diff --git a/plugins/safety_limiter/src/lib.rs b/plugins/safety_limiter/src/lib.rs index 29ae9192..fc4d9d4c 100644 --- a/plugins/safety_limiter/src/lib.rs +++ b/plugins/safety_limiter/src/lib.rs @@ -27,6 +27,43 @@ const MORSE_FADEOUT_END_MS: f32 = MORSE_FADEOUT_START_MS + 1500.0; /// The frequency of the sine wave used for the SOS signal. const MORSE_FREQUENCY: f32 = 420.0; +/// The four second SOS morse code sequence. Each element here represents an edge where the signal +/// is either turned on or off. The first element of each tuple is the time in milliseconds into the +/// sequence, while the second element is the new gate status at that time point. The last element +/// acts as a delay before wrapping around, and it is equivalent to the 0 position in the next cycle +/// (hence why it is set to true). +const MORSE_SEQ_EDGES_MS: [(u32, bool); 19] = [ + // S, 3*100 ms + 2*100ms spacing + (0, true), + (100, false), + (200, true), + (300, false), + (400, true), + // 500 ms silence + (500, false), + // + // O, 3*200 ms + 2*100ms spacing + (1000, true), + (1200, false), + (1400, true), + (1600, false), + (1800, true), + // 500 ms silence + (2000, false), + // + // S, 3*100 ms + 2*100ms spacing + (2500, true), + (2600, false), + (2700, true), + (2800, false), + (2900, true), + // 1000 ms silence + (3000, false), + // Acts as a delay at the end before the sequence loops. This sample 4000 behaves like an alias + // for sample 0 in the next cycle. + (4000, true), +]; + struct SafetyLimiter { params: Arc, @@ -36,8 +73,18 @@ struct SafetyLimiter { morse_fadeout_samples_start: u32, /// `MORSE_FADEOUT_END_MS` translated into samples. morse_fadeout_samples_end: u32, - /// The number of samples into the fadeout. + /// `MORSE_SEQ_EDGES_MS` translated into samples. + morse_seq_edges_samples: [(u32, bool); 19], + + /// The number of samples into the fadeout. This resets back to 0 whenever the signal peaks + /// above the threshold. morse_fadeout_samples_current: u32, + /// The index of the current step into `morse_seq_edges_samples`. This wraps around to zero when + /// reaching the end of the sequence. This is only reset once the fadeout is fully finished. + morse_seq_current_step_idx: usize, + /// The index of the current sample in the morse code qeuence. This wraps around to zero when + /// reaching the end of the sequence. This is only reset once the fadeout is fully finished. + morse_seq_current_sample_idx: u32, /// The phase of the Morse code sine oscillator. This runs from zero to `2 * pi` for /// efficiency's sake. @@ -88,7 +135,11 @@ impl Default for SafetyLimiter { morse_fadeout_samples_start: 0, morse_fadeout_samples_end: 0, + morse_seq_edges_samples: [(0, false); 19], + morse_fadeout_samples_current: 0, + morse_seq_current_sample_idx: 0, + morse_seq_current_step_idx: 0, osc_phase_tau: 0.0, osc_phase_tau_dt: 0.0, @@ -128,6 +179,13 @@ impl Plugin for SafetyLimiter { (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.morse_seq_edges_samples = MORSE_SEQ_EDGES_MS.map(|(time_ms, gate)| { + ( + (time_ms as f32 / 1000.0 * buffer_config.sample_rate).round() as u32, + gate, + ) + }); + true } @@ -146,13 +204,13 @@ impl Plugin for SafetyLimiter { return ProcessStatus::Normal; } + let &(morse_seq_len, _) = self.morse_seq_edges_samples.last().unwrap(); for mut channel_samples in buffer.iter_samples() { let mut is_peaking = false; for sample in channel_samples.iter_mut() { is_peaking |= sample.abs() > self.params.threshold_gain.value; } - // TODO: Do the morse code thing, right now this just fades to silence if is_peaking { // 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. @@ -164,16 +222,41 @@ impl Plugin for SafetyLimiter { self.morse_fadeout_samples_current = 0; } + // Depending on the current gate status in the morse code sequence we'll either play a + // sine wave oscillator or silence, and the original audio will be faded back in when it + // stays under the threshold for long enough. 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. - // And the sine wave is scaled down to the threshold minus 12 dB - let sine_wave = - self.osc_phase_tau.sin() * (self.params.threshold_gain.value * 0.25); - self.osc_phase_tau += self.osc_phase_tau_dt; - if self.osc_phase_tau >= std::f32::consts::TAU { - self.osc_phase_tau -= std::f32::consts::TAU; + // Move to the next step when it is reached + // NOTE: This assumes there are no two edges at the same time, becuase that would be + // weird + // NOTE: Also assumes the sequence starts at 0 + let morse_seq_next_step_idx = + (self.morse_seq_current_step_idx + 1) % self.morse_seq_edges_samples.len(); + if self.morse_seq_current_sample_idx + >= self.morse_seq_edges_samples[morse_seq_next_step_idx].0 + { + self.morse_seq_current_step_idx = morse_seq_next_step_idx; } + // And either play or don't play the sine wave depending on the current step's gate + // values. We'll wait for the phase wraparound when deactivating the sine wave to + // avoid clicks. + let (_, gate) = self.morse_seq_edges_samples[self.morse_seq_current_step_idx]; + let morse_sample = if gate || self.osc_phase_tau > self.osc_phase_tau_dt { + // 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 24 dB + let sine_sample = + self.osc_phase_tau.sin() * (self.params.threshold_gain.value * 0.125); + self.osc_phase_tau += self.osc_phase_tau_dt; + if self.osc_phase_tau >= std::f32::consts::TAU { + self.osc_phase_tau -= std::f32::consts::TAU; + } + + sine_sample + } else { + 0.0 + }; + // We'll do an equal power fade let original_t_squared = if self.morse_fadeout_samples_current < self.morse_fadeout_samples_start @@ -186,10 +269,15 @@ impl Plugin for SafetyLimiter { let original_t = original_t_squared.sqrt(); let morse_t = (1.0 - original_t_squared).sqrt(); for sample in channel_samples { - *sample = (sine_wave * morse_t) + (*sample * original_t); + *sample = (morse_sample * morse_t) + (*sample * original_t); } self.morse_fadeout_samples_current += 1; + self.morse_seq_current_sample_idx += 1; + if self.morse_seq_current_sample_idx >= morse_seq_len { + self.morse_seq_current_sample_idx -= morse_seq_len; + self.morse_seq_current_step_idx = 0; + } } } @@ -201,6 +289,8 @@ impl SafetyLimiter { /// Reset the SOS signal to the start. fn reset_morse_signal(&mut self) { self.osc_phase_tau = 0.0; + self.morse_seq_current_step_idx = 0; + self.morse_seq_current_sample_idx = 0; } }