Access webcam using OpenCV (Python) in Docker?

user_2315046 0
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I'm trying to use Docker for one of our projects which uses OpenCV to process webcam feed (Python). But I can't seem to get access to the webcam within docker, here's the code which I use to test webcam access:

python -c "import cv2;print(cv2.VideoCapture(0).isOpened())"

And here's what I tried so far,

 docker run --device=/dev/video0 -it rec bash

 docker run --privileged --device=/dev/video0 -it rec bash

 sudo docker run --privileged --device=/dev/video0:/dev/video0 -it rec bash

All of these return False, what am I doing wrong?

docker opencv python
4 Answers

Try to use this:

-v /dev/video0:/dev/video0

in place of 

--device=/dev/video0

and execute:

$ xhost +

before docker run

user_24843880

The easisest way I found to have a dockerized OpenCV able to connect to your webcam is by using the following Dockerfile :

FROM ubuntu:20.04

ENV TERM=xterm
ENV DEBIAN_FRONTEND=noninteractive

RUN apt-get update && apt-get install -y --no-install-recommends \
    libopencv-dev \
    python3-opencv \
    && apt-get clean \
    && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*

WORKDIR /app
ADD . /app

ENV PYTHONUNBUFFERED=1
ENV PYTHONPATH=/app

and then build it and run in this way :

docker build -t opencv-webcam .
docker run -it -v $PWD:/app/ --device=/dev/video0:/dev/video0 -v /tmp/.X11-unix:/tmp/.X11-unix -e DISPLAY=$DISPLAY opencv-webcam bash

and run the following script inside the container with python3 script.py:

import cv2


WINDOW_NAME = "Opencv Webcam"

def run():

    cv2.namedWindow(WINDOW_NAME)

    video_capture = cv2.VideoCapture(0)

    while True:
        ret, frame = video_capture.read()
        print(ret, frame.shape)

        cv2.imshow(WINDOW_NAME, frame)
        cv2.waitKey(1)

if __name__ == "__main__":
    run()
user_3172470

I ran into issues when using a non-privileged Dockerfile (i.e. with a USER line):

The container must be started with --user {UID} ; NOT --user {UID}:{GID} (same for user: line in docker-compose.yml! If the gid is set, weirdly this will not inherit the video group permission needed for access to the webcam files (/dev/video0 etc.). Also, the internal Dockerfile user must be added to the video group; add this after the USER line (and after installing sudo and adding the user to sudoers):

RUN sudo usermod -a -G video <InternalUsername>

Before you try theses steps: run everything in privileged mode to test if your problem lies really here.

user_3441590
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