How to stop the execution of the program after some time?

Question

Python

I want to authorize by face (through a webcam), but if the face was not found within, for example, 10 seconds, then the program issued a corresponding message and completed the face search, that is, returning to the authorization window.

1. How to display this window after 10 seconds?
Now 10 seconds pass and a window appears simultaneously with an error:

QObject::setParent: Cannot set parent, new parent is in a different thread

2. Как получить доступ к переменной cam из FaceUnlock в NoFace, чтобы завершить работу программы(поиска лиц) спустя 10 секунд?
Или может быть можно вызвать cam.release спустя 10 секунд в FaceUnlock? Только time.sleep останавливает программу, а мне нужно, чтобы без остановок, а с многопоточностью не получается пока что.
from threading import Timer

def FACE_UNLOCK(self):

        recognizer = cv2.face.LBPHFaceRecognizer_create()
        recognizer.read('trainer/trainer.yml')
        cascadePath = "haarcascade_frontalface_default.xml"
        faceCascade = cv2.CascadeClassifier(cascadePath);

        font = cv2.FONT_HERSHEY_SIMPLEX

#iniciate id counter
        id = 0

        face_un = ['Admin']

        cam = cv2.VideoCapture(0)

        w1 = cam.get(cv2.CAP_PROP_FRAME_WIDTH)
        h1 = cam.get(cv2.CAP_PROP_FRAME_HEIGHT)
  
    
# Define min window size to be recognized as a face
        minW = 0.1*w1
        minH = 0.1*h1 

        Timer(10, self.NoFace).start() #функция таймера на 10 секунд

        while(cam.isOpened()):

            ret, img =cam.read()    

            gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
            faces = faceCascade.detectMultiScale( 
                gray,
                scaleFactor = 1.2,
                minNeighbors = 5,
                minSize = (int(minW), int(minH)),
                )
        

            for(x,y,w,h) in faces:

                cv2.rectangle(img, (x,y), (x+w,y+h), (0,255,0), 2)

                id, confidence = recognizer.predict(gray[y:y+h,x:x+w])

            # Check if confidence is less them 100 ==> "0" is perfect match 
                if (confidence < 100):
                    id = face_un[0]
                    confidence = "  {0}%".format(round(100 - confidence))
                    cam.release()
                    self.FProj = ProjectPrg()
                    self.FProj.show()
                    Main.setVisible(self, False)
     
                else:
                    id = "unknown"
                    confidence = "  {0}%".format(round(100 - confidence))

                cv2.putText(img, str(id), (x+5,y-5), font, 1, (255,255,255), 2)
                cv2.putText(img, str(confidence), (x+5,y+h-5), font, 1, (255,255,0), 1) 
            cv2.imshow('Face Unlock',img) 
            k = cv2.waitKey(10) & 0xff # Press 'ESC' for exiting video
            if k == 27:
                break         
              
        cam.release()
        cv2.destroyAllWindows()

def NoFace(self):
        msg1 = QMessageBox(self)
        msg1.about(self, "Ошибка", "Программа не обнаружила лицо администратора.\nВ авторизации по лицу отказано, используйте пароль и логин.")

Answer 1

Just add a timeout parameter to FACE_UNLOCK(), capture the current time before entering the while(cam.isOpened()) loop, and inside the loop check if enough time has elapsed or not.