save video using opencv

# Python program to illustrate  
# saving an operated video 
  
# organize imports 
import numpy as np 
import cv2 
  
# This will return video from the first webcam on your computer. 
cap = cv2.VideoCapture(0)   
  
# Define the codec and create VideoWriter object 
fourcc = cv2.VideoWriter_fourcc(*'MJPG') 
out = cv2.VideoWriter('output.avi', fourcc, 20.0, (640, 480)) # Make sure (width,height) is the shape of input frame from video
# use print(frame.shape) if required to check its size
# loop runs if capturing has been initialized.  
while(True): 
    # reads frames from a camera  
    # ret checks return at each frame 
    ret, frame = cap.read()  
  
    # Converts to HSV color space, OCV reads colors as BGR 
    # frame is converted to hsv 
    hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV) 
    # output the frame 
    out.write(hsv) 
      
    # The original input frame is shown in the window  
    cv2.imshow('Original', frame) 
  
    # The window showing the operated video stream  
    cv2.imshow('frame', hsv) 
  
      
    # Wait for 'a' key to stop the program  
    if cv2.waitKey(1) & 0xFF == ord('a'): 
        break
  
# Close the window / Release webcam 
cap.release() 
  
# After we release our webcam, we also release the output 
out.release()  
  
# De-allocate any associated memory usage  
cv2.destroyAllWindows()