streamdev-server (vdr plugin) already does it for live tv: if you use the url, e.g., http://vdr:3000/Extern/5, it will pipe channel 5 to an external remuxer of your choice (usually a script to call mencoder with suitable parameters) and stream it to you.
Note that you can also open in a browser http://vdr:3000/Extern/channels.html and you'll get a clickable list of channels.
What's missing (or maybe it already exists, I don't know) is a plugin to convert vdr epg to xmltv (and in a suitable format for videocenter) and a solution for recordings.