So, this should become an alternative to libavcodec, which is mostly LGPL-licensed. It's a bad license, because it does not allow static linking.
The suitable licenses for the core library could maybe be extremely permissive, like zlib or CC0. The individual codecs can have a little more restrictive permissive licenses, such as BSD.
Well, there are already some permissive codecs: http://en.wikipedia.org/wiki/List_of_open_source_codecs
Video codecs (license):
Audio codecs (license):
Diff: