Written by Ronald Bultje and Clément Bœsch, the decoder is built around FFmpeg and has been written from scratch. The pair say that FFmpeg aims to be a fast, free, community-developed implementation similar to ffvp8. The sorts of speeds being talked about are between 25 and 50 per cent faster than the libvpx-based decoder and there is significant improvements too in multi-threaded performance.
The developers wrote a FFmpeg's VP8 decoder which was also faster than Google's own VP8 video decoder. But all of this is decoder-only, and the big issue for VP9 adoption - at this point - is encoder performance, so while it is all well and good it is going to be a while before any of this makes much of an impact.