Unsolved Threads in Python and Qt

[iamMHZ]

i have a code in python ,
and it has 5 buttons ,
and when each button clicks i want to access the webcam ,
and get frames from it and do some things on the webcam frames(each button performs diffrient things on the webcam frame)

the problem is that when first button gets the webcam on a separate THREAD
when i click other buttons , they can't access the Webcam ,
how can i notify the that thread to releases the Webcam for others
?