This is more of a proof of concept than a fully functional web-application. Right now it allows you to load videos into the browser, they get automatically uploaded via WebsSocket to a node.js application, where those assets get transcoded (H264/WebM/OGG). Then you can create a composition (=new video), copy videos to the stage, trim them, transform them, stack them and then finally encode them on the server-side using AviSynth and ffmpeg Currently each encoding job will produce a H264 encoded video.
For the application you will need the following on the server-side (where the node-app is running):
Feel free to modify, contribute, fork, print it or whatever. Every part of this code I wrote is released under the WTFPL. For the libraries/modules I used you have to see for yourself.