signal_conditioner.h

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

struct SignalConditionerConfig {
    bool enableDCRemoval = true;

    bool enableSpikeFilter = true;

    bool enableNoiseGate = true;

    i16 spikeThreshold = 10000;

    i16 noiseGateOpenThreshold = 500;

    i16 noiseGateCloseThreshold = 300;
 
    // DC removal uses per-buffer instantaneous calculation (no alpha needed)
};

class SignalConditioner {
public:
    SignalConditioner() FL_NOEXCEPT;
    explicit SignalConditioner(const SignalConditionerConfig& config) FL_NOEXCEPT;
    ~SignalConditioner() FL_NOEXCEPT;

    void configure(const SignalConditionerConfig& config) FL_NOEXCEPT;

    Sample processSample(const Sample& sample) FL_NOEXCEPT;

    void reset() FL_NOEXCEPT;

    struct Stats {
        i32 dcOffset = 0;           // Current DC offset estimate
        bool noiseGateOpen = false; // Current noise gate state
        u32 spikesRejected = 0;     // Count of spikes rejected (lifetime)
        u32 samplesProcessed = 0;   // Total samples processed (lifetime)
    };
 
    const Stats& getStats() const FL_NOEXCEPT { return mStats; }
 
private:
    size filterSpikes(span<const i16> pcm, vector<bool>& validMask) FL_NOEXCEPT;

    i32 calculateDCOffset(span<const i16> pcm, const vector<bool>& validMask) FL_NOEXCEPT;

    void removeDCOffset(span<const i16> pcm, i32 dcOffset, vector<i16>& output) FL_NOEXCEPT;

    void applyNoiseGate(span<const i16> pcm, vector<i16>& output) FL_NOEXCEPT;
 
    SignalConditionerConfig mConfig;
    Stats mStats;

    bool mNoiseGateOpen = false;

    vector<bool> mValidMask;
    vector<i16> mTempBuffer;
    vector<i16> mOutputBuffer;
};
 
} // namespace audio
} // namespace fl