Opus (audio format)

OpusOpus audio format.opusaudio standardIETF Opuslibopusofficial file formatOpus (audio codec)Opus (codec)Opus audio
Opus is a lossy audio coding format developed by the Xiph.Org Foundation and standardized by the Internet Engineering Task Force, designed to efficiently code speech and general audio in a single format, while remaining low-latency enough for real-time interactive communication and low-complexity enough for low-end embedded processors.wikipedia
253 Related Articles

Audio coding format

audio codingaudio coding standardaudio compression format
Opus is a lossy audio coding format developed by the Xiph.Org Foundation and standardized by the Internet Engineering Task Force, designed to efficiently code speech and general audio in a single format, while remaining low-latency enough for real-time interactive communication and low-complexity enough for low-end embedded processors.
Examples of audio coding formats include MP3, AAC, Vorbis, FLAC, and Opus.

CELT

Constrained Energy Lapped Transform
Opus combines the speech-oriented LPC-based SILK algorithm and the lower-latency MDCT-based CELT algorithm, switching between or combining them as needed for maximal efficiency.
Development of the format was maintained by the Xiph.Org Foundation (as part of the Ogg codec family) and later coordinated by the Opus working group of the Internet Engineering Task Force (IETF).

Speex

SPX.spxlibspeex
Opus replaces both Vorbis and Speex for new applications, and several blind listening tests have ranked it higher-quality than any other standard audio format at any given bitrate until transparency is reached, including MP3, AAC, and HE-AAC.
Xiph.Org now considers Speex obsolete; its successor is the more modern Opus codec, which surpasses its performance in all areas.

SILK

Skype SILK
Opus combines the speech-oriented LPC-based SILK algorithm and the lower-latency MDCT-based CELT algorithm, switching between or combining them as needed for maximal efficiency.
It has been extended to the Internet standard Opus codec.

Vorbis

Ogg VorbisOGGaoTuV
Opus replaces both Vorbis and Speex for new applications, and several blind listening tests have ranked it higher-quality than any other standard audio format at any given bitrate until transparency is reached, including MP3, AAC, and HE-AAC.

Variable bitrate

VBRvariable bit ratevariable
Opus supports constant and variable bitrate encoding from 6 kbit/s to 510 kbit/s, frame sizes from 2.5 ms to 60 ms, and five sampling rates from 8 kHz (with 4 kHz bandwidth) to 48 kHz (with 20 kHz bandwidth, the human hearing range).
MP3, WMA and AAC audio files can optionally be encoded in VBR, while Opus, Vorbis are always in VBR.

Xiph.Org Foundation

Xiph.orgXiphXiph QuickTime Components
Opus is a lossy audio coding format developed by the Xiph.Org Foundation and standardized by the Internet Engineering Task Force, designed to efficiently code speech and general audio in a single format, while remaining low-latency enough for real-time interactive communication and low-complexity enough for low-end embedded processors.

Ogg

OGM.oggOgg Writ
Opus was originally specified for encapsulation in Ogg containers, specified as, and for Ogg Opus files the filename extension is recommended.
The audio layer is most commonly provided by the music-oriented Vorbis format or its successor Opus.

WebM

.webm155-165 kbps Opus WebM
Opus streams are also supported in Matroska, WebM, MPEG-TS, and MP4. Although Internet Explorer will not provide Opus playback natively, support for the format is built into the Edge browser, along with VP9, for full WebM support.
In 2013, it was updated to accommodate VP9 video and Opus audio.

Modified discrete cosine transform

MDCTModulated Lapped Transformtime-domain aliasing cancellation
Opus combines the speech-oriented LPC-based SILK algorithm and the lower-latency MDCT-based CELT algorithm, switching between or combining them as needed for maximal efficiency.
It is employed in most modern audio coding standards, including MP3, Dolby Digital (AC-3), Vorbis (Ogg), Windows Media Audio (WMA), ATRAC, Cook, Advanced Audio Coding (AAC), LDAC, Dolby AC-4, MPEG-H 3D Audio, as well as speech coding standards such as AAC-LD (LD-MDCT), G.722.1, G.729.1, CELT, and Opus.

Voice over IP

VoIPVoice over Internet Protocolvoice-over-IP
Opus is widely used as the voice-over-IP (VoIP) codec in applications such as WhatsApp and the PlayStation 4.
Popular codecs include the MDCT-based AAC-LD (used in FaceTime), the LPC/MDCT-based Opus (used in WhatsApp), the LPC-based SILK (used in Skype), μ-law and A-law versions of G.711, G.722, and an open source voice codec known as iLBC, a codec that uses only 8 kbit/s each way called G.729.

WhatsApp

WhatsApp MessengerWhatsApp Inc.social media
Opus is widely used as the voice-over-IP (VoIP) codec in applications such as WhatsApp and the PlayStation 4.
WhatsApp's voice codec is Opus, which uses the modified discrete cosine transform (MDCT) and linear predictive coding (LPC) audio compression algorithms.

MP3

.mp3MP3 downloadMP3 files
Opus replaces both Vorbis and Speex for new applications, and several blind listening tests have ranked it higher-quality than any other standard audio format at any given bitrate until transparency is reached, including MP3, AAC, and HE-AAC.
There are also open compression formats like Opus and Vorbis that are available free of charge and without any known patent restrictions.

Networked music performance

network musicnetwork performance practicesSoundWire, CCRMA
Opus has the low algorithmic delay (26.5 ms by default) necessary for use as part of a real-time communication link, permitting natural conversation, networked music performances, and live lip sync; by trading-off quality or bitrate, the delay can be reduced down to 5 ms. Its delay is exceptionally low compared to competing codecs, which require well over 100 ms, yet Opus performs very competitively with these formats in terms of quality per bitrate.

High-Efficiency Advanced Audio Coding

AAC+HE-AACeAAC+
Opus replaces both Vorbis and Speex for new applications, and several blind listening tests have ranked it higher-quality than any other standard audio format at any given bitrate until transparency is reached, including MP3, AAC, and HE-AAC.
A 2011 Public Listening Test compared the two best-rated HE AAC encoders at that time to Opus and Ogg Vorbis, indicated statistically significant superiority at 64 kbit/s for Opus over all other contenders, and second ranked Apple HE AAC statistically superior to both Ogg Vorbis and Nero HE AAC which were tied for third place.

Advanced Audio Coding

AACAAC-LCMPEG-4 AAC
Opus replaces both Vorbis and Speex for new applications, and several blind listening tests have ranked it higher-quality than any other standard audio format at any given bitrate until transparency is reached, including MP3, AAC, and HE-AAC.

Digital container format

container formatcontainercontainer formats
Opus packets are not self-delimiting, but are designed to be used inside a container of some sort which supplies the decoder with each packet's length.

Internet Speech Audio Codec

iSAC
The SILK part has been under development at Skype since January 2007 as the successor of their SVOPC, an internal project to make the company independent from third-party codecs like iSAC and iLBC and respective license payments.

AIMP

Such support was added to AIMP, Amarok, cmus, Music Player Daemon, foobar2000, Mpxplay, MusicBee, SMplayer, VLC media player, Winamp and Xmplay audio players; Icecast, Airtime (software) audio streaming software; and Asunder audio CD ripper, CDBurnerXP CD burner, FFmpeg, Libav and MediaCoder media encoding tools.
AIMP can play many file types, including MP3, Advanced Audio Coding (AAC), Dolby AC-3, Ogg Vorbis, Opus, Speex, Windows Media Audio, Apple Lossless, FLAC, WAV and Audio CDs.

VP9

VP10VP9 hardware implementations
Although Internet Explorer will not provide Opus playback natively, support for the format is built into the Edge browser, along with VP9, for full WebM support.
The combination of VP9 video and Opus audio in the WebM container, as served by YouTube, is supported by roughly 4⁄5 of the browser market (mobile included) as of June 2018.

Amarok (software)

AmarokAmarok Media Player
Such support was added to AIMP, Amarok, cmus, Music Player Daemon, foobar2000, Mpxplay, MusicBee, SMplayer, VLC media player, Winamp and Xmplay audio players; Icecast, Airtime (software) audio streaming software; and Asunder audio CD ripper, CDBurnerXP CD burner, FFmpeg, Libav and MediaCoder media encoding tools.

Music Player Daemon

MPDCantataMPC
Such support was added to AIMP, Amarok, cmus, Music Player Daemon, foobar2000, Mpxplay, MusicBee, SMplayer, VLC media player, Winamp and Xmplay audio players; Icecast, Airtime (software) audio streaming software; and Asunder audio CD ripper, CDBurnerXP CD burner, FFmpeg, Libav and MediaCoder media encoding tools.

MusicBee

Such support was added to AIMP, Amarok, cmus, Music Player Daemon, foobar2000, Mpxplay, MusicBee, SMplayer, VLC media player, Winamp and Xmplay audio players; Icecast, Airtime (software) audio streaming software; and Asunder audio CD ripper, CDBurnerXP CD burner, FFmpeg, Libav and MediaCoder media encoding tools.

FFmpeg

SnowLAV Filterslibavformat
The FFmpeg project has encoder and decoder implementations not derived from the reference library.

Surround sound

Surround5.1 surround sound5.1
On July 11, 2013, libopus 1.0.3 brought bug fixes and a new Surround sound API that improves channel allocation and quality, especially for LFE.