For those who got tired of waiting, I've added here some docs on how to
cut a WebM video (like those of Wikimania 2012 on YouTube) in a few
seconds for Commons upload:
<https://commons.wikimedia.org/wiki/Help:Converting_video#WebM_with_mkvtoolnix>
(Other video editors all have peculiar idiosyncrasies which were
impossible to overcome for a newbie like me.)
Of course you first have to download:
http://rg3.github.com/youtube-dl/
Nemo