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Add a noise low-pass filter for Crisp

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This commit is contained in:
Robbert van der Helm 2022-03-09 18:25:27 +01:00
parent cdad01063e
commit 9bb46fc377
1 changed files with 65 additions and 3 deletions
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68
plugins/crisp/src/lib.rs
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@ -53,11 +53,11 @@ struct Crisp {
/// Resonant filters for low passing the input signal before RM'ing, to allow this to work with
/// inputs that already contain a lot of high freuqency content.
rm_input_lpf: [filter::Biquad<f32>; NUM_CHANNELS as usize],
/// Resonant filters for high passing the noise signal, to make it even brighter.
/// Resonant filters for high- and then low- passing the noise signal, to make it even brighter.
noise_hpf: [filter::Biquad<f32>; NUM_CHANNELS as usize],
noise_lpf: [filter::Biquad<f32>; NUM_CHANNELS as usize],
}
// TODO: Add more kinds of noise
#[derive(Params)]
pub struct CrispParams {
/// On a range of `[0, 1]`, how much of the modulated sound to mix in.
@ -83,6 +83,12 @@ pub struct CrispParams {
/// The Q parameter for the high pass-filter applied to the noise.
#[id = "nzhpfq"]
noise_hpf_q: FloatParam,
/// The cutoff frequency for the low-pass filter applied to the noise.
#[id = "nzlpff"]
noise_lpf_freq: FloatParam,
/// The Q parameter for the low pass-filter applied to the noise.
#[id = "nzlpfq"]
noise_lpf_q: FloatParam,
/// Output gain, as voltage gain. Displayed in decibels.
#[id = "output"]
@ -122,6 +128,7 @@ impl Default for Crisp {
prng: INITIAL_PRNG_SEED,
rm_input_lpf: [filter::Biquad::default(); NUM_CHANNELS as usize],
noise_hpf: [filter::Biquad::default(); NUM_CHANNELS as usize],
noise_lpf: [filter::Biquad::default(); NUM_CHANNELS as usize],
}
}
}
@ -211,6 +218,42 @@ impl Default for CrispParams {
)
.with_smoother(SmoothingStyle::Logarithmic(100.0))
.with_value_to_string(formatters::f32_rounded(2)),
noise_lpf_freq: FloatParam::new(
"Noise LP Frequency",
22_000.0,
FloatRange::Skewed {
min: 5.0,
max: 22_000.0,
factor: FloatRange::skew_factor(-1.0),
},
)
.with_smoother(SmoothingStyle::Logarithmic(100.0))
// The unit is baked into the value so we can show the disabled string
.with_value_to_string(Arc::new(|value| {
if value >= 22_000.0 {
String::from("Disabled")
} else {
format!("{:.0} Hz", value)
}
}))
.with_string_to_value(Arc::new(|string| {
if string == "Disabled" {
Some(22_000.0)
} else {
string.trim().trim_end_matches(" Hz").parse().ok()
}
})),
noise_lpf_q: FloatParam::new(
"Noise LP Resonance",
2.0f32.sqrt() / 2.0,
FloatRange::Skewed {
min: 2.0f32.sqrt() / 2.0,
max: 10.0,
factor: FloatRange::skew_factor(-1.0),
},
)
.with_smoother(SmoothingStyle::Logarithmic(100.0))
.with_value_to_string(formatters::f32_rounded(2)),
output_gain: FloatParam::new(
"Output",
@ -284,6 +327,9 @@ impl Plugin for Crisp {
for filter in &mut self.noise_hpf {
filter.reset();
}
for filter in &mut self.noise_lpf {
filter.reset();
}
}
fn process(
@ -327,7 +373,8 @@ impl Crisp {
/// Generate a new noise sample with the high pass filter applied.
fn gen_noise(&mut self, channel: usize) -> f32 {
let noise = self.prng.next_f32() * 2.0 - 1.0;
self.noise_hpf[channel].process(noise)
let high_passed = self.noise_hpf[channel].process(noise);
self.noise_lpf[channel].process(high_passed)
}
/// Perform the RM step depending on the mode. This applies a low pass filter to the input
@ -355,6 +402,11 @@ impl Crisp {
{
self.update_noise_hpf();
}
if self.params.noise_lpf_freq.smoothed.is_smoothing()
|| self.params.noise_lpf_q.smoothed.is_smoothing()
{
self.update_noise_lpf();
}
}
/// Update the filter coefficients if needed. Should be called explicitly from `initialize()`.
@ -376,6 +428,16 @@ impl Crisp {
filter.coefficients = coefficients;
}
}
/// Update the filter coefficients if needed. Should be called explicitly from `initialize()`.
fn update_noise_lpf(&mut self) {
let frequency = self.params.noise_lpf_freq.smoothed.next();
let q = self.params.noise_lpf_q.smoothed.next();
let coefficients = filter::BiquadCoefficients::lowpass(self.sample_rate, frequency, q);
for filter in &mut self.noise_lpf {
filter.coefficients = coefficients;
}
}
}
impl ClapPlugin for Crisp {