ffmpeg invisible watermarking (libavfilter filter) by Joust

I need a good ffmpeg or c/c++ hacker that can fix me an ffmpeg filter – libavfilter API. These are the filters that are invoked using “-vfilter” param. The api is open and quite well documented. There is a number of sample filters with code… (Budget: $30-250, Jobs: Algorithm, C Programming, Cryptography, Linux, Video Services)