CODEWITHSUNDEEP
pythonpython-3.xopencvubuntuvideo-capture
Nabeel Ayub
Nabeel Ayub

Reputation: 1250

OpenCv error can't open camera through video capture

I was using my cam through opencv and suddenly after restarting I ran my code it shows below error:

[ WARN:0] global /io/opencv/modules/videoio/src/cap_v4l.cpp (802) open VIDEOIO ERROR: V4L: can't open camera by index 0
Traceback (most recent call last):
  File "test.py", line 20, in <module>
    retval, buffer_img = cv2.imencode('.jpg', frame)
cv2.error: OpenCV(4.1.2) /io/opencv/modules/imgcodecs/src/loadsave.cpp:877: error: (-215:Assertion failed) !image.empty() in function 'imencode'

cap = cv2.VideoCapture(0)  # here it throws an error


import json
while(True):
    # Capture frame-by-frame
    ret, frame = cap.read()

    retval, buffer_img = cv2.imencode('.jpg', frame)

    resdata = base64.b64encode(buffer_img)

    resdata = "data:image/png;base64,"+ str(resdata.decode("utf-8"))
    PARAMS = {'image': resdata}

    # Our operations on the frame come here
    #gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)

    # Display the resulting frame
    cv2.imshow('frame',frame)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()

I also tried with cap = cv2.VideoCapture(1) but then it shows can't find camera

How can I fix this issue?

Upvotes: 43

Views: 177085

Answers (21)

Mohammad Hosein Abedi
Mohammad Hosein Abedi

Reputation: 40

I had a problem like you, in my case i closed the cammera with cap.release() immediately after capturing frames

Upvotes: 0

John Howell
John Howell

Reputation: 1

This solution is for Mac only.

  1. I used PyCharm rather than Anaconda. I couldn't figure out how to get Mac system to recognize the camera on Anaconda, but PyCharm, after running the code will ask for permission. Also, the opencv version for Anaconda is out of date and doesn't have some of the features of PyCharm.

  2. Under System Settings, Privacy and Security, Camera make sure the camera is enabled for PyCharm.

  3. The HD FaceTime camera is cap=cv2.VideoCapture(2) not (0). You will find that cv2.VideoCapture(0).isOpened() is True, but the ret, image=cap.read() will return ret as False if it is the wrong camera.

  4. if it is still not working, try adding this:

cap = cv2.VideoCapture(2)  
cap.release()   
cap= cv2.VideoCapture(2)

It could be that you have an open window that the program believes is opened.

Upvotes: 0

Enos jeba
Enos jeba

Reputation: 132

cap = cv2.VideoCapture(0)

The 0, 1, 2, etc digit we pass through the VideoCapture function is the device index given to the device from the os. As the device index is assigned by os, The number would be at random. So to find out the device index of your camera, in linux open command line

sudo apt-get install v4l-utils

Once installed use

v4l2-ctl --list-devices

to list all connected device something like this

Integrated Camera (usb-0000:00:3b.0-1.2):
    /dev/video0

Upvotes: 2

Miles
Miles

Reputation: 1

The solution that worked for me as other contributors noted was to simply unplug the camera from the USB port and plug it back in, while the Raspberry PI Ubuntu OS was running.

Upvotes: 0

Anamika Gupta
Anamika Gupta

Reputation: 81

video = cv2.VideoCapture(0,cv2.CAP_DSHOW)

This worked for me.

Upvotes: 5

Adri&#225;n &#193;lvarez
Adri&#225;n &#193;lvarez

Reputation: 1

Don't know if this is still an issue. In my case, I was getting the same error until I unplugged and plugged the usb camera. Even if I reboot, the error happened.

It's similar to someone said: my camera was already been captured. The problem is that it was not used by my script, so it was hard to identify.

A few days before the issue, I installed the motion library, but just to test something and I didn't use it anymore. The motion starts at boot, so the camera was being captured by the service. That's why only the unplug-plug worked.

I uninstalled the library, and the error was gone.

Upvotes: 0

Du Nguyễn Phan
Du Nguyễn Phan

Reputation: 79

I have do everytime after restart or unplug usb camera and replug

chmod 777 /dev/video0

Upvotes: 0

X.Liu
X.Liu

Reputation: 11

Tried every anwser but only changing camera id from -1 to 1 and then back to 0 worked.

Upvotes: 1

Diego
Diego

Reputation: 43

I found a solution in https://github.com/opencv/opencv/issues/19527 where the video capture is inside the function instead of outside. That worked for me (ubuntu)

def frame_generation():

camera = cv2.VideoCapture(0) #resolved, correct position

while(True):

Upvotes: 4

Anthony Tomasic
Anthony Tomasic

Reputation: 193

The OP appears to be operating on a Raspberry PI. Raspberry is moving to a new system to manage cameras, so when the user upgrades the OS via sudo apt-get upgrade the camera system gets the new library and the legacy camera system is disabled. To enable the legacy camera system again, try

sudo raspi-config

Then select

3 Interface Options    Configure connections to peripherals

then select

I1 Legacy Camera Enable/disable legacy camera support

and follow the directions to enable and then reboot.

Of course, this patch will only work for so long, as the legacy system has been deprecated.

Upvotes: 2

TOPworkOUT
TOPworkOUT

Reputation: 19

I've also had this problem on Ubuntu

I've solved this by these comands

sudo adduser username video sudo usermod -a -G video username

username - it is the name of your device

than write

id -a

and copy index from ()

for me it is 1000

so than just write:

camera = cv2.VideoCapture(1000)

Upvotes: 1

Gardinal
Gardinal

Reputation: 112

For Linux, make sure OpenCV is built using the WITH_V4L (with video for linux).

Upvotes: 1

Vibhanshu Jain
Vibhanshu Jain

Reputation: 21

I also had the same problem. Just changed it to 1 and it was perfectly working. I guess it's related to the number of camera devices you have used.

For example, I guess I have Iruin external camera as my first option which I didn't connect this time.

Here is the error and corrected code.

global /tmp/pip-req-build-f51eratu/opencv/modules/videoio/src/cap_v4l.cpp (890) open VIDEOIO(V4L2:/dev/video0): can't open camera by index

Code to change:

vid = cv2.VideoCapture(1)

Upvotes: 2

chilin
chilin

Reputation: 416

I've encountered the same issue and attempted several methods like cv2.VideoCapture(-1) or cv2.VideoCapture(1) but without much success.

I succeeded after reading this article and disabling debug-mode

Upvotes: 2

129lovely
129lovely

Reputation: 19

In my case, I just reconnected cam to the usb port, and then it was solved! I think this error is caused by closing the window in the wrong way. Please check if there is any exception on the terminal right after closing the window.

Upvotes: 1

Amine Sehaba
Amine Sehaba

Reputation: 120

This issue is due to the interruption. Try to end the execution with the key 'q' for example, don't close the window suddenly.

I solved the same issue by opening terminal again and execute the same script again.

Upvotes: -1

Mazhai
Mazhai

Reputation: 191

Most likely a permission issue on /dev/video0.

Check if you are part of "video" group.
id -a

if you don't see video in your group list add sudo usermod -a -G video

for Ubuntu users:(20.04)
sudo usermod -a -G video $LOGNAME

Logout and log back in and try it.

Upvotes: 19

abey
abey

Reputation: 267

I got the same error. Try changing 0 to -1

cap = cv2.VideoCapture(-1)

This solved the issue.

Upvotes: 25

ankit
ankit

Reputation: 394

I got the same problem when I created more than one instance of the cv2.VideoCapture(0). So check if your code contains multiple initializations or sections which call cv2.VideoCapture(0) more than once. I was facing this problem while running the flask server in debug mode because it called cv2.VideoCapture(0) twice.

import cv2
cap = cv2.VideoCapture(0)
cap2 = 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()

Error:

python3 debugCamera.py 
[ WARN:0] global /io/opencv/modules/videoio/src/cap_v4l.cpp (887) open VIDEOIO(V4L2:/dev/video0): can't open camera by index

Upvotes: 21

veradeus
veradeus

Reputation: 61

I had the same problem, Just change 0 to 1,then to -1 and back again to 0. Don't know why this worked for me.

Upvotes: 6

Sohel Reza
Sohel Reza

Reputation: 321

I will not go to that part What you are trying to do, here is just a block of code that can open your camera every time you run it,

python: 3.7.3

OpenCV: 4.1.0

import cv2
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()

Upvotes: 2

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