Initial BEAMGRID VST3/AU spectrum analyzer

Source/Analyser.h

@@ -0,0 +1,74 @@
+#pragma once
+
+#include "JuceHeader.h"
+
+// Beamgrid analyser: log-spaced spectrum bands with peak-hold markers.
+// Each band tracks a current level and a peak that holds for a definable
+// "grace" time before falling off at a definable rate.
+class Analyser
+{
+public:
+    static constexpr int maxBands = 256;
+    enum { fftOrder = 11, fftSize = 1 << fftOrder, fftBins = fftSize / 2 };
+
+    Analyser();
+
+    void prepare (double sampleRate, int blockSize);
+    void push (const float* channelData, int numSamples);
+    void update (double dt);
+
+    int getNumBands() const noexcept { return numBands; }
+    float getLevel (int band) const noexcept { return band < numBands ? juce::jmin (1.0f, levels[band]) : 0.0f; }
+    float getPeak  (int band) const noexcept { return band < numBands ? juce::jmin (1.0f, peaks[band]) : 0.0f; }
+
+    // Helpers for drawing axis legends.
+    double getMinFreq() const noexcept { return minFreq; }
+    double getMaxFreq() const noexcept { return maxFreq; }
+    float freqToFraction (double freq) const noexcept;
+    float dbToFraction (double db) const noexcept;
+
+    void setGraceSeconds (double seconds) noexcept { grace = seconds; }
+    void setFalloffRate  (double rate)    noexcept { falloffRate = rate; }
+    void setBarReleaseTau (double seconds) noexcept { barReleaseTau = seconds; }
+    void setNumBands (int n) noexcept;
+    double getGraceSeconds() const noexcept { return grace; }
+    double getFalloffRate()  const noexcept { return falloffRate; }
+
+private:
+    void pushSample (float sample);
+    void computeFFT();
+    void computeBandEdges();
+
+    juce::dsp::FFT fft { fftOrder };
+    juce::dsp::WindowingFunction<float> window { fftSize, juce::dsp::WindowingFunction<float>::hann, true };
+
+    // Sliding time-domain window so the FFT is recomputed every `hopSize`
+    // samples (overlapped) instead of only once per full window. This keeps
+    // the visualization temporally smooth.
+    static constexpr int hopSize = 256;
+
+    std::array<float, fftSize>       ring {};
+    std::array<float, 2 * fftSize>   fftData {};
+    int writePos = 0;
+    int samplesSinceFFT = 0;
+    int totalSamples = 0;
+
+    int numBands = 64;
+    std::array<float, maxBands> levels {};
+    std::array<float, maxBands> targets {};
+    std::array<float, maxBands> peaks {};
+    std::array<float, maxBands> peakTimers {};
+
+    // First/last FFT bin index covered by each band (log spaced).
+    std::array<int, maxBands + 1> bandBinEdges {};
+
+    double minFreq = 20.0;
+    double maxFreq = 22050.0;
+
+    double sampleRate = 44100.0;
+    double grace = 0.8;        // seconds the peak is held before falling
+    double falloffRate = 0.8;  // normalized units per second while falling
+    double barReleaseTau = 0.2; // seconds for the live bar to fall (release)
+    double minDb = -48.0;      // dBFS-equivalent floor (bands below this -> 0)
+    double maxDb = -6.0;       // dBFS-equivalent ceiling (bands at/above -> 1)
+};