使用 CUDA 加速 FFmpeg 编码 HEVC

#include <filesystem>
#include <format>
#include <iostream>
#include <deque>

namespace fs = std::filesystem;

template<typename T> requires requires(T t,typename T::value_type u) { t.push_back(u); }
void recursive_find_video(const fs::path& p, T& v_p)
{
    auto begin = fs::recursive_directory_iterator(p);
    auto end = fs::recursive_directory_iterator();
    while (begin != end)
    {
        try {
            const auto& entry = *begin;
            if (entry.is_regular_file())
            {
                const auto ext = entry.path().extension().string();
                if (ext == ".mp4" || ext == ".mkv") {
                    v_p.push_back(entry.path());
                    std::cout << "Added " << entry.path() << " to list." << std::endl;
                }
            }
            else {
                // other mysterious type
            }
            ++begin;
        }
        catch (fs::filesystem_error a) {
            ++begin;
        }
    }
}

// std::format针对std::filesystem::path的重载，实际没啥用，仅用于省略format参数中的path::string()
template<> class std::formatter<fs::path, char>
: public std::_Formatter_base<fs::path, char, std::_Basic_format_arg_type::_Custom_type>
// _Basic_format_arg_type是个枚举类，_Custom_type用于说明是自定义类型
{
protected:
    // 根据自定义类型的成员变量类型，定义一些内置的std::formatter对象
    formatter<string, char> string_formatter;
public:
    using _BaseClass = _Formatter_base<fs::path, char, std::_Basic_format_arg_type::_Custom_type>;
    // 直接借用了基类的parse，无实际作用
    using _ParseContext = basic_format_parse_context<char>;
    _ParseContext::iterator parse(_ParseContext& parse_ctx)
    { // parse用于解析格式化符
        return _BaseClass::parse(parse_ctx);
    }
    using _FormatContext = basic_format_context<back_insert_iterator<_Fmt_buffer<char>>, char>;
    _FormatContext::iterator format(const fs::path& val, _FormatContext& format_ctx) noexcept
    { // format负责具体输出
        back_insert_iterator<_Fmt_buffer<char>> itor = format_ctx.out();
        itor = string_formatter.format(val.string(), format_ctx);
        return itor;
    }

};

int main()
{
    std::vector<fs::path> v_p;
    recursive_find_video(fs::current_path(), v_p);
    for(auto &p1:v_p) {
        fs::path p2 = p1.parent_path();
        p2 /= p1.stem();
        p2 += "_temp";
        p2 += p1.extension();
        std::system(std::format("ffmpeg -i \"{}\" -map 0 -c copy -c:v hevc_nvenc -preset slow -tune 1 -b:v 5000k -profile:v main10 -level 6 -b_ref_mode 1 -bf 4 -c:a copy \"{}\"",
            p1, p2).c_str());
        fs::remove(p1);
        fs::rename(p2, p1);
    }
}