Thanks for the links Adonay.
It seems that Natron is more for post production and special FX than editing.
I had a look at OpenShot but can really tell if it's more stable than Pitivi
already installed in Trisquel.
It seems really basic. It seems to be good software for people who have to
make a video editing quickly without having the time to understand how it
works.
But comparing to Pitivi, I like when Pitivi is asking first what is your
project (sreen size, frames per minutes)
Both on Trisquel 6 & 7, I always have an unstable Pitivi. I always have to
save my project or restart it because I can't do anything or Pitivi have bugs
in showing my edition.
But I always had correct out renderings.
Blender doesn't support to work with ogg formats. You have to transfer into
mp4 before. But it does a great job in editing !
Kdenlive seems to be a good compromise between OpenShot/Pitivi and Blender
for usual editing (you tube, mediagoblin) but limits the video and audio
tracks. Seems really easy to use.