CD-quality voice heads for Skype via newly standardised Opus codec

The royalty-free audio codec, which is also backed by Mozilla and is the first of its kind to gain official ratification from the IETF, should see widespread adoption as it is integral to the nascent WebRTC real-time communications standard.

Opus, a low-latency audio codec for handling voice and streaming sound, has become the first royalty-free codec of its kind to be officially standardised.

The codec, standardised by the Internet Engineering Task Force (IETF) this week, is the brainchild of Mozilla and the Microsoft-owned Skype, with involvement from Google, Broadcom, and Octasic as well. It will be used for applications such as VoIP — including Skype itself — and live music performances.

Opus is also, alongside G.711, one of the two audio codecs that will be mandatory for those implementing the WebRTC real-time communications standard.

Microsoft, Broadcom and all contributed patents to the standard on an "open-source-compatible" basis. According to the Opus licensing terms the codec can be used by anyone as long as they "are not trying to attack" Opus with their own patents.

Opus essentially melds Skype's own SILK voice codec, which the company has used since 2009 for its Skype-to-Skype calls, with's CELT music codec.

"If you'll pardon the pun, Opus will make a quiet but crystal clear entry into the world — most people will take for granted the high sound fidelity when it arrives in the Skype client, through browsers and gateways, and we hope on mobile phones, game consoles and conference rooms, too," Skype engineering chief Karlheinz Wurm wrote in a blog post on Wednesday.

Wurm noted that Opus would provide CD-quality voice and music, adding that it was "the first codec with state-of-the-art performance for any type of audio signal and any application (communications, streaming and storage) under any condition".

In a post on Tuesday, Mozilla also noted that Opus would 'beat' existing competitors such as Vorbis and HE-ACC.

It is still early days for Opus, of course, but the codec is already supported in Firefox, GStreamer, FFMpeg, foobar2000, K-Lite Codec Pack, and lavfilters. It will soon be supported in VLC, rockbox and Mumble, too.

Google's backing of WebRTC should also see Opus supported in Chrome, but Microsoft has its own rival to WebRTC in the works, named CU-RTC-Web.

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