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Fix SC high freq rolloff at 22.05 kHz

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This prevents the effect from getting brighter as you increase the
sample rate.
This commit is contained in:
Robbert van der Helm 2022-09-14 17:46:28 +02:00
parent 374dfc9052
commit 5ac9c32c19
1 changed files with 9 additions and 9 deletions
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18
plugins/spectral_compressor/src/compressor_bank.rs
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@ -30,6 +30,10 @@ const UPWARDS_NAME_PREFIX: &str = "upwards_";
/// reactivating the plugin.
const ENVELOPE_INIT_VALUE: f32 = std::f32::consts::FRAC_1_SQRT_2 / 8.0;
/// The target frequency for the high frequency ratio rolloff. This is fixed to prevent Spectral
/// Compressor from getting brighter as the sample rate increases.
const HIGH_FREQ_RATIO_ROLLOFF_FREQUENCY: f32 = 22_050.0;
/// 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.
@ -170,7 +174,9 @@ pub struct CompressorParams {
/// 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. If this is set to 1.0, then the ratios will be
/// the same for every compressor.
/// the same for every compressor. A value of 0.5 means that at
/// `HIGH_FREQ_RATIO_ROLLOFF_FREQUENCY` Hz, the compression ratio will be 0.5 times that as the
/// one at 0 Hz.
pub high_freq_ratio_rolloff: FloatParam,
/// The compression knee width, in decibels.
pub knee_width_db: FloatParam,
@ -876,12 +882,6 @@ impl CompressorBank {
params.compressors.downwards.high_freq_ratio_rolloff.value();
let upwards_high_freq_ratio_rolloff =
params.compressors.upwards.high_freq_ratio_rolloff.value();
// TODO: Use 20 kHz instead of nyquist to avoid the plugin becoming brighter at higher
// sample rates
let log2_nyquist_freq = self
.log2_freqs
.last()
.expect("The CompressorBank has not yet been resized");
if self
.should_update_downwards_thresholds
@ -959,7 +959,7 @@ impl CompressorBank {
.iter()
.zip(self.downwards_ratio_recips.iter_mut())
{
let octave_fraction = log2_freq / log2_nyquist_freq;
let octave_fraction = log2_freq / HIGH_FREQ_RATIO_ROLLOFF_FREQUENCY;
let rolloff_t = octave_fraction * downwards_high_freq_ratio_rolloff;
// If the octave fraction times the rolloff amount is high, then this should get
// closer to `high_freq_ratio_rolloff` (which is in [0, 1]).
@ -982,7 +982,7 @@ impl CompressorBank {
.iter()
.zip(self.upwards_ratio_recips.iter_mut())
{
let octave_fraction = log2_freq / log2_nyquist_freq;
let octave_fraction = log2_freq / HIGH_FREQ_RATIO_ROLLOFF_FREQUENCY;
let rolloff_t = octave_fraction * upwards_high_freq_ratio_rolloff;
*ratio = (target_ratio_recip * (1.0 - rolloff_t)) + rolloff_t;
}