How to pause and resume threads in pyqt?

Hi, I have a pyqt app that I get frames from a camera (not webcam it has its own library) and process frames then put frames into a big numpy array to make a big image, so I have a worker thread that does all processes and shows live frames and thumbnail and ROIs in gui using signals and slots, inside run function of worker thread I have multiple while loops that are needed for my processes, how can I add a pause and resume functionality to it?
also I added another worker thread to my app to handle saving and converting operations of big image but when I click those buttons GUI gets stuck for a second then it comes responding is there anything I should do to make it realtime and not stuck for a second or its how it should work?