vid_proc.py

import numpy as np
import cv2

cap = cv2.VideoCapture(r'./input_file.mp4')

#OSX:
fourcc = cv2.cv.CV_FOURCC('m', 'p', '4', 'v')
vout = cv2.VideoWriter()
out_fps = 30.0
success = vout.open('output_file.mov',fourcc,out_fps,(720,1280),True)

canvas = None

while(cap.isOpened()):
    ret, frameraw = cap.read()

    if canvas == None:
        canvas = np.zeros(frameraw.shape, dtype='float32')

    frame = frameraw.astype('float32') / 256.0

    canvas = np.maximum(canvas*0.9, frame)

    #cv2.imshow('window',frame)
    cv2.imshow('window',canvas)
    vout.write(np.round(canvas * 256.0).astype('uint8'))

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

cap.release()
vout.release()
cv2.destroyAllWindows()