Comment 1 for bug 1411576

Also does not recognise .opus files, "Opus data can be encapsulated in Ogg containers. The content of such Ogg Opus streams should be specified as audio/ogg; codecs=opus and for Ogg Opus files the .opus filename extension is recommended."

http://tools.ietf.org/pdf/draft-ietf-codec-oggopus-06.pdf