CODEWITHSUNDEEP
pythonopencvfreezeopencv3.0
Huy Le
Huy Le

Reputation: 1738

Python OpenCV cv2.waitKey(1) cause video window to freeze/not responding

So I'm running this piece of code.

import cv2
frameWidth = 640
frameHeight = 480
cap = cv2.VideoCapture("Resources/test_video.mp4")
while True:
    success, img = cap.read()
    if img is None:
        break
    img = cv2.resize(img, (frameWidth, frameHeight))
    cv2.imshow("Result", img)
    keyPressed = cv2.waitKey(5)
    if keyPressed == ord('q'):
        break;

test_video.mp4 is a short video here The moment it finishes running, the "Result" window freezes and become not responding. Even when I press "Q", nothing happens.

I run the program on Anaconda Spyder. cv2 is installed using pip install opencv-python

Edit: the code has been fixed so that the window exit when "q" is pressed

Upvotes: 0

Views: 1665

Answers (1)

Robert Young
Robert Young

Reputation: 456

Try adding these two lines at the end:

import cv2
frameWidth = 640
frameHeight = 480
cap = cv2.VideoCapture("Resources/test_video.mp4")
    while True:
        success, img = cap.read()
        if img is None:
            break
        #img = cv2.resize(img, (frameWidth, frameHeight))
        cv2.imshow("Result", img)
        if cv2.waitKey(1) and 0xFF == ord('q'):
             break
cap.release()
cv2.destroyAllWindows()

It could be that it's failing to release the resource at the end of the script. See this post for further reference: What's the meaning of cv2.videoCapture.release()?

It also seems to be a common issue. See here and here.

Edit: Update to respond to comment requesting video exit on 'q'. Replace the lines:

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

With:

key = cv2.waitKey(1)
if key == ord('q'):
    break

Tested and behaviour is as expected using:

  • Python 3.7
  • OpenCV 3.4.2

Upvotes: 3

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