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Add a fadeout start to Safety Limiter

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This commit is contained in:
Robbert van der Helm 2022-05-25 00:59:46 +02:00
parent 3e5393b236
commit 9ab5af0027
1 changed files with 28 additions and 14 deletions
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42
plugins/safety_limiter/src/lib.rs
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@ -17,9 +17,13 @@
use nih_plug::prelude::*; use nih_plug::prelude::*;
use std::sync::Arc; use std::sync::Arc;
/// After reaching the threshold, it will take this many milliseconds under that threshold to fade /// After reaching the threshold, it will take this many milliseconds under that threshold to start
/// back to the normal signal. Peaking above the threshold again during this time resets this. /// fading back to the normal signal. Peaking above the threshold again during this time resets
const MORSE_FADEOUT_MS: f32 = 2000.0; /// this. The fadeout doesn't start immediately since that would add some nasty distortion when most
/// but not all samples pass the threshold.
const MORSE_FADEOUT_START_MS: f32 = 500.0;
/// The Morse fadeout ends after this many milliseconds.
const MORSE_FADEOUT_END_MS: f32 = MORSE_FADEOUT_START_MS + 1500.0;
/// The frequency of the sine wave used for the SOS signal. /// The frequency of the sine wave used for the SOS signal.
const MORSE_FREQUENCY: f32 = 420.0; const MORSE_FREQUENCY: f32 = 420.0;
@ -28,8 +32,10 @@ struct SafetyLimiter {
buffer_config: BufferConfig, buffer_config: BufferConfig,
/// `MORSE_FADEOUT_MS` translated into samples. /// `MORSE_FADEOUT_START_MS` translated into samples.
morse_fadeout_samples_total: u32, morse_fadeout_samples_start: u32,
/// `MORSE_FADEOUT_END_MS` translated into samples.
morse_fadeout_samples_end: u32,
/// The number of samples into the fadeout. /// The number of samples into the fadeout.
morse_fadeout_samples_current: u32, morse_fadeout_samples_current: u32,
@ -80,7 +86,8 @@ impl Default for SafetyLimiter {
process_mode: ProcessMode::Realtime, process_mode: ProcessMode::Realtime,
}, },
morse_fadeout_samples_total: 0, morse_fadeout_samples_start: 0,
morse_fadeout_samples_end: 0,
morse_fadeout_samples_current: 0, morse_fadeout_samples_current: 0,
osc_phase_tau: 0.0, osc_phase_tau: 0.0,
@ -115,15 +122,17 @@ impl Plugin for SafetyLimiter {
_context: &mut impl ProcessContext, _context: &mut impl ProcessContext,
) -> bool { ) -> bool {
self.buffer_config = *buffer_config; self.buffer_config = *buffer_config;
self.morse_fadeout_samples_total = self.morse_fadeout_samples_start =
(MORSE_FADEOUT_MS / 1000.0 * buffer_config.sample_rate).round() as u32; (MORSE_FADEOUT_START_MS / 1000.0 * buffer_config.sample_rate).round() as u32;
self.morse_fadeout_samples_end =
(MORSE_FADEOUT_END_MS / 1000.0 * buffer_config.sample_rate).round() as u32;
self.osc_phase_tau_dt = MORSE_FREQUENCY / buffer_config.sample_rate * std::f32::consts::TAU; self.osc_phase_tau_dt = MORSE_FREQUENCY / buffer_config.sample_rate * std::f32::consts::TAU;
true true
} }
fn reset(&mut self) { fn reset(&mut self) {
self.morse_fadeout_samples_current = self.morse_fadeout_samples_total; self.morse_fadeout_samples_current = self.morse_fadeout_samples_end;
self.reset_morse_signal(); self.reset_morse_signal();
} }
@ -147,7 +156,7 @@ impl Plugin for SafetyLimiter {
if is_peaking { if is_peaking {
// We'll continue playback where it was left off when this gets triggered before the // We'll continue playback where it was left off when this gets triggered before the
// fadeout has finished, but otherwise the sequence should be restarted. // fadeout has finished, but otherwise the sequence should be restarted.
if self.morse_fadeout_samples_current >= self.morse_fadeout_samples_total { if self.morse_fadeout_samples_current >= self.morse_fadeout_samples_end {
self.reset_morse_signal(); self.reset_morse_signal();
} }
@ -155,7 +164,7 @@ impl Plugin for SafetyLimiter {
self.morse_fadeout_samples_current = 0; self.morse_fadeout_samples_current = 0;
} }
if self.morse_fadeout_samples_current < self.morse_fadeout_samples_total { if self.morse_fadeout_samples_current < self.morse_fadeout_samples_end {
// This phase runs from 0 to `2 * pi` as an optimization, so we can use it directly. // This phase runs from 0 to `2 * pi` as an optimization, so we can use it directly.
// And the sine wave is scaled down to the threshold minus 12 dB // And the sine wave is scaled down to the threshold minus 12 dB
let sine_wave = let sine_wave =
@ -165,9 +174,14 @@ impl Plugin for SafetyLimiter {
self.osc_phase_tau -= std::f32::consts::TAU; self.osc_phase_tau -= std::f32::consts::TAU;
} }
let original_t = (self.morse_fadeout_samples_current as f32 let original_t = if self.morse_fadeout_samples_current
/ self.morse_fadeout_samples_total as f32) < self.morse_fadeout_samples_start
.cbrt(); {
0.0
} else {
(self.morse_fadeout_samples_current - self.morse_fadeout_samples_start) as f32
/ (self.morse_fadeout_samples_end - self.morse_fadeout_samples_start) as f32
};
let morse_t = 1.0 - original_t; let morse_t = 1.0 - original_t;
for sample in channel_samples { for sample in channel_samples {
*sample = (sine_wave * morse_t) + (*sample * original_t); *sample = (sine_wave * morse_t) + (*sample * original_t);