Opus is an Open Source codec standardized by the [http://www.ietf.org/ IETF].

See RFC 6716.

• Project page: http://opus-codec.org/
• Opus-FAQ: https://wiki.xiph.org/OpusFAQ
• http://people.xiph.org/~xiphmont/demo/opus/demo3.shtml
• Opus on Wikipedia: http://de.wikipedia.org/wiki/Opus_%28Audioformat%29
• Examples and details http://octasic.com/en/tech/opus_audio_codec.php
• Posting about the standardization of Opus: http://xiph.org/press/2012/rfc-6716/

Opus has different modes (Celt mode, Silk mode and a Hybrid mode): The first one has the best performance.

Newer versions of Opus are always backward compatible, so there will be no codec problems for example in Mumble as with Celt, Speex, Opus.

See Codecs in Mumble

• http://www.opus-codec.org/examples/

Mumble uses the Opus codec since version 1.2.4.

We made few tests in Mumble, few subjective facts:

• Even with an audio bandwidth of only 8 kbit/s Opus spoken word is easy to understand. With CELT it sounds very distorted.
• Opus with 30 kbit/s sounds similar to CELT with 50 kbit/s.

Another advantage (found on freenode in #mumble):

• Correction in case packetloss sounds better with Opus.