OpenCV Returning error message when webcam is not connected

Question

I am using OpenCV 3.3 with Python 2.7 on a Windows 10 PC. In one of my projects, I am connecting an external webcam to do some tracking. Everything works well as long as the webcam is connected. If the webcam is disconnected before the program runs/during the program, the program crashes. When I tried a dummy program to check what's going wrong, I noticed that the program crashes in the line where i call cv2.VideoCapture(0) itself.

Code Snippet:

cap=cv2.VideoCapture(0) -- this line is in the main program and if camera is not connected, the program crashes at this point

--The below lines are inside a function and is called by the main program based on some other input

r, a = cap.read()

while not r:

print 'Reconnect Camera'

r , a = cap.read()

print 'All Okay!'

I put the while loop in there to prevent problems if the camera is disconnected after the cap=cv2.VideoCapture(0) but before cap.read() inside the function. This also does not do the work as 'r' value becomes true in the second iteration even after the camera disconnects. I have put a graph below to represent the behavior of 'r' with camera's connection.

a -> Camera is disconnected and 'r' goes to false;b -> Camera is still disconnected but 'r' is true now;c-> Camera is re-connected and 'r' goes to false;d -> Camera is connected, 'r' goes back to true but

I might be doing something wrong! How do I fix this?! Thanks in advance guys!

LucasRT LucasRT · Accepted Answer · 2017-11-08T21:36:17

first you need to have at least one camera pluged, without any camera the program have to fail. cv2.VideoCapture(0) is looking for the first camera (number cero), so if you plug the camera out will return error. how to fix: list cameras, set the one that´s not the webcam as default

OpenCV Returning error message when webcam is not connected

1 Answers