python - Difference in output with waitKey(0) and waitKey(1)

Question

I've just begun using the OpenCV library for Python and came across something I didn't understand.

cap = cv2.VideoCapture(0)

while True:
      ret, frame = cap.read() #returns ret and the frame
      cv2.imshow('frame',frame)

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

When I use cv2.waitKey(1), I get a continuous live video feed from my laptops webcam. However when I use cv2.waitKey(0), I get still images. Every time I close the window, another one pops up with another picture taken at the time. Why does it not show as a continuous feed?

Answer 1

From the doc:

1.waitKey(0) will display the window infinitely until any keypress (it is suitable for image display).

2.waitKey(1) will display a frame for 1 ms, after which display will be automatically closed. Since the OS has a minimum time between switching threads, the function will not wait exactly 1 ms, it will wait at least 1 ms, depending on what else is running on your computer at that time.

So, if you use waitKey(0) you see a still image until you actually press something while for waitKey(1) the function will show a frame for at least 1 ms only.