artoolkit no webcam showing

[vrmdl]

Hi, all

I tried to get artookit example running on my PC. I tried to run the artoolkit_simple that came with the vizard. Codes are shown below.

*************
import viz
viz.go()

#Add ARToolkit extension
ar = viz.add('artoolkit.dle')

#Create camera using first available webcam
camera = ar.addWebCamera()

#Create marker from pattern file
marker = camera.addMarker('ar/patt.worldviz',width=1000)

#Add logo model
logo = viz.add('logo.ive')

#Link logo model to marker sensor
viz.link(marker,logo)
*************

However the screen shows nothing only black/white dots (see screenshot). It looks like the webcam is not turned on. However I checked my webcam setting. My webcam shows fine in programs such as skype.

The message window shows no error but the following

************************************************** ****************************
** Loading artoolkit_simple.py
************************************************** ****************************
artoolkit.dle ARToolkit Extension
VideoCamera.dle Video Camera Extension
** WARNING: Video camera does not support capturing at 640 x 480, using default size (720 x 576)
** NOTIFY: Connected to 'AVerMedia 7231 Analog Capture' (720 x 576 , 25.00 fps)
Loading File: logo.ive
** Load Time: 0.55 seconds

Any help or hint is helpful.