For Kdenlive on Trisquel, the video player does not work for editing video (however I can capture video from my webcam).

I think it may have to do with xv not being present:

http://trisquel.info/en/wiki/software-d ... ines#toc94

xv the image viewer program? I don't think that is the problem. I don't think that is installed on my ubuntu but I have kdenlive running.

How did you install?

You have a few options - https://userbase.kde.org/Kdenlive/Manual/Installation

Thanks, I found the problem, on Trisquel the video player is not shown by default (like Ubuntu), however a video capture pane is.