Webcam + Open CV Python | Black screen

Question

I am using the code below, but I get a black image. Could you please help me rectify the error?

import cv2
import numpy as np
c = cv2.VideoCapture(0)

while(1):
    _,f = c.read()
    cv2.imshow('e2',f)
    if cv2.waitKey(5)==27:
        break
cv2.destroyAllWindows()

Solution 1

Update: See github.com/opencv/opencv/pull/11880 and linked conversations, only few backends support -1 as index.

---

Although this is an old post, this answer can help people who are still facing the same problem. If you have a single webcam but it renders all black, use cv2.VideoCapture(-1). This will get you the working camera.

Solution 2

Just change cv2.waitKey(0) to cv2.waitKey(30) and this issue will be resolved.

Solution 3

I've faced with same problem. Updating neither opencv nor webcam driver works. I am using kaspersky as antivirus. When I disable the kaspersky, then black output problem solved.

BTW, I can see the running .py file in kaspersky console > reports > host intrusion prevention. It reports application privilege control rule triggered - application: myfile.py, result: blocked: access to video capturing devices

Solution 4

Try this:

import cv2
import numpy as np

cap = cv2.VideoCapture(0)

while(True):
    ret, frame = cap.read()

    cv2.imshow('frame',frame)

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

View more solutions

Comments

[rayryeng]

possible duplicate of Using webcam with opencv python shows a black screen w/waitkey()

[berak]

please check c.isOpened()

[M Umair]

reinstalling OpenCV module fixed the problem for me.

[rayryeng]

Not sure if that will help. I think it has something to do with the webcam itself.

[Aphire]

Hah yeah just noticed that as I posted.

[Aphire]

Well hopefully OP will update with more system info. then someone more hardware orientated will be able to assist.

[rayryeng]

lol no worries. BTW, this is better code than the OP has posted. It's more robust. The variable names in the original code are just awful.

[thsieh]

This happens to me after continuously running the capture a couple hours. No matter it is logitech or other brands. After went black, I run this cv2/VideoCapture(-1) and it comes back to life. Wonder if @praveen you know whats the reason and how this helped? And what this is different from cv2.release()

[Praveen]

Just realized that only few backends support the use of '-1' to search for the first available/free camera. See github.com/opencv/opencv/pull/11880 and linked conversations.

[OscarSan]

Thanks, I disable Kaspersky and it worked like a charm