OpenCV + OpenCL-based face detection

#include <opencv2/ocl/ocl.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <QDateTime>
#include <QDebug>

int main()
{
    cv::ocl::OclCascadeClassifier detector;
    detector.load("/usr/share/opencv/haarcascades/haarcascade_frontalface_alt.xml");
    cv::VideoCapture capture(0);
    cv::Mat frame;
    std::vector<cv::Rect> faces;
    cv::ocl::oclMat oclFrame;

    int counter = 0;
    double uploadTime = 0;
    double detectTime = 0;
    int N = 500;
    while (counter < N && capture.read(frame))
    {
        QDateTime beforeUpload = QDateTime::currentDateTime();
        oclFrame.upload(frame);
        QDateTime afterUpload = QDateTime::currentDateTime();

        detector.detectMultiScale(oclFrame, faces);
        QDateTime afteDetect = QDateTime::currentDateTime();

        uploadTime += beforeUpload.msecsTo(afterUpload);
        detectTime += afterUpload.msecsTo(afteDetect);

        for (const auto &r : faces)
            cv::rectangle(frame, r, cv::Scalar(0, 255, 0));

        cv::imshow("test", frame);
        cv::waitKey(1);
        counter++;
    }

    uploadTime /= N;
    detectTime /= N;

    qDebug() << "uploadTime:" << uploadTime;
    qDebug() << "detectTime:" << detectTime;
}