VIDEOIO ERROR: Pixel Format is unsupported

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Ive been sucked for two days on this one. My application is to do QR-code scanning in real-time with opencv. So Im using SQ11 spy cameras with 'MPEG' video format (found out from 'v4l2-ctl --list-formats'). But strangely, I could take a photo with the camera, through v4l2-ctl -stream... (something I found on other forums).

I used this function: cap = cv2.VideoCapture(0)

Also, another error saying 'can't open camera by index 0' was printed followed by the error mentioned above. Am I calling the function wrongly? Or is there a way to verify the source?