Webcam works inconsistently [closed]

asked 2018-12-17 07:06:40 -0500

kgpinco gravatar image


I have searched for answer to this error for a few days now as I have seen people getting the same error however none of the solutions I came across worked.
I created a simple program to do nothing other than load in the camera:

import cv2

cap = cv2.VideoCapture(0)

# Check if the webcam is opened correctly
if not cap.isOpened():
    raise IOError("Cannot open webcam")

while True:
    ret, frame =
    cv2.imshow('Input', frame)

    c = cv2.waitKey(1)
    if c == 27:


Though, sometimes my webcam loads in with no problems most of time doesn't work with the error messages:

[ WARN:0] videoio(MSMF): OnReadSample() is called with error status: -2147024894 [ WARN:0] videoio(MSMF): async ReadSample() call is failed with error status: -2147024894 [ WARN:1] videoio(MSMF): can't grab frame. Error: -2147024894 cv2.error: OpenCV(3.4.4) C:\projects\opencv-python\opencv\modules\highgui\src\window.cpp:356: error: (-215:Assertion failed) size.width>0 && size.height>0 in function 'cv::imshow

I have seen many answers talk about the camera capture being empty and it not expecting an empty value: though they don't explain WHY it is empty and how to prevent it.

Any help is greatly appreciated.

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Closed for the following reason question is not relevant or outdated by sturkmen
close date 2020-11-09 10:19:56.995999


There is no onReadSample() in opencv

LBerger gravatar imageLBerger ( 2018-12-17 07:23:28 -0500 )edit

maybe you can try to use the dshow backend, instead of the MSMF one ?

cap = cv2.VideoCapture(0 + cv2.CAP_DSHOW)

error is from here, btw.

berak gravatar imageberak ( 2018-12-17 07:54:25 -0500 )edit

and really, why do python noobs NEVER check the ret value ?

berak gravatar imageberak ( 2018-12-17 07:55:11 -0500 )edit

@berak. The code above worked for me.

supra56 gravatar imagesupra56 ( 2018-12-17 09:44:45 -0500 )edit

@supra56, it also worked for me ;)

however, there may be combinations of hardware, drivers, etc, where it is not so...

berak gravatar imageberak ( 2018-12-17 09:47:25 -0500 )edit

The ret is boolean returned true.

supra56 gravatar imagesupra56 ( 2018-12-17 09:48:21 -0500 )edit

If you use windows 10 try to change privacy settings

LBerger gravatar imageLBerger ( 2018-12-17 11:34:52 -0500 )edit