How to display output in more than one window with VLC Media Player.
September 2010.
To display output in more than one window, video cloning can be used. To use this, specify
--vout-filter=clone
on the command line: this tells vlc to use cloning. You also need to tell vlc what output modules you want with, for example,
--clone-vout-filter=caca,glx
--clone-count=2
Source: http://wiki.videolan.org/Video_Output