openCV waitKey

#include <opencv2/opencv.hpp>

int main() {
    cv::VideoCapture cap(0);

    if (!cap.isOpened()) {
        return -1;
    }

    while (true) {
        cv::Mat frame;
        cap >> frame;

        if (frame.empty()) {
            break;
        }

        cv::imshow("Video", frame);

        int key = cv::waitKey(30);

        if (key == 27) { // ASCII code for Esc key
            break;
        }
    }

    return 0;
}