snr.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/>
*
* Filename: snr.hpp
* Author: Mohammed Boujemaoui
* Date: 10/10/18
*/

#ifndef EDSP_SNR_HPP
#define EDSP_SNR_HPP

#include <edsp/meta/iterator.hpp>
#include <edsp/statistics/variance.hpp>
#include <edsp/converter/pow2db.hpp>
#include <vector>

namespace edsp { namespace statistics {

    template <typename InputIt, typename Allocator = std::allocator<meta::value_type_t<InputIt>>>
    constexpr meta::value_type_t<InputIt> snr(InputIt first1, InputIt last1, InputIt first2) {
        using value_type = meta::value_type_t<InputIt>;
        const auto N     = std::distance(first1, last1);
        std::vector<value_type, Allocator> noise(N);
        std::transform(first1, last1, first2, std::begin(noise),
                       [](const value_type left, const value_type right) { return left - right; });

        const auto var_ref   = statistics::variance(first1, first2);
        const auto var_noise = statistics::variance(std::cbegin(noise), std::cend(noise));
        return converter::pow2db(var_ref / var_noise);
    }

}}     // namespace edsp::statistics
#endif //EDSP_SNR_HPP