%% You should probably cite rfc6716 instead of this I-D.
@techreport{ietf-codec-opus-13,
    number =    {draft-ietf-codec-opus-13},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-ietf-codec-opus/13/},
    author =    {Jean-Marc Valin and Koen Vos and Timothy B. Terriberry},
    title =     {{Definition of the Opus Audio Codec}},
    pagetotal = 329,
    year =      2012,
    month =     may,
    day =       16,
    abstract =  {This document defines the Opus interactive speech and audio codec. Opus is designed to handle a wide range of interactive audio applications, including Voice over IP, videoconferencing, in-game chat, and even live, distributed music performances. It scales from low bitrate narrowband speech at 6 kb/s to very high quality stereo music at 510 kb/s. Opus uses both linear prediction (LP) and the Modified Discrete Cosine Transform (MDCT) to achieve good compression of both speech and music.},
}