wiiaboo scolded me, I was wrong where I mentioned ideas about adding features for xvid. This repo only exists for convenience to load xvid sources from using git instead of SVN, to build them in MABS. It is not an active fork for further development.
So if you want to contribute to xvid, you may have to register as xvid developer in their organization to obtain commit rights to their main SVN repo, or discuss contributions in their developer mailing list.