I created my first addon which converts and archives vdr recordings as mp4 video files and put it on github:
The addon only supports linux as it will convert locally stored vdr recordings. It's still in beta status but I've tested it on my Ubuntu 16.04 and believe it is safe to use. If you don't tick the option to delete the source files after conversion it should do no harm and only create the mp4 file in the destination folder.
Maybe some of you will also find it useful.
If you like to test I'd be happy to receive your feedback.