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When I run my nooby opencv program on python using macbook air it does not show anything. Also the program exits after 0.5-1 second.

Here is the code, it is really pretty simple

import cv2



cap = cv2.VideoCapture(0)
cap.set(3,640)
cap.set(4,480)

while True:
     success, img = cap.read()
     cv2.imshow("Video", img)

     if cv2.waitKey(1) & 0xFF == ord('q'):
         break
Dias Mashikov
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1 Answers1

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You should first list the available camera ids

Here you can use G M's answer:

def list_ports():
    is_working = True
    dev_port = 0
    working_ports = []
    available_ports = []
    while is_working:
        camera = cv2.VideoCapture(dev_port)
        if not camera.isOpened():
            is_working = False
            print("Port %s is not working." % dev_port)
        else:
            is_reading, img = camera.read()
            w = camera.get(3)
            h = camera.get(4)
            if is_reading:
                print("Port %s is working and reads images (%s x %s)" % (dev_port, h, w))
                working_ports.append(dev_port)
            else:
                print("Port %s for camera ( %s x %s) is present but does not reads." % (dev_port, h, w))
                available_ports.append(dev_port)
        dev_port += 1
    return available_ports, working_ports

Result will be:

Port 0 is working and reads images (720.0 x 1280.0)
OpenCV: out device of bound (0-0): 1
OpenCV: camera failed to properly initialize!
Port 1 is not working.

For instance, for my mac, camera id (cid) 0 is available but not 1.

Therefore I initialized the code with cid 0.

cap = cv2.VideoCapture(0)
cap.set(3, 640)
cap.set(4, 480)
while cap.isOpened():
    success, img = cap.read()

    if success:
        cv2.imshow("Video", img)
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break

You should not initialize VideoCapture object by default 0. Since it may not work. If there is no available port listed as a result, you may need an external camera.

Ahmet
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