nih-plug/plugins/spectral_compressor/src/compressor_bank.rs

// Spectral Compressor: an FFT based compressor
// Copyright (C) 2021-2022 Robbert van der Helm
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::Arc;

use nih_plug::prelude::*;

/// A bank of compressors so each FFT bin can be compressed individually. The vectors in this struct
/// will have a capacity of `MAX_WINDOW_SIZE / 2 + 1` and a size that matches the current complex
/// FFT buffer size. This is stored as a struct of arrays to make SIMD-ing easier in the future.
pub struct CompressorBank {
    // TODO: The thresholds and ratios need to be split up in downwards and upwards variants
    /// If set, then the thresholds should be updated on the next processing cycle. Can be set from
    /// a parameter value change listener, and is also set when calling `.reset_for_size`.
    pub should_update_thresholds: Arc<AtomicBool>,
    /// If set, then the ratios should be updated on the next processing cycle. Can be set from a
    /// parameter value change listener, and is also set when calling `.reset_for_size`.
    pub should_update_ratios: Arc<AtomicBool>,

    /// Compressor thresholds, in linear space.
    thresholds: Vec<f32>,
    /// Compressor ratios. If [`CompressorBankParams::high_freq_ratio_rolloff`] is set to 1.0, then
    /// this will be the same for each compressor.
    ratios: Vec<f32>,
    /// The current envelope value for this bin, in linear space. Indexed by
    /// `[channel_idx][compressor_idx]`.
    envelopes: Vec<Vec<f32>>,
    // TODO: Parameters for the envelope followers so we can actuall ydo soemthing useful.
}

#[derive(Params)]
pub struct ThresholdParams {
    // TODO: Sidechaining
    /// The center frqeuency for the target curve when sidechaining is not enabled. The curve is a
    /// polynomial `threshold_db + curve_slope*x + curve_curve*(x^2)` that evaluates to a decibel
    /// value, where `x = log2(center_frequency) - log2(bin_frequency)`. In other words, this is
    /// evaluated in the log/log domain for decibels and octaves.
    #[id = "thresh_center_freq"]
    center_frequency: FloatParam,
    /// The compressor threshold at the center frequency. When sidechaining is enabled, the input
    /// signal is gained by the inverse of this value. This replaces the input gain in the original
    /// Spectral Compressor. In the polynomial above, this is the intercept.
    #[id = "input_db"]
    threshold_db: FloatParam,
    /// The slope for the curve, in the log/log domain. See the polynomial above.
    #[id = "thresh_curve_slope"]
    curve_slope: FloatParam,
    /// The, uh, 'curve' for the curve, in the logarithmic domain. This is the third coefficient in
    /// the quadratic polynomial and controls the parabolic behavior. Positive values turn the curve
    /// into a v-shaped curve, while negative values attenuate everything outside of the center
    /// frequency. See the polynomial above.
    #[id = "thresh_curve_curve"]
    curve_curve: FloatParam,
}

#[derive(Params)]
pub struct CompressorBankParams {
    // TODO: Target curve options
    /// The downwards compression threshold relative to the target curve.
    #[id = "thresh_down_off"]
    downwards_threshold_offset_db: FloatParam,
    /// The upwards compression threshold relative to the target curve.
    #[id = "thresh_up_off"]
    upwards_threshold_offset_db: FloatParam,

    /// A `[0, 1]` scaling factor that causes the compressors for the higher registers to have lower
    /// ratios than the compressors for the lower registers. The scaling is applied logarithmically
    /// rather than linearly over the compressors.
    ///
    /// TODO: Decide on whether or not this should only apply on upwards ratios, or if we may need
    ///       separate controls for both
    #[id = "ratio_hi_freq_rolloff"]
    high_freq_ratio_rolloff: FloatParam,
    /// The downwards compression ratio. At 1.0 the downwards compressor is disengaged.
    #[id = "ratio_down"]
    downwards_ratio: FloatParam,
    /// The upwards compression ratio. At 1.0 the upwards compressor is disengaged.
    #[id = "ratio_up"]
    upwards_ratio: FloatParam,

    /// The downwards compression knee width, in decibels.
    #[id = "knee_down_off"]
    downwards_knee_width_db: FloatParam,
    /// The upwards compression knee width, in decibels.
    #[id = "knee_up_off"]
    upwards_knee_width_db: FloatParam,

    /// The compressor's attack time in milliseconds. Controls both upwards and downwards
    /// compression.
    #[id = "attack"]
    compressor_attack_ms: FloatParam,
    /// The compressor's release time in milliseconds. Controls both upwards and downwards
    /// compression.
    #[id = "release"]
    compressor_release_ms: FloatParam,
}

impl ThresholdParams {
    /// Create a new [`ThresholdParams`] object. Changing any of the threshold parameters causes the
    /// passed compressor bank's thresholds to be updated.
    pub fn new(compressor_bank: &CompressorBank) -> Self {
        let should_update_thresholds = compressor_bank.should_update_thresholds.clone();
        let set_update_thresholds =
            Arc::new(move |_| should_update_thresholds.store(true, Ordering::SeqCst));

        ThresholdParams {
            center_frequency: FloatParam::new(
                "Threshold Center",
                500.0,
                FloatRange::Skewed {
                    min: 20.0,
                    max: 20_000.0,
                    factor: FloatRange::skew_factor(-2.0),
                },
            )
            .with_callback(set_update_thresholds.clone())
            // This includes the unit
            .with_value_to_string(formatters::v2s_f32_hz_then_khz(0))
            .with_string_to_value(formatters::s2v_f32_hz_then_khz()),
            // These are polynomial coefficients that are evaluated in the log/log domain
            // (octaves/decibels). The threshold is the intercept.
            threshold_db: FloatParam::new(
                "Global Threshold",
                0.0,
                FloatRange::Linear {
                    min: -50.0,
                    max: 50.0,
                },
            )
            .with_callback(set_update_thresholds.clone())
            .with_unit(" dB")
            .with_step_size(0.1),
            curve_slope: FloatParam::new(
                "Threshold Slope",
                0.0,
                FloatRange::Linear {
                    min: -24.0,
                    max: 24.0,
                },
            )
            .with_callback(set_update_thresholds.clone())
            .with_unit(" dB/oct")
            .with_step_size(0.1),
            curve_curve: FloatParam::new(
                "Threshold Curve",
                0.0,
                FloatRange::Linear {
                    min: -24.0,
                    max: 24.0,
                },
            )
            .with_callback(set_update_thresholds)
            .with_unit(" dB/oct²")
            .with_step_size(0.1),
        }
    }
}

impl CompressorBankParams {
    /// Create a new [`CompressorBankParams`] object. Changing any of the threshold or ratio
    /// parameters causes the passed compressor bank's parameters to be updated.
    pub fn new(compressor_bank: &CompressorBank) -> Self {
        let should_update_thresholds = compressor_bank.should_update_thresholds.clone();
        let set_update_thresholds =
            Arc::new(move |_| should_update_thresholds.store(true, Ordering::SeqCst));
        let should_update_ratios = compressor_bank.should_update_ratios.clone();
        let set_update_ratios =
            Arc::new(move |_| should_update_ratios.store(true, Ordering::SeqCst));

        CompressorBankParams {
            // TODO: Set nicer default values for these things
            // As explained above, these offsets are relative to the target curve
            downwards_threshold_offset_db: FloatParam::new(
                "Downwards Offset",
                0.0,
                FloatRange::Linear {
                    min: -50.0,
                    max: 50.0,
                },
            )
            .with_callback(set_update_thresholds.clone())
            .with_unit(" dB")
            .with_step_size(0.1),
            upwards_threshold_offset_db: FloatParam::new(
                "Upwards Offset",
                0.0,
                FloatRange::Linear {
                    min: -50.0,
                    max: 50.0,
                },
            )
            .with_callback(set_update_thresholds)
            .with_unit(" dB")
            .with_step_size(0.1),

            high_freq_ratio_rolloff: FloatParam::new(
                "High-freq Ratio Rolloff",
                0.5,
                FloatRange::Linear { min: 0.0, max: 1.0 },
            )
            .with_callback(set_update_ratios.clone())
            .with_unit("%")
            .with_value_to_string(formatters::v2s_f32_percentage(0))
            .with_string_to_value(formatters::s2v_f32_percentage()),
            downwards_ratio: FloatParam::new(
                "Downwards Ratio",
                1.0,
                FloatRange::Skewed {
                    min: 1.0,
                    max: 300.0,
                    factor: FloatRange::skew_factor(-2.0),
                },
            )
            .with_callback(set_update_ratios.clone())
            .with_step_size(0.1)
            .with_value_to_string(formatters::v2s_compression_ratio(1))
            .with_string_to_value(formatters::s2v_compression_ratio()),
            upwards_ratio: FloatParam::new(
                "Upwards Ratio",
                1.0,
                FloatRange::Skewed {
                    min: 1.0,
                    max: 300.0,
                    factor: FloatRange::skew_factor(-2.0),
                },
            )
            .with_callback(set_update_ratios)
            .with_step_size(0.1)
            .with_value_to_string(formatters::v2s_compression_ratio(1))
            .with_string_to_value(formatters::s2v_compression_ratio()),

            downwards_knee_width_db: FloatParam::new(
                "Downwards Knee",
                0.0,
                FloatRange::Skewed {
                    min: 0.0,
                    max: 36.0,
                    factor: FloatRange::skew_factor(-1.0),
                },
            )
            .with_unit(" dB")
            .with_step_size(0.1),
            upwards_knee_width_db: FloatParam::new(
                "Upwards Knee",
                0.0,
                FloatRange::Skewed {
                    min: 0.0,
                    max: 36.0,
                    factor: FloatRange::skew_factor(-1.0),
                },
            )
            .with_unit(" dB")
            .with_step_size(0.1),

            compressor_attack_ms: FloatParam::new(
                "Attack",
                150.0,
                FloatRange::Skewed {
                    // TODO: Make sure to handle 0 attack and release times in the compressor
                    min: 0.0,
                    max: 10_000.0,
                    factor: FloatRange::skew_factor(-2.0),
                },
            )
            .with_unit(" ms")
            .with_step_size(0.1),
            compressor_release_ms: FloatParam::new(
                "Release",
                300.0,
                FloatRange::Skewed {
                    min: 0.0,
                    max: 10_000.0,
                    factor: FloatRange::skew_factor(-2.0),
                },
            )
            .with_unit(" ms")
            .with_step_size(0.1),
        }
    }
}

impl CompressorBank {
    /// Set up the compressor for the given channel count and maximum FFT window size. The
    /// compressors won't be initialized yet.
    pub fn new(num_channels: usize, max_window_size: usize) -> Self {
        let complex_buffer_len = max_window_size / 2 + 1;

        CompressorBank {
            should_update_thresholds: Arc::new(AtomicBool::new(true)),
            should_update_ratios: Arc::new(AtomicBool::new(true)),

            thresholds: Vec::with_capacity(complex_buffer_len),
            ratios: Vec::with_capacity(complex_buffer_len),
            envelopes: vec![Vec::with_capacity(complex_buffer_len); num_channels],
        }
    }

    /// Change the capacities of the internal buffers to fit new parameters. Use the
    /// `.reset_for_size()` method to clear the buffers and set the current window size.
    pub fn update_capacity(&mut self, num_channels: usize, max_window_size: usize) {
        let complex_buffer_len = max_window_size / 2 + 1;

        self.thresholds
            .reserve_exact(complex_buffer_len.saturating_sub(self.thresholds.len()));
        self.ratios
            .reserve_exact(complex_buffer_len.saturating_sub(self.ratios.len()));
        self.envelopes.resize_with(num_channels, Vec::new);
        for envelopes in self.envelopes.iter_mut() {
            envelopes.reserve_exact(complex_buffer_len.saturating_sub(envelopes.len()));
        }
    }

    /// Resize the number of compressors to match the current window size.
    ///
    /// If the window size is larger than the maximum window size, then this will allocate.
    pub fn resize(&mut self, window_size: usize) {
        let complex_buffer_len = window_size / 2 + 1;

        self.thresholds.resize(complex_buffer_len, 1.0);
        self.ratios.resize(complex_buffer_len, 1.0);
        for envelopes in self.envelopes.iter_mut() {
            envelopes.resize(complex_buffer_len, 0.0);
        }

        // The compressors need to be updated on the next processing cycle
        self.should_update_thresholds.store(true, Ordering::SeqCst);
        self.should_update_ratios.store(true, Ordering::SeqCst);
    }

    /// Clear out the envelope followers.
    pub fn reset(&mut self) {
        for envelopes in self.envelopes.iter_mut() {
            envelopes.fill(0.0);
        }
    }

    /// Update the compressors if needed. This is called just before processing, and the compressors
    /// are updated in accordance to the atomic flags set on this struct.
    fn update_if_needed(&mut self) {
        //
    }
}