Define a struct for SC analyzer data

plugins/spectral_compressor/src/analyzer.rs

@@ -0,0 +1,21 @@
+/// The data stored used for the spectrum analyzer. This also contains the gain reduction and the
+/// threshold curve (which is dynamic in the sidechain matching mode).
+///
+/// All of these values are raw gain/amplitude or dB values obtained directly from the DSP code. If
+/// this needs to be skewed for visualization then that should be done in the editor.
+///
+/// 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.
+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.
+    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)
+    /// factor in the output gain.
+    pub gain_reduction_db: [f32; crate::MAX_WINDOW_SIZE / 2 + 1],
+    // TODO: Include the threshold curve. Decide on whether to only visualizer the 'global'
+    //       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.
+}

plugins/spectral_compressor/src/lib.rs

@@ -22,6 +22,7 @@ use realfft::num_complex::Complex32;
 use realfft::{ComplexToReal, RealFftPlanner, RealToComplex};
 use std::sync::Arc;
 
+mod analyzer;
 mod compressor_bank;
 mod dry_wet_mixer;
 mod editor;