users should prefer
/// `set_gain`. Unlike `set_gain`, this method allows a signal to be completely zeroed out if
/// needed, or even have its phase inverted with a negative factor.
pub fn set_amplitude_ratio(&mut self, factor: f32) {
self.0.store(factor.to_bits(), Ordering::Relaxed);
}
}
/// Number of seconds over which to smooth a change in gain
const SMOOTHING_PERIOD: f32 = 0.1;
#[cfg(test)]
mod tests {
use super::*;
use crate::Constant;
#[test]
fn smoothing() {
let (mut c, mut s) = Gain::new(Constant(1.0));
let mut buf = [0.0; 6];
c.set_amplitude_ratio(5.0);
s.sample(0.025, &mut buf);
assert_eq!(buf, [1.0, 2.0, 3.0, 4.0, 5.0, 5.0]);
s.sample(0.025, &mut buf);
assert_eq!(buf, [5.0; 6]);
}
}