black screen no output error in displaying video/webcam feed in OpenCV

Question

I am new to OpenCV. I want to display video/webcam feed in OpenCV.I have written the following code

import cv2
cap = cv2.VideoCapture(0)
while True:
    ret,img  = cap.read()
    cv2.imshow("Frame",img)

Instead of getting webcam feed or video, I get a black screen with no output as shown in the picture

Answer 1

You need to add cv.waitKey(1) or some other ms number as you wish. This will display a frame for 1 ms. Check the example here :

 if cv2.waitKey(1) & 0xFF == ord('q'):
        break