Opus Audio: Pairing Skype's SILC With CELT

For those that haven't heard, the IETF Codec Working Group has paired the technology from Skype's SILC codec with the CELT codec from Xiph.Org to form the Opus Interactive Audio Codec. This new codec can be used for VoIP, live music streaming, and more.

Information on the Opus Codec is available from Opus-Codec.org. On the site it lists the features as:

- Sampling rates from 8 to 48 kHz
- Bit-rates from 6 kb/s 510 kb/s
- Support for both constant bit-rate (CBR) and variable bit-rate (VBR)
- Audio bandwidth from narrowband to full-band
- Support for speech and music
- Support for mono and stereo
- Frame sizes from 2.5 ms to 60 ms
- Dynamically adjustable bitrate, audio bandwidth, and frame size
- Good loss robustness and packet loss concealment (PLC)
- Floating point and fixed-point implementation

This codec from the Internet Engineering Task Force (IETF) will be royalty-free. Aside from Skype being a known name involved with the project led by the IETF, Mozilla has also been involved in the Opus Audio Codec. This codec wasn't just announced, but is still being developed and not widely reported on. Thanks to a Phoronix reader ("markg85") for bringing it up as it carries a lot of potential for the open-source VoIP world (and other applications too) as a low-delay wide-band codec.

The latest release of Opus is version 0.9.14 and was published on the 17th of May.