plugin=diff is not implemented.
http://yellow.ribbon.to/~tuotehhou/index.php?%2BOpencv%2BOpenCV%E3%81%AELinux%E3%83%A9%E3%82%A4%E3%83%96%E3%83%A9%E3%83%AA%E3%82%92%E3%82%B3%E3%83%B3%E3%83%91%E3%82%A4%E3%83%AB
plugin=diff is not implemented.