periodogram.hpp

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/*
 * eDSP, A cross-platform Digital Signal Processing library written in modern C++.
 * Copyright (C) 2018 Mohammed Boujemaoui Boulaghmoudi, All rights reserved.
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation, either version 3 of the License, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of  MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along width
 * this program.  If not, see <http://www.gnu.org/licenses/>
 *
 * File: periodogram.hpp
 * Author: Mohammed Boujemaoui
 * Date: 27/7/2018
 */
#ifndef EDSP_SPECTROGRAM_HPP
#define EDSP_SPECTROGRAM_HPP

#include <edsp/spectral/dft.hpp>
#include <edsp/converter/mag2db.hpp>
#include <edsp/math/numeric.hpp>
#include <vector>

namespace edsp { inline namespace spectral {

    enum class SpectralScale {
        Linear,     
        Logarithmic 
    };


    template <typename InputIt, typename OutputIt,
              typename Allocator = std::allocator<std::complex<meta::value_type_t<OutputIt>>>>
    inline void periodogram(InputIt first, InputIt last, OutputIt d_first, SpectralScale scale) {
        meta::expects(std::distance(first, last) > 0, "Not expecting empty input");
        using value_type = meta::value_type_t<InputIt>;
        const auto size  = std::distance(first, last);
        fft_impl<value_type> fft_{size};
        std::vector<std::complex<value_type>, Allocator> fft_data_(make_fft_size(size));
        fft_.dft(&(*first), meta::data(fft_data_));
        if (scale == SpectralScale::Linear) {
            std::transform(std::cbegin(fft_data_), std::cend(fft_data_), d_first,
                           [](const std::complex<value_type>& val) -> meta::value_type_t<OutputIt> {
                               return math::square(std::abs(val));
                           });
        } else {
            std::transform(std::cbegin(fft_data_), std::cend(fft_data_), d_first,
                           [](const std::complex<value_type>& val) -> meta::value_type_t<OutputIt> {
                               return converter::mag2db(std::abs(val));
                           });
        }
    }

}} // namespace edsp::spectral

#endif // EDSP_SPECTROGRAM_HPP