Opus, the royalty-free lossy audio codec designed for real-time applications on the web, has a native decoder implemented within the FFmpeg-forked Libav project. Added to libavcodec was nearly six thousand lines of new code to bundle a native Opus decoder within the code-base. The initial Opus work was developed by a student during Google Summer of Code 2012, then completed by a project sponsored by Mozilla, and then further enhanced by other open-source developers.
The Libav Opus decoder landed late last night with this Git commit. Previously both Libav and FFmpeg have offered Opus encode/decode support but it's been dependent upon the external libopus library.
The Opus audio format is used by various VoIP programs, is mandated for WebRTC usage, can be used with various streaming audio programs, etc.