Video recorded from screen using opencv, pyautogui and numpy is faster than the original or slower

Question

I've tried to write a program on python that should record the screen. But I faced with a problem that output is faster than original. I tried to change fps value or making a delay in frame recording but it hasn't help. Please, help me. There is my code below

import pyautogui
import cv2
import numpy as np

resolution = (1920, 1080)

codec = cv2.VideoWriter_fourcc(*"XVID")
filename = "Recording.avi"

fps = 20.0
out = cv2.VideoWriter(filename, codec, fps, resolution)
cv2.namedWindow("Live", cv2.WINDOW_NORMAL)
cv2.resizeWindow("Live", 480, 270)

while True:
    img = pyautogui.screenshot()
    frame = np.array(img)
    frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
    out.write(frame)
    cv2.imshow('Live', frame)

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

out.release()
cv2.destroyAllWindows()