import cv2
import time
cap = cv2.VideoCapture(2)  # 0表示第一个摄像头
start=time.time()
while True:
    ret, frame = cap.read()
    if not ret: break
    end=time.time()
    diff=end-start
    print('cap img',1/diff)
    start=end
    ###cv2.imshow('USB Camera', frame)
    if cv2.waitKey(1) == 27: break  # 按ESC退出
cap.release()
cv2.destroyAllWindows()