import cv2


cap = cv2.VideoCapture(20)
cap.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter.fourcc('M','J','P','G'))
cap.set(cv2.CAP_PROP_FRAME_WIDTH, 960)
cap.set(cv2.CAP_PROP_FRAME_HEIGHT, 540)

while True:
    ret, frame = cap.read()
    if ret:
        cv2.imshow("frame",frame)
    cv2.waitKey(1)
cv2.destroyAllWindows()