Well, assuming the likes of
kdenlive don't match your requirements (which would probably be my general-purpose video editing suggestion), maybe you should look at the video editor in
blender. It has a node-based compositor, which can be used for tasks such as chroma key, or filtering video streams.
The problem about blender's VSE (video sequence editor) seems to be getting good information about it... I found this introduction on the wiki:
http://wiki.blender.org/index.php/Ma...quence_Editing
but it's little more than a statement that the VSE exists.
Blender is of course a whole lot more than just a video editor, but you don't have to use all the 3d modelling stuff to use the video editor.