# Open video file
cap = cv2.VideoCapture(video_path)

# Define the codec and create VideoWriter object
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter(output_path, fourcc, 20.0, (640, 480))

while cap.isOpened():
    ret, frame = cap.read()
    if not ret:
        break
    
    # Convert frame to grayscale for detection
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    
    # Detect dogs in the frame
    dogs = dog_cascade.detectMultiScale(gray, scaleFactor=1.1, minNeighbors=5, minSize=(30, 30))
    
    # Draw rectangles around the detected dogs
    for (x, y, w, h) in dogs:
        cv2.rectangle(frame, (x, y), (x+w, y+h), (255, 0, 0), 2)
    
    # Write the frame into the file 'output.avi'
    out.write(frame)
    
    # Display the resulting frame
    cv2.imshow('frame', frame)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

# Release everything when finished
cap.release()
out.release()
cv2.destroyAllWindows()