@casm: many thanks for the links, that was very helpful.
I still have some questions regarding the VBI data. I am not a expert, but i assume it is something like the copyprotection from a VHS, just complete different data and no copyprotection. I dont know, but wouldnt it be enough, to capture the stuff with underscan enabled from a broadcast monitor, so that you have the "whole" frame? Capturing with a good card like a Blackmagic in lossless format?