duration.hpp

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#ifndef EDSP_DURATION_HPP
#define EDSP_DURATION_HPP

#include <iterator>
#include <algorithm>
#include <functional>

namespace edsp { namespace feature { inline namespace temporal {

    template <typename ForwardIt, typename Numeric>
    constexpr auto duration(ForwardIt first, ForwardIt last, Numeric samplerate) {
        using value_type = typename std::iterator_traits<ForwardIt>::value_type;
        return static_cast<value_type>(std::distance(first, last)) / samplerate;
    }


    template <typename ForwardIt, typename Numeric>
    constexpr auto effective_duration(ForwardIt first, ForwardIt last, Numeric samplerate, Numeric threshold) {
        using value_type = typename std::iterator_traits<ForwardIt>::value_type;
        const auto pair        = std::minmax_element(first, last);
        const value_type limit = threshold * std::max(std::abs(pair.first), std::abs(pair.second));
        const auto get_threshold = std::find_if(first, last,
                std::bind(std::greater_equal<value_type>(), std::placeholders::_1, limit));
        const auto let_threshold = std::find_if(get_threshold, last,
                                                std::bind(std::greater_equal<value_type>(), std::placeholders::_1, limit));
        const auto samples = std::count_if(get_threshold, let_threshold);
        return static_cast<value_type>(samples) / static_cast<value_type>(samplerate);
    }
}}}

#endif //EDSP_DURATION_HPP