multiband_beat_detector.h

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#pragma once
 
#include "fl/stl/int.h"
#include "fl/stl/span.h"
#include "fl/stl/noexcept.h"
 
namespace fl {
namespace audio {
namespace detector {

struct MultiBandBeatDetectorConfig {
    float bassThreshold = 0.15f;

    float midThreshold = 0.12f;

    float trebleThreshold = 0.08f;

    u32 beatCooldownFrames = 10;

    bool enableCrossBandCorrelation = true;

    float correlationBoost = 0.05f;
};

class MultiBandBeat {
public:
    MultiBandBeat() FL_NOEXCEPT;
    explicit MultiBandBeat(const MultiBandBeatDetectorConfig& config);
    ~MultiBandBeat() FL_NOEXCEPT;

    void configure(const MultiBandBeatDetectorConfig& config);

    void detectBeats(span<const float> frequencyBins);

    bool isBassBeat() const;

    bool isMidBeat() const;

    bool isTrebleBeat() const;

    float getBassEnergy() const;

    float getMidEnergy() const;

    float getTrebleEnergy() const;

    bool isMultiBandBeat() const;

    void reset();

    struct Stats {
        u32 bassBeats = 0;          // Total bass beats detected (lifetime)
        u32 midBeats = 0;           // Total mid beats detected (lifetime)
        u32 trebleBeats = 0;        // Total treble beats detected (lifetime)
        u32 multiBandBeats = 0;     // Beats with multiple bands (lifetime)
        float bassEnergy = 0.0f;    // Current bass energy
        float midEnergy = 0.0f;     // Current mid energy
        float trebleEnergy = 0.0f;  // Current treble energy
    };
 
    const Stats& getStats() const { return mStats; }
 
private:
    bool detectBandBeat(float currentEnergy, float previousEnergy,
                       float threshold, u32& cooldownCounter);

    float calculateBassEnergy(span<const float> frequencyBins) const;

    float calculateMidEnergy(span<const float> frequencyBins) const;

    float calculateTrebleEnergy(span<const float> frequencyBins) const;
 
    MultiBandBeatDetectorConfig mConfig;
    Stats mStats;

    bool mBassBeat = false;
    bool mMidBeat = false;
    bool mTrebleBeat = false;

    float mBassEnergy = 0.0f;
    float mMidEnergy = 0.0f;
    float mTrebleEnergy = 0.0f;

    float mPreviousBassEnergy = 0.0f;
    float mPreviousMidEnergy = 0.0f;
    float mPreviousTrebleEnergy = 0.0f;

    u32 mBassCooldown = 0;
    u32 mMidCooldown = 0;
    u32 mTrebleCooldown = 0;

    u32 mCurrentFrame = 0;

    static constexpr size BASS_BIN_START = 0;
    static constexpr size BASS_BIN_END = 2;    // Bins 0-1
    static constexpr size MID_BIN_START = 6;
    static constexpr size MID_BIN_END = 8;     // Bins 6-7
    static constexpr size TREBLE_BIN_START = 14;
    static constexpr size TREBLE_BIN_END = 16; // Bins 14-15
};
 
} // namespace detector
} // namespace audio
} // namespace fl