OpenCV VideoCapture.isOpened() always returns False?

Question

I followed the installation tutorial at https://www.pyimagesearch.com/2017/09/04/raspbian-stretch-install-opencv-3-python-on-your-raspberry-pi/#comment-451314 , and everything installed fine.

But I can't actually get opencv to work at all.

>>> import cv2
>>> cap = cv2.VideoCapture(0)
>>> cap.isOpened()
False

Any attempt to capture video or images with cv2 basically doesn't work. I don't even know where to look for logs. Can anyone tell me where to start looking?

EDIT: I'm using the Raspberry Pi camera module, which apparently needs additional drivers or something. I'll post a solution if I find one, but in the meantime I'm still listening!

Answer 1

I was getting the same error while using opencv in anaconda3 virtual environment. I checked the buildinformation (cv2.getBuildInformation()) for current opencv version and ffmpeg wasn't marked "yes". To resolve this

1. I uninstalled opencv from my conda environment ( conda uninstall opencv)

2. Installed latest ffmpeg using conda-forge channel

3. Then installed opencv again using conda-forge channel ( conda install -c conda-forge opencv) . Don't install using menpo channel

Doing this resolved the issue for me.