I just noticed quvi supports playing back YouTube in WebM format and some
other sites via MPlayer. All one needs to do is install quvi (compilation
instructions for versions newer than those in the Trisquel repositories can
be found here:
http://quvi.sourceforge.net/doc/other/howto-compile-linux.html), MPlayer and
add to the MPlayer config file (in .mplayer/config) something like this:
quvi-format=default
cache-min=30
cache=8192
(I selected default since otherwise it opens highest quality video, e.g.
1080P).
A list of supported sites can be found by running the command
quvi --support
I tested YouTube, videobash, liveleak, theonion and flix.tapuz (Hebrew site)
and they work. Some Dailymotion videos work also (but others do not).
Then simply playback video using
mplayer URL
or (for better quality)
mplayer --quvi-format=best URL
