Opus is a totally open, royalty-free, highly versatile audio codec. Opus is unmatched for interactive
speech and music transmission over the Internet, but is also intended for storage and streaming
applications. It is standardized by the Internet Engineering Task Force (IETF) as RFC 6716
which incorporated technology from Skype’s SILK codec and Xiph.Org’s CELT codec.
Opus can handle a wide range of audio applications, including Voice over IP, videoconferencing,
in-game chat, and even remote live music performances. It can scale from low bitrate narrowband
speech to very high quality stereo music. Supported features are:
Bitrates from 6 kb/s to 510 kb/s
Sampling rates from 8 kHz (narrowband) to 48 kHz (fullband)
Frame sizes from 2.5 ms to 60 ms
Support for both constant bitrate (CBR) and variable bitrate (VBR)
Audio bandwidth from narrowband to fullband
Support for speech and music
Support for mono and stereo
Support for up to 255 channels (multistream frames)
Dynamically adjustable bitrate, audio bandwidth, and frame size
Good loss robustness and packet loss concealment (PLC)
Floating point and fixed-point implementation
You can read the full specification, including the reference implementation, in RFC 6716.
An up-to-date implementation of the Opus standard is also available from the downloads page.
This Opus 1.2.1 minor release fixes a relatively rare
issue where the 1.2 encoder would wrongly assume a signal to be bandlimited to 12 kHz and not encode frequencies
between 12 and 20 kHz. This only happens on a few clips, but it is good to update to avoid a potential
loss of quality.
There are no other changes compared to 1.2. Please report any problems.
Opus 1.2-rc1 is
the first release candidate of the upcoming Opus 1.2 release. If no
issues are found with it, it will soon become 1.2-final, so we encourage
everyone to give it a try. Changes compared to 1.2-beta include:
Improves quality on files with powerful tones that cause MDCT leakage
Improves bit allocation on mode transitions (CELT to/from SILK/hybrid)
More ARM Neon optimizations
Fixes to the speech/music detection at the very beginning of files
Fixes to the unit tests (fixes illegal instructions and –disable-static)