snipplets.dev/code/Python/opencv/capture.py

#!/usr/bin/env python3

import cv2

RTSP_ADDR = 'rtsp://localhost:8554/cam'
DEVICE_ADDR = 2

cam = cv2.VideoCapture(DEVICE_ADDR)

while True:
    result, image = cam.read()

    cv2.imshow('Camera', image)

    if cv2.waitKey(1) & 0xFF == ord('s'):
        cv2.imwrite('capture.png', image)

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

cam.release()

cv2.destroyWindow('Camera')
cv2.destroyAllWindows()