[python] face detection from video file

#! /usr/bin/python

import cv2

face_cascade = cv2.CascadeClassifier('lbpcascade_frontalface.xml')

vc = cv2.VideoCapture('video.mp4')

if vc.isOpened():

    rval , frame = vc.read()

else:

    rval = False

roi = [0,0,0,0]

while rval:

    rval, frame = vc.read()

    # resize frame for speed.

    frame = cv2.resize(frame, (300,200))

    # face detection.

    faces = face_cascade.detectMultiScale(frame, 1.8, 2)

    nfaces = 0

    for (x,y,w,h) in faces:

        cv2.rectangle(frame,(x,y),(x+w,y+h),(0,0,255),2)

        nfaces = nfaces + 1

        roi = [x,y,w,h]

    # undetected face, show old on position.        

    if nfaces == 0:

        cv2.rectangle(frame,(roi[0],roi[1]),(roi[0]+roi[2],roi[1]+roi[3]),(0,0,255),2)

    # show result

    cv2.imshow("Result",frame)

    cv2.waitKey(1);

vc.release()