grey = cv2.cvtColor(frame1,cv2.COLOR_BGR2GRAY) cv2.error: OpenCV(4.1.2)

What happened Can you help?
thank you

Code

import cv2
import numpy as np
from time import sleep

largura_min=80 #Largura minima do retangulo
altura_min=80 #Altura minima do retangulo

offset=6 #Erro permitido entre pixel

pos_linha=550 #Posição da linha de contagem

delay= 60 #FPS do vídeo

detec = []
carros= 0

def pega_centro(x, y, w, h):
x1 = int(w / 2)
y1 = int(h / 2)
cx = x + x1
cy = y + y1
return cx,cy

cap = cv2.VideoCapture('11.mp4')
subtracao = cv2.bgsegm.createBackgroundSubtractorMOG()

while True:
ret , frame1 = cap.read()
tempo = float(1/delay)
sleep(tempo)
grey = cv2.cvtColor(frame1,cv2.COLOR_BGR2GRAY)
blur = cv2.GaussianBlur(grey,(3,3),5)
img_sub = subtracao.apply(blur)
dilat = cv2.dilate(img_sub,np.ones((5,5)))
kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (5, 5))
dilatada = cv2.morphologyEx (dilat, cv2. MORPH_CLOSE , kernel)
dilatada = cv2.morphologyEx (dilatada, cv2. MORPH_CLOSE , kernel)

img,contorno,h = cv2.findContours(dilatada,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)
cv2.line(frame1, (25, pos_linha), (1200, pos_linha), (255,127,0), 3) 
for(i,c) in enumerate(contorno):
    (x,y,w,h) = cv2.boundingRect(c)
    validar_contorno = (w >= largura_min) and (h >= altura_min)
    if not validar_contorno:
        continue

    cv2.rectangle(frame1,(x,y),(x+w,y+h),(0,255,0),2)        
    centro = pega_centro(x, y, w, h)
    detec.append(centro)
    cv2.circle(frame1, centro, 4, (0, 0,255), -1)

    for (x,y) in detec:
        if y<(pos_linha+offset) and y>(pos_linha-offset):
            carros+=1
            cv2.line(frame1, (25, pos_linha), (1200, pos_linha), (0,127,255), 3)  
            detec.remove((x,y))
            print("Carros detectados  o momento: "+str(carros))        
   
cv2.putText(frame1, "VEICULOS: "+str(carros), (450, 70), cv2.FONT_HERSHEY_SIMPLEX, 2, (0, 0, 255),5)
cv2.imshow("Video Original" , frame1)
cv2.imshow("Detectar",dilatada)

if cv2.waitKey(1) == 27:
    break

cv2.destroyAllWindows()
cap.release()

No repository file, test, or project entry point is identified; start by reproducing the pasted Python snippet and inspecting the full OpenCV traceback around cv2.cvtColor(frame1, cv2.COLOR_BGR2GRAY). Done would require a clearly scoped, reproducible issue tied to this repository, with the expected behavior and a verified fix or explanation.