Test

import sys
import cv2
import os

from datetime import datetime

from PyQt5.QtWidgets import QApplication, QMainWindow
from PyQt5 import uic
from PyQt5.QtGui import QPixmap, QImage
from PyQt5.QtCore import QTimer


class Videolink(QMainWindow):
    def __init__(self):
        super().__init__()
        uic.loadUi('videolink_main.ui', self)

        self.timerVideo = QTimer(self)

        self.startbtn.clicked.connect(self.startTime)
        self.endbtn.clicked.connect(self.endTime)
        self.cap = cv2.VideoCapture(cv2.CAP_DSHOW, 0)
        self.cap.set(3, 480)
        self.cap.set(4, 640)
        self.cap.set(5, 30)

    def viewCam(self):
        ret, image = self.cap.read()
        im = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
        height, width, channel = im.shape
        step = channel * width
        qImg = QImage(im.data, width, height, step, QImage.Format_RGB888)
        self.ui.screen.setPixmap(QPixmap.fromImage(qImg))

    def startTime(self):
        self.timerVideo.start()
        self.timerVideo.timeout.connect(self.viewCam)

    def endTime(self):
        self.timerVideo.stop()
        self.screen.clear()

if __name__ == "__main__":
    app = QApplication(sys.argv)
    exe = Videolink()
    exe.show()
    sys.exit(app.exec())