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Apply downwards compression to DC bins

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In Spectral Compressor. We avoided this because it messes up upwards
compression, but downwards compression is perfectly fine.
This commit is contained in:
Robbert van der Helm 2022-09-04 15:07:23 +02:00
parent 5faed9e2e7
commit 08b1e43a15
1 changed files with 16 additions and 32 deletions
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48
plugins/spectral_compressor/src/compressor_bank.rs
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@ -512,39 +512,35 @@ impl CompressorBank {
/// Apply the magnitude compression to a buffer of FFT bins. The compressors are first updated
/// if needed. The overlap amount is needed to compute the effective sample rate. The
/// `skip_bins_below` argument is used to avoid compressing DC bins, or the neighbouring bins
/// the DC signal may have been convolved into because of the Hann window function.
/// `first_non_dc_bin` argument is used to avoid upwards compression on the DC bins, or the
/// neighbouring bins the DC signal may have been convolved into because of the Hann window
/// function.
pub fn process(
&mut self,
buffer: &mut [Complex32],
channel_idx: usize,
params: &SpectralCompressorParams,
overlap_times: usize,
skip_bins_below: usize,
first_non_dc_bin: usize,
) {
nih_debug_assert_eq!(buffer.len(), self.log2_freqs.len());
self.update_if_needed(params);
match params.threshold.mode.value() {
ThresholdMode::Internal => {
self.update_envelopes(buffer, channel_idx, params, overlap_times, skip_bins_below);
self.compress(buffer, channel_idx, params, skip_bins_below)
self.update_envelopes(buffer, channel_idx, params, overlap_times);
self.compress(buffer, channel_idx, params, first_non_dc_bin)
}
ThresholdMode::SidechainMatch => {
self.update_envelopes(buffer, channel_idx, params, overlap_times, skip_bins_below);
self.compress_sidechain_match(buffer, channel_idx, params, skip_bins_below)
self.update_envelopes(buffer, channel_idx, params, overlap_times);
self.compress_sidechain_match(buffer, channel_idx, params, first_non_dc_bin)
}
ThresholdMode::SidechainCompress => {
// This mode uses regular compression, but the envelopes are computed from the
// sidechain input magnitudes. These are already set in `process_sidechain`. This
// separate envelope updating function is needed for the channel linking.
self.update_envelopes_sidechain(
channel_idx,
params,
overlap_times,
skip_bins_below,
);
self.compress(buffer, channel_idx, params, skip_bins_below)
self.update_envelopes_sidechain(channel_idx, params, overlap_times);
self.compress(buffer, channel_idx, params, first_non_dc_bin)
}
};
}
@ -565,7 +561,6 @@ impl CompressorBank {
channel_idx: usize,
params: &SpectralCompressorParams,
overlap_times: usize,
skip_bins_below: usize,
) {
// The coefficient the old envelope value is multiplied by when the current rectified sample
// value is above the envelope's value. The 0 to 1 step response retains 36.8% of the old
@ -591,11 +586,7 @@ impl CompressorBank {
};
let release_new_t = 1.0 - release_old_t;
for (bin, envelope) in buffer
.iter()
.zip(self.envelopes[channel_idx].iter_mut())
.skip(skip_bins_below)
{
for (bin, envelope) in buffer.iter().zip(self.envelopes[channel_idx].iter_mut()) {
let magnitude = bin.norm();
if *envelope > magnitude {
// Release stage
@ -616,7 +607,6 @@ impl CompressorBank {
channel_idx: usize,
params: &SpectralCompressorParams,
overlap_times: usize,
skip_bins_below: usize,
) {
// See `update_envelopes()`
let effective_sample_rate =
@ -641,11 +631,7 @@ impl CompressorBank {
let other_channels_t = params.threshold.sc_channel_link.value / num_channels;
let this_channel_t = 1.0 - (other_channels_t * (num_channels - 1.0));
for (bin_idx, envelope) in self.envelopes[channel_idx]
.iter_mut()
.enumerate()
.skip(skip_bins_below)
{
for (bin_idx, envelope) in self.envelopes[channel_idx].iter_mut().enumerate() {
// In this mode the envelopes are set based on the sidechain signal, taking channel
// linking into account
let sidechain_magnitude: f32 = self
@ -697,7 +683,7 @@ impl CompressorBank {
buffer: &mut [Complex32],
channel_idx: usize,
params: &SpectralCompressorParams,
skip_bins_below: usize,
first_non_dc_bin: usize,
) {
// Well I'm not sure at all why this scaling works, but it does. With higher knee
// bandwidths, the middle values needs to be pushed more towards the post-knee threshold
@ -723,7 +709,6 @@ impl CompressorBank {
.iter_mut()
.zip(self.envelopes[channel_idx].iter())
.enumerate()
.skip(skip_bins_below)
{
// This works by computing a scaling factor, and then scaling the bin magnitudes by that.
let mut scale = 1.0;
@ -752,7 +737,7 @@ impl CompressorBank {
let upwards_ratio_recip = unsafe { self.upwards_ratio_recips.get_unchecked(bin_idx) };
let upwards_knee_start = unsafe { self.upwards_knee_starts.get_unchecked(bin_idx) };
let upwards_knee_end = unsafe { self.upwards_knee_ends.get_unchecked(bin_idx) };
if *upwards_ratio_recip != 1.0 && *envelope > 1e-6 {
if bin_idx >= first_non_dc_bin && *upwards_ratio_recip != 1.0 && *envelope > 1e-6 {
scale *= compress_upwards(
*envelope,
*upwards_threshold,
@ -779,7 +764,7 @@ impl CompressorBank {
buffer: &mut [Complex32],
channel_idx: usize,
params: &SpectralCompressorParams,
skip_bins_below: usize,
first_non_dc_bin: usize,
) {
// See `compress` for more details
let downwards_knee_scaling_factor =
@ -805,7 +790,6 @@ impl CompressorBank {
.iter_mut()
.zip(self.envelopes[channel_idx].iter())
.enumerate()
.skip(skip_bins_below)
{
// The idea here is that we scale the compressor thresholds/knee values by the sidechain
// signal, thus sort of creating a dynamic multiband compressor
@ -855,7 +839,7 @@ impl CompressorBank {
unsafe { self.upwards_knee_starts.get_unchecked(bin_idx) * sidechain_scale };
let upwards_knee_end =
unsafe { self.upwards_knee_ends.get_unchecked(bin_idx) * sidechain_scale };
if *upwards_ratio_recip != 1.0 && *envelope > 1e-6 {
if bin_idx >= first_non_dc_bin && *upwards_ratio_recip != 1.0 && *envelope > 1e-6 {
scale *= compress_upwards(
*envelope,
upwards_threshold,