Add triple buffers to share analyzer data in SC

Cargo.lock

@@ -3762,6 +3762,7 @@ dependencies = [
  "open",
  "realfft",
  "serde",
+ "triple_buffer",
 ]
 
 [[package]]

plugins/diopser/src/spectrum.rs

@@ -30,8 +30,8 @@ const SPECTRUM_WINDOW_OVERLAP: usize = 2;
 /// peak meter.
 const SMOOTHING_DECAY_MS: f32 = 100.0;
 
-/// The amplitudes of all frequency bins in a windowed FFT of the input. Also includes the DC offset
-/// bin which we don't draw, just to make this a bit less confusing.
+/// The amplitudes of all frequency bins in a windowed FFT of Diopser's output. Also includes the DC
+/// offset bin which we don't draw, just to make this a bit less confusing.
 pub type Spectrum = [f32; SPECTRUM_WINDOW_SIZE / 2 + 1];
 /// A receiver for a spectrum computed by [`SpectrumInput`].
 pub type SpectrumOutput = triple_buffer::Output<Spectrum>;

plugins/spectral_compressor/Cargo.toml

@@ -19,3 +19,4 @@ realfft = "3.0"
 crossbeam = "0.8"
 open = "3.0"
 serde = { version = "1.0", features = ["derive"] }
+triple_buffer = "6.2"

plugins/spectral_compressor/src/analyzer.rs

@@ -7,9 +7,13 @@
 /// This pulls the data directly from the spectral compression part of Spectral Compressor, so the
 /// window size and overlap amounts are equal to the ones used by SC's main algorithm. If the
 /// current window size is 2048, then only the first `2048 / 2 + 1` elements in the arrays are used.
+#[derive(Debug)]
 pub struct AnalyzerData {
     /// The amplitudes of all frequency bins in a windowed FFT of Spectral Compressor's output. Also
     /// includes the DC offset bin which we don't draw, just to make this a bit less confusing.
+    ///
+    /// This data is taken directly from the envelope followers, so it has the same rise and fall
+    /// time as what is used by the compressors.
     pub spectrum: [f32; crate::MAX_WINDOW_SIZE / 2 + 1],
     /// The gain reduction applied to each band, in decibels. Positive values mean that a band
     /// becomes louder, and negative values mean a band got attenuated. Does not (and should not)
@@ -19,3 +23,12 @@ pub struct AnalyzerData {
     //       threshold curve or to also show the individual upwards/downwards thresholds. Or omit
     //       this and implement it in a nicer way for the premium Spectral Compressor.
 }
+
+impl Default for AnalyzerData {
+    fn default() -> Self {
+        Self {
+            spectrum: [0.0; crate::MAX_WINDOW_SIZE / 2 + 1],
+            gain_reduction_db: [0.0; crate::MAX_WINDOW_SIZE / 2 + 1],
+        }
+    }
+}

plugins/spectral_compressor/src/compressor_bank.rs

@@ -19,6 +19,7 @@ use realfft::num_complex::Complex32;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::Arc;
 
+use crate::analyzer::AnalyzerData;
 use crate::SpectralCompressorParams;
 
 // These are the parameter name prefixes used for the downwards and upwards compression parameters.
@@ -97,6 +98,11 @@ pub struct CompressorBank {
     /// The sample rate this compressor bank was configured for. This is used to compute the
     /// coefficients for the envelope followers in the process function.
     sample_rate: f32,
+
+    /// The input data for the spectrum analyzer. Stores both the spectrum analyzer values and the
+    /// current gain reduction. Used to draw the spectrum analyzer and gain reduction display in the
+    /// editor.
+    analyzer_input_data: triple_buffer::Input<AnalyzerData>,
 }
 
 #[derive(Params)]
@@ -393,7 +399,11 @@ impl CompressorParams {
 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 {
+    pub fn new(
+        analyzer_input_data: triple_buffer::Input<AnalyzerData>,
+        num_channels: usize,
+        max_window_size: usize,
+    ) -> Self {
         let complex_buffer_len = max_window_size / 2 + 1;
 
         CompressorBank {
@@ -423,6 +433,8 @@ impl CompressorBank {
             ],
             window_size: 0,
             sample_rate: 1.0,
+
+            analyzer_input_data,
         }
     }
 

plugins/spectral_compressor/src/lib.rs

@@ -14,13 +14,15 @@
 // 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 analyzer::AnalyzerData;
 use crossbeam::atomic::AtomicCell;
 use editor::EditorMode;
 use nih_plug::prelude::*;
 use nih_plug_vizia::ViziaState;
 use realfft::num_complex::Complex32;
 use realfft::{ComplexToReal, RealFftPlanner, RealToComplex};
-use std::sync::Arc;
+use std::sync::{Arc, Mutex};
+use triple_buffer::TripleBuffer;
 
 mod analyzer;
 mod compressor_bank;
@@ -69,6 +71,10 @@ pub struct SpectralCompressor {
     plan_for_order: Option<[Plan; MAX_WINDOW_ORDER - MIN_WINDOW_ORDER + 1]>,
     /// The output of our real->complex FFT.
     complex_fft_buffer: Vec<Complex32>,
+
+    /// The output for the analyzer data computed in `CompressorBank` while the editor is open. This
+    /// can be cloned and moved into the editor.
+    analyzer_output_data: Arc<Mutex<triple_buffer::Output<AnalyzerData>>>,
 }
 
 /// An FFT plan for a specific window size, all of which will be precomputed during initilaization.
@@ -141,9 +147,15 @@ pub struct GlobalParams {
 
 impl Default for SpectralCompressor {
     fn default() -> Self {
+        // The spectrum analyzer and gain reduction data is computed directly in the spectral
+        // compression routine in `compressor_bank`. `analyzer_output_data` can then be used in the
+        // editor to draw the data.
+        let (analyzer_input_data, analyzer_output_data) = TripleBuffer::default().split();
+
         // Changing any of the compressor threshold or ratio parameters will set an atomic flag in
         // this object that causes the compressor thresholds and ratios to be recalcualted
-        let compressor_bank = compressor_bank::CompressorBank::new(2, MAX_WINDOW_SIZE);
+        let compressor_bank =
+            compressor_bank::CompressorBank::new(analyzer_input_data, 2, MAX_WINDOW_SIZE);
 
         SpectralCompressor {
             params: Arc::new(SpectralCompressorParams::new(&compressor_bank)),
@@ -165,6 +177,8 @@ impl Default for SpectralCompressor {
             // the plugin is initialized
             plan_for_order: None,
             complex_fft_buffer: Vec::with_capacity(MAX_WINDOW_SIZE / 2 + 1),
+
+            analyzer_output_data: Arc::new(Mutex::new(analyzer_output_data)),
         }
     }
 }