Why this error in cvtColor function happens?

edit

Why I have error in python script? I have python 2.6.6 installed on Centos 6.4 x64

 [root@--- ~]# python test.py 1.mp4
    OpenCV Error: Assertion failed (scn == 3 || scn == 4) in cvtColor, file /root/opencv-2.4.4/modules/imgproc/src/color.cpp, line 3326
    Traceback (most recent call last):
      File "test.py", line 231, in <module>
        print process(fileName)
      File "test.py", line 198, in process
        detector = Detector(frame)
      File "test.py", line 127, in __init__
        self._initAvg(frame)
      File "test.py", line 171, in _initAvg
        f = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    cv2.error: /root/opencv-2.4.4/modules/imgproc/src/color.cpp:3326: error: (-215) scn == 3 || scn == 4 in function cvtColor

link to 1.mp4

link on my script