How do you plan on distributed processing using
libavformat? It's a very efficient, low level C-based encoder/decoder library, but it's never been targeted towards distributed coding.
Because that would mean it'd have to implement network communication protocols, etc. and that isn't really in the spirit of such a library. It'd be too much overhead.
This is not to say that somebody could write a middleware software that would bundle and synchronize multiple libav installations on distributed machines, but I doubt there is a thing like that.
On the other hand, in the professional league, there are alternatives. On OS X for example, there is the combination of Compressor and Qmaster, which are made for that purpose:
Compressor 2 can accelerate processing by distributing the work to multiple computers. All you need is access to more than one computer and Compressor 2 installed with either DVD Studio Pro 4 or Final Cut Studio
One can also use Qmaster for any other Unix command line program. At the moment I can't recall a Windows alternative for that, but there surely are some.