An increasing number of ports need ffmpeg's libavcodec. This increase is welcome and should be encouraged over the usage of bundled versions of libavcodec.
However, ffmpeg itself depends (optionally) on some of these ports, which creates CIRCULAR dependencies.
We should create a separate multimedia/libavcodec with all of those -- such as libsoxr and chromaprint, and the rest of ffmpeg -- depending on it.
Until the ports framework gains support for creating multiple packages from a single port without rebuild splitting the port into many parts is likely to require slaves or flavors. And without patches maintenance is unknown.