detector.h

#pragma once
 
#include <optional>
#include <memory>
 
#include <dsplib/array.h>
 
namespace dsplib {
 
class PreambleDetectorImpl;
 
// Preamble signal detector (only complex signal)
//
// Equivalent Matlab formula:
// function [res] = detector(x, h)
// nh = length(h);
// corr = filter(conj(h) / (nh * rms(h)), 1, x);
// pagg = filter(ones(1, nh) / nh, 1, abs(x).^2);
// res = sqrt((abs(corr) .^ 2) ./ pagg);
//TODO: add real type implementation
class PreambleDetector
{
public:
    explicit PreambleDetector(span_cmplx h, real_t threshold = 0.5);
 
    PreambleDetector(const PreambleDetector&) = delete;
 
    struct Result
    {
        int offset{0};        
        arr_cmplx preamble;   
        real_t score{0};      
    };
 
    //TODO: add bypass mode
    //length of the 'sig' must be a multiple of 'frame_len()'
    std::optional<Result> process(span_cmplx x);
 
    std::optional<Result> operator()(span_cmplx x) {
        return this->process(x);
    }
 
    [[nodiscard]] int frame_len() const noexcept;
 
    void reset();
 
private:
    std::shared_ptr<PreambleDetectorImpl> _d;
};
 
}   // namespace dsplib