InstaGrain/Source/Grain.h

#pragma once
#include <JuceHeader.h>

// ============================================================
// Hann window lookup table (1024 points, computed once)
// ============================================================
struct GrainWindow
{
    static constexpr int tableSize = 1024;
    float table[tableSize];

    GrainWindow()
    {
        for (int i = 0; i < tableSize; ++i)
        {
            float phase = (float) i / (float) (tableSize - 1);
            table[i] = 0.5f * (1.0f - std::cos (juce::MathConstants<float>::twoPi * phase));
        }
    }

    float getValue (float phase) const
    {
        float index = juce::jlimit (0.0f, 1.0f, phase) * (float) (tableSize - 1);
        int i0 = (int) index;
        int i1 = std::min (i0 + 1, tableSize - 1);
        float frac = index - (float) i0;
        return table[i0] + frac * (table[i1] - table[i0]);
    }
};

// ============================================================
// Single grain
// ============================================================
struct Grain
{
    int startSample = 0;            // where in source buffer
    int lengthSamples = 0;          // grain duration in samples
    float pitchRatio = 1.0f;        // playback speed
    double readPosition = 0.0;      // current fractional read position
    int samplesElapsed = 0;         // output samples generated
    float panPosition = 0.0f;       // -1 left, +1 right
    float volume = 1.0f;
    bool reverse = false;
    bool active = false;
};