Xiph.org Offers New CELT Demonstrations

Just before the holidays the folks at Xiph.org put up a nice demonstration page with a lot of detail about their CELT codec. Word of this new offering was announced on the IETF CODEC mailing list.

The samples and explanations provided are first rate. They clearly illustrate the merit in ultra-low-latency for some applications, as well as exemplify how CELT currently fares against other common codecs at a variety of bit-rates and with various types of source material.

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IETF’s New Codec To Be Known As Opus

As someone who’s passionately involved spreading the gospel of HDVoice I’ve been following the mailing list of the IETF CODEC Working Group. They’ve been working towards a new IETF RFC on a brand new wideband codec standard.

Starting with four submissions from Broadvoice, SpiritDSP, Skype and Xiph.org I think that they have made startlingly good progress over the past year. The group has actually arrived at a solution that provides for a codec that is a hybrid of SILK and CELT. It was recently announced on the mailing list that this new hybrid codec is to be known as “Opus.”

At IETF78 in Nagasaki, Japan the working group met to further their efforts. There’s a good recording of the session that, amongst other things, gives considerable detail about the hybrid nature of Opus.

There has been close co-operation between developers at Skype and Jean-Marc Valin of Xiph.org, such that they already have sample code running and have conducted some structured listening tests. The results of the listening tests are reported to be excellent.

It’s very interesting how the hybrid codec works. It can leverage both CELT and SILK principles acting on different frequency bands to generate the most optimal audio for a given bit-rate. It supports a wide range of sample rates from 8 KHz (PSTN narrowband) to 48 KHz (production quality audio) and bit-rates from 8 kbps to 128+ kbps per audio channel.

Opus may have a huge role to play in our transition away from the legacy PSTN. It’s very encouraging to hear that the CODEC Working Group is progressing so quickly.

HDVoice In Service Of Online Radio: Part 3

Sometimes the simplest questions result in the most interesting path of investigation. So it has been with Soljon’s initial question;

I am looking for an IP phone that supports G.722 and has audio inputs / outputs so I can connect it to my mixer. We are trying to connect two studios together for an online radio station. I have yet to find anything other than high end Polycom gear that has something like RCA in/out jacks. Have you by any chance come across anything?

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