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Skype and a New Audio Codec

Skype has quietly revolutionized the sound quality of our daily communications. We introduced SILK, our own audio codec, to make our calls sound more like being there in person in January 2009. Since then, we’ve used it to serve more than 750 billion Skype-to-Skype minutes.

Skype initiated the idea of developing and standardizing a codec ‘built for the internet’ and usable by everybody else within the IETF back in March 2009. Senior Skype Architect and Distinguished Engineer Koen Vos and our audio team began work on it in June 2009. After objections were overcome, Opus was submitted to the IETF in September 2010.

We believe that Opus will be the new, free, go-to codec for real time communication, streaming and storage, and we are excited to see its birth as a fully-fledged IETF standard.

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.

In the past, you needed a myriad of different codecs to handle all audio tasks, all with different licensing or pricing agreements. Now you just need one: Opus.

We think it’s worth making some noise for Opus, celebrating that it is built on Skype’s highly-successful SILK codec and thanking both the Skype and our friends in the IETF community who have worked with us – the people who made it happen.

We hope to see wide adoption of Opus, and we care passionately about audio and video quality. We really believe that bringing consistent audio quality to all our users on every device will make everyone’s communications a little more wonderful every day.

This is the kind of goal that drives our engineers at Skype. We hope that the fact that Opus is now a standard will mean that it will be more widely adopted, helping us in our mission to deliver better quality as part of improving communications for the Skype community no matter the platform or device.

  • Opus will improve audio experiences across the spectrum from narrowband mono to fullband stereo for both voice and music.
  • Opus is higher-quality than a broad collection of existing codecs for both voice and music. If you don’t believe us, take a look at the test results.
  • We believe that mobile data network operators will love it because it is more efficient, using up fewer megabytes.
  • The innovation in Opus fuses SILK for voice with Xiph.Org’s CELT codec for music.
  • There’s even a hybrid mode using both codecs at the same time.
  • Opus is versatile, efficient and smart, working across an unprecedented range of bitrates, sampling rates and frame sizes. It is efficient for speech yet still great for music.

We believe that Opus is 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.

Because Opus was designed for the Internet, it can adjust seamlessly on-the-fly between any of its operating modes to adjust to variations in available internet resources, whether moving from 3G to WiFi or competing with the house next door for broadband bandwidth.

Furthermore, it has multiple mechanisms to deal with and recover from packet loss plaguing the network, making for fewer annoying gaps in conversation and lost moments in your precious calls.

Future Skype users will talk in CD quality (fullband stereo) using Skype.

Naturally, we’re quite proud to have had a part to play in bringing Opus to the world, excited to where it will take us and what it means for the Skype community.

Koen Vos, who I introduced above, will share more background about Opus and his team which played a key role in its development in an upcoming blog post. Stay tuned.

For a full presentation and audio demo of Opus, please view the video below:



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