Why is opencv splitting an image into parts?

Question

ubuntu

then opencv, when capturing an image from a webcam, divides it into 2 parts, and it turns out that the lower part of the image is on top and the upper one is on the bottom?

#include <opencv2/opencv.hpp>
#include <iostream>
using namespace std;
using namespace cv;

int main(){

    VideoCapture vcap(0);

    if(!vcap.isOpened()){
        cout << "Error opening video stream" << endl;
        return -1;
    }

    namedWindow("Frame",cv::WINDOW_NORMAL);
    for(;;){

        Mat frame;
        vcap.read(frame);
        imshow( "Frame", frame );
        char c = (char)waitKey(33);
        if( c == 27 ) break;
    }
    return 0;
}