Detector.h

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#ifndef DETECTOR_HPP__
#define DETECTOR_HPP__
 
#include "JS8_Audio/AudioDevice.h"
 
#include <QMutex>
#include <vendor/Eigen/Dense>
 
#include <array>
 
// Output device that distributes data in predefined chunks via a signal;
// underlying device for this abstraction is just the buffer that stores
// samples throughout a receiving period.
 
class Detector : public AudioDevice {
    Q_OBJECT;

    class Filter final {
      public:
        static constexpr std::size_t NDOWN = 48 / 12;
        static constexpr std::size_t NTAPS = 49;
        static constexpr std::size_t SHIFT = NTAPS - NDOWN;
 
        using Vector = Eigen::Vector<float, NTAPS>;
        using Sample = Eigen::Map<Eigen::Vector<short, NDOWN> const>;

        explicit Filter(std::array<Vector::value_type, NTAPS> const &lowpass)
            : m_w(lowpass.data()), m_t(Vector::Zero()) {}

        auto downSample(Sample::value_type const *const data) {
            m_t.head(SHIFT) = m_t.segment(NDOWN, SHIFT);
            m_t.tail(NDOWN) = Sample(data).cast<Vector::value_type>();
 
            return static_cast<Sample::value_type>(std::round(m_w.dot(m_t)));
        }
 
      private:
        Eigen::Map<Vector const> m_w; 
        Vector m_t;                   
    };

    static constexpr std::size_t MaxBufferSize = 7 * 512;

    using Buffer = std::array<short, MaxBufferSize * Filter::NDOWN>;
 
  public:
    Detector(unsigned frameRate, unsigned periodLengthInSeconds,
             QObject *parent = nullptr);

    unsigned period() const { return m_period; }

    QMutex *getMutex() { return &m_lock; }

    void setTRPeriod(unsigned p) { m_period = p; }

    unsigned secondInPeriod() const;

    void clear();

    bool reset() override;

    void resetBufferContent();

    void resetBufferPosition();

    Q_SIGNAL void framesWritten(qint64) const;

    Q_SLOT void setBlockSize(unsigned);
 
  protected:
    qint64 readData(char *, qint64) override { return -1; }

    qint64 writeData(char const *, qint64) override;
 
  private:
    unsigned m_frameRate;               
    unsigned m_period;                  
    QMutex m_lock;                      
    Filter m_filter;                    
    Buffer m_buffer;                    
    Buffer::size_type m_bufferPos = 0;  
    std::size_t m_samplesPerFFT = MaxBufferSize; 
    qint32 m_ns = 999;                  
};
 
#endif