CV2: “[ WARN:0] terminating async callback” when attempting to take a picture

Question

I am trying to take a picture from the defualt carmera with python, to do this I am using openCV (import cv2 from python shell). However, when I attempt to disable the camera it closes but with the error [ WARN:0] terminating async callback.

This is code I am trying to run:

import cv2

camera_port = 0
camera = cv2.VideoCapture(camera_port)
return_value, image = camera.read()
cv2.imwrite("image.png", image)

camera.release() # Error is here

The code outputs the desired result- it takes a saves an image but I do not understand why the error message occures or how to remove it

Answer 1

It's probably showing a warning because you're not releasing the handle to the webcam.

try adding this to the end of the code

camera.release()
cv2.destroyAllWindows()

I hope this helps!

Answer 2

I had the same warning. Just modify the line camera = cv2.VideoCapture(camera_port) to camera = cv2.VideoCapture(camera_port, cv2.CAP_DSHOW) and add cv2.destroyAllWindows() as the last line of your code.

Answer 3

camera = cv2.VideoCapture(camera_port,cv2.CAP_DSHOW)

cv2.destroyAllWindows()

Answer 4

It works for me as indicated Sumit Kumar

camera_port = 0
#camera = cv2.VideoCapture(camera_port)
camera = cv2.VideoCapture(camera_port,cv2.CAP_DSHOW)
# Check if the webcam is opened correctly
if not camera.isOpened():
    raise IOError("Cannot open webcam")

return_value, image = camera.read()
print("We take a picture of you, check the folder")
cv2.imwrite("image.png", image)

camera.release() # Error is here
cv2.destroyAllWindows()

Answer 5

1. first:add cv2.destroyAllWindows()
2. second:the camera permission you have banned,and then check it.

Answer 6

I did this & I don't see that warning there after.(only for Windows OS)

Open cmd and type:

setx OPENCV_VIDEOIO_PRIORITY_MSMF 0