Working version of https://gist.github.com/RomanSteinberg/e7a2d6a99f198670be48bede0b9f1cb3

working-numpy-pybind11.cpp

#include <vector>
#include <iostream>

#include <pybind11/pybind11.h>
#include <pybind11/embed.h>
#include <pybind11/stl.h>
#include <pybind11/numpy.h>

struct FrameInfo
{
    using first_type = std::vector<int>;
    using second_type = std::vector<std::vector<std::vector<int>>>;

private:
    first_type result1;
    second_type result2;

public:
    FrameInfo(first_type const &a, second_type const &b) : result1(a), result2(b){};
};

namespace py = pybind11;

FrameInfo *send_frame(int height, int width, const uint8_t *data)
{
    try {
        py::module_ api_module = py::module_::import("api");

        pybind11::dtype dt("uint8");
        const int shape[3] = {height, width, 3};
        py::array py_frame(dt, shape, data);
        py::tuple result = api_module.attr("refine_frame")(py_frame);
        auto b = result[0].cast<std::vector<int>>();
        auto c = result[1].cast<std::vector<std::vector<std::vector<int>>>>();
        return new FrameInfo(b, c);
    }
    catch (py::error_already_set const& ex) {
        std::cout << "error: " << ex.what() << "\n";
        return nullptr;
    }
}

void test_foo()
{
    int height = 4, width = 5, depth = 3;
    std::vector<uint8_t> data(height * width * depth);

    for (int i = 0; i < 10; ++i)
    {   std::cout << "loop " << i << "\n";
        FrameInfo *fi = send_frame(height, width, data.data());

        if (!fi) {
            break;
        }
    }
}

int main()
{
    py::scoped_interpreter guard{}; // start the interpreter and keep it alive

    py::exec(R"(
            import site
            site.addsitedir("lib")

            print("site.addsitedir() done")
        )");

    test_foo();
    return EXIT_SUCCESS;
}