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Opus is a
lossy In information technology, lossy compression or irreversible compression is the class of data compression methods that uses inexact approximations and partial data discarding to represent the content. These techniques are used to reduce data size ...
audio coding format An audio coding format (or sometimes audio compression format) is a content representation format for storage or transmission of digital audio (such as in digital television, digital radio and in audio and video files). Examples of audio coding ...
developed by the
Xiph.Org Foundation Xiph.Org Foundation is a nonprofit organization that produces free multimedia formats and software tools. It focuses on the Ogg family of formats, the most successful of which has been Vorbis, an open and freely licensed audio format and codec de ...
and standardized by the
Internet Engineering Task Force The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and a ...
, designed to efficiently code speech and general audio in a single format, while remaining
low-latency Latency, from a general point of view, is a time delay between the cause and the effect of some physical change in the system being observed. Lag, as it is known in gaming circles, refers to the latency between the input to a simulation and ...
enough for real-time interactive communication and low-complexity enough for low-end embedded processors. Opus replaces both
Vorbis Vorbis is a free and open-source software project headed by the Xiph.Org Foundation. The project produces an audio coding format and software reference encoder/decoder (codec) for lossy audio compression. Vorbis is most commonly used in conju ...
and
Speex Speex is an audio compression codec specifically tuned for the reproduction of human speech and also a free software speech codec that may be used on VoIP applications and podcasts. It is based on the CELP speech coding algorithm.Xiph.OrIntrodu ...
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 MP3 (formally MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) is a coding format for digital audio developed largely by the Fraunhofer Society in Germany, with support from other digital scientists in the United States and elsewhere. Origin ...
,
AAC AAC may refer to: Aviation * Advanced Aircraft, a company from Carlsbad, California * Alaskan Air Command, a radar network * American Aeronautical Corporation, a company from Port Washington, New York * American Aviation, a company from Clevela ...
, and
HE-AAC High-Efficiency Advanced Audio Coding (HE-AAC) is an audio coding format for lossy data compression of digital audio defined as an MPEG-4 Audio profile in ISO/ IEC 14496–3. It is an extension of Low Complexity AAC (AAC-LC) optimized for l ...
. Opus combines the speech-oriented LPC-based
SILK Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the co ...
algorithm and the lower-latency
MDCT The modified discrete cosine transform (MDCT) is a transform based on the type-IV discrete cosine transform (DCT-IV), with the additional property of being lapped: it is designed to be performed on consecutive blocks of a larger dataset, where s ...
-based
CELT The Celts (, see pronunciation for different usages) or Celtic peoples () are. "CELTS location: Greater Europe time period: Second millennium B.C.E. to present ancestry: Celtic a collection of Indo-European peoples. "The Celts, an ancient ...
algorithm, switching between or combining them as needed for maximal efficiency. Bitrate, audio bandwidth, complexity, and algorithm can all be adjusted seamlessly in each frame. Opus has the low algorithmic delay (26.5 ms by default) necessary for use as part of a real-time communication link,
networked music performance A networked music performance or network musical performance is a real-time interaction over a computer network that enables musicians in different locations to perform as if they were in the same room. These interactions can include performances, ...
s, and live
lip sync Lip sync or lip synch (pronounced , the same as the word ''sink'', short for lip synchronization) is a technical term for matching a speaking or singing person's lip movements with sung or spoken vocals. Audio for lip syncing is generated thr ...
; 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. As an
open format An open file format is a file format for storing digital data, defined by an openly published specification usually maintained by a standards organization, and which can be used and implemented by anyone. Open file format is licensed with open lic ...
standardized through RFC 6716, a
reference implementation In the software development process, a reference implementation (or, less frequently, sample implementation or model implementation) is a program that implements all requirements from a corresponding specification. The reference implementation o ...
called libopus is available under the
New BSD License BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements. The original BSD lice ...
. The reference has both
fixed-point Fixed point may refer to: * Fixed point (mathematics), a value that does not change under a given transformation * Fixed-point arithmetic, a manner of doing arithmetic on computers * Fixed point, a benchmark (surveying) The term benchmark, be ...
and
floating-point In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can be r ...
optimizations for low- and high-end devices, with
SIMD Single instruction, multiple data (SIMD) is a type of parallel processing in Flynn's taxonomy. SIMD can be internal (part of the hardware design) and it can be directly accessible through an instruction set architecture (ISA), but it should ...
optimizations on platforms that support them. All known
software patent A software patent is a patent on a piece of software, such as a computer program, libraries, user interface, or algorithm. Background A patent is a set of exclusionary rights granted by a state to a patent holder for a limited period of time, ...
s that cover Opus are licensed under
royalty-free Royalty-free (RF) material subject to copyright or other intellectual property rights may be used without the need to pay royalties or license fees for each use, per each copy or volume sold or some time period of use or sales. Computer standard ...
terms. Opus is widely used as the
voice over IP Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet ...
(VoIP) codec in applications such as
Discord Discord is a VoIP and instant messaging social platform. Users have the ability to communicate with voice calls, video calls, text messaging, media and files in private chats or as part of communities called "servers".The developer documenta ...
,
WhatsApp WhatsApp (also called WhatsApp Messenger) is an internationally available freeware, cross-platform, centralized instant messaging (IM) and voice-over-IP (VoIP) service owned by American company Meta Platforms (formerly Facebook). It allows u ...
, and the
PlayStation 4 The PlayStation 4 (PS4) is a home video game console developed by Sony Interactive Entertainment. Announced as the successor to the PlayStation 3 in February 2013, it was launched on November 15, 2013, in North America, November 29, 2013 in ...
.


Features

Opus supports constant and
variable bitrate Variable bitrate (VBR) is a term used in telecommunications and computing that relates to the bitrate used in sound or video encoding. As opposed to constant bitrate (CBR), VBR files vary the amount of output data per time segment. VBR allows a ...
encoding from 6  kbit/s to 510 kbit/s (or up to 256 kbit/s per channel for multi-channel tracks), frame sizes from 2.5 ms to 60 ms, and five
sampling rate In signal processing, sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave to a sequence of "samples". A sample is a value of the signal at a point in time and/or spa ...
s from 8 kHz (with 4 kHz bandwidth) to 48 kHz (with 20 kHz bandwidth, the human
hearing range Hearing range describes the range of frequencies that can be heard by humans or other animals, though it can also refer to the range of levels. The human range is commonly given as 20 to 20,000 Hz, although there is considerable variatio ...
). An Opus stream can support up to 255 audio channels, and it allows channel coupling between channels in groups of two using mid-side coding. Opus has very short latency (26.5 ms using the default 20 ms frames and default application setting), which makes it suitable for real-time applications such as
telephony Telephony ( ) is the field of technology involving the development, application, and deployment of telecommunication services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is i ...
,
Voice over IP Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet ...
and
videoconferencing Videotelephony, also known as videoconferencing and video teleconferencing, is the two-way or multipoint reception and transmission of audio signal, audio and video signals by people in different locations for Real-time, real time communication. ...
; research by
Xiph Xiph.Org Foundation is a nonprofit organization that produces free multimedia formats and software tools. It focuses on the Ogg family of formats, the most successful of which has been Vorbis, an open and freely licensed audio format and codec de ...
led to the
CELT The Celts (, see pronunciation for different usages) or Celtic peoples () are. "CELTS location: Greater Europe time period: Second millennium B.C.E. to present ancestry: Celtic a collection of Indo-European peoples. "The Celts, an ancient ...
codec, which allows the highest quality while maintaining low delay. In any Opus stream, the bitrate, bandwidth, and delay can be continually varied without introducing any distortion or discontinuity; even mixing packets from different streams will cause a smooth change, rather than the distortion common in other codecs. Unlike Vorbis, Opus does not require large codebooks for each individual file, making it more efficient for short clips of audio and more resilient. The Opus format is based on a combination of the full-bandwidth
CELT The Celts (, see pronunciation for different usages) or Celtic peoples () are. "CELTS location: Greater Europe time period: Second millennium B.C.E. to present ancestry: Celtic a collection of Indo-European peoples. "The Celts, an ancient ...
format and the speech-oriented
SILK Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the co ...
format, both heavily modified: CELT is based on the
modified discrete cosine transform The modified discrete cosine transform (MDCT) is a transform based on the type-IV discrete cosine transform (DCT-IV), with the additional property of being lapped: it is designed to be performed on consecutive blocks of a larger dataset, where su ...
(MDCT) that most music codecs use, using
CELP Code-excited linear prediction (CELP) is a linear predictive speech coding algorithm originally proposed by Manfred R. Schroeder and Bishnu S. Atal in 1985. At the time, it provided significantly better quality than existing low bit-rate algori ...
techniques in the frequency domain for better prediction, while SILK uses
linear predictive coding Linear predictive coding (LPC) is a method used mostly in audio signal processing and speech processing for representing the spectral envelope of a digital signal of speech in compressed form, using the information of a linear predictive model. ...
(LPC) and an optional Long-Term Prediction filter to model speech. In Opus, both were modified to support more frame sizes, as well as further algorithmic improvements and integration, such as using CELT's range encoder for both types. To minimize overhead at low bitrates, if latency is not as pressing, SILK has support for packing multiple 20 ms frames together, sharing context and headers; SILK also allows Low Bit-Rate Redundancy (LBRR) frames, allowing low-quality packet loss recovery. CELT includes both spectral replication and noise generation, similar to AAC's SBR and PNS, and can further save bits by filtering out all harmonics of tonal sounds entirely, then replicating them in the decoder. Better tone detection is an ongoing project to improve quality. The format has three different modes: speech, hybrid, and CELT. When compressing speech, SILK is used for audio frequencies up to 8 kHz. If wider bandwidth is desired, a hybrid mode uses CELT to encode the frequency range above 8 kHz. The third mode is pure-CELT, designed for general audio. SILK is inherently VBR and cannot hit a bitrate target, while CELT can always be encoded to any specific number of bytes, enabling hybrid and CELT mode when CBR is required. SILK supports frame sizes of 10, 20, 40 and 60 ms. CELT supports frame sizes of 2.5, 5, 10 and 20 ms. Thus, hybrid mode only supports frame sizes of 10 and 20 ms; frames shorter than 10 ms will always use CELT mode. A typical Opus packet contains a single frame, but packets of up to 120 ms are produced by combining multiple frames per packet. Opus can transparently switch between modes, frame sizes, bandwidths, and channel counts on a per-packet basis, although specific applications may choose to limit this. The reference implementation is written in C and compiles on hardware architectures with or without a
floating-point unit In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can be ...
, although floating-point is currently required for audio bandwidth detection (dynamic switching between SILK, CELT, and hybrid encoding) and most speed optimizations.


Containers

Opus packets are not self-delimiting, but are designed to be used inside a
container A container is any receptacle or enclosure for holding a product used in storage, packaging, and transportation, including shipping. Things kept inside of a container are protected on several sides by being inside of its structure. The term ...
of some sort which supplies the decoder with each packet's length. Opus was originally specified for encapsulation in
Ogg Ogg is a free, open container format maintained by the Xiph.Org Foundation. The authors of the Ogg format state that it is unrestricted by software patents and is designed to provide for efficient streaming and manipulation of high-quality di ...
containers, specified as audio/ogg; codecs=opus, and for Ogg Opus files the .opus filename extension is recommended. Opus streams are also supported in
Matroska Matroska is a project to create a container format that can hold an unlimited number of video, audio, picture, or subtitle tracks in one file. The Matroska Multimedia Container is similar in concept to other containers like AVI, MP4, or Adva ...
,
WebM WebM is an audiovisual media file format. It is primarily intended to offer a royalty-free alternative to use in the HTML5 video and the HTML5 audio elements. It has a sister project, WebP, for images. The development of the format is sponsored ...
,
MPEG-TS MPEG transport stream (MPEG-TS, MTS) or simply transport stream (TS) is a standard digital container format for transmission and storage of audio, video, and Program and System Information Protocol (PSIP) data. It is used in broadcast systems ...
, and MP4. Alternatively, each Opus packet may be wrapped in a
network packet In telecommunications and computer networking, a network packet is a formatted unit of data carried by a packet-switched network. A packet consists of control information and user data; the latter is also known as the ''payload''. Control inform ...
which supplies the packet length. Opus packets may be sent over an ordered datagram protocol such as RTP. An optional self-delimited packet format is defined in an appendix to the specification. This uses one or two additional bytes per packet to encode the packet length, allowing packets to be concatenated without encapsulation.


Bandwidth and sampling rate

Opus allows the following bandwidths during encoding. Opus compression does not depend on the input sample rate; timestamps are measured in 48 kHz units even if the full bandwidth is not used. Likewise, the output sample rate may be freely chosen. For example, audio can be input at 16 kHz yet be set to encode only narrowband audio.


History

Opus was proposed for the standardization of a new audio format at the IETF, which was eventually accepted and granted by the ''codec''
working group A working group, or working party, is a group of experts working together to achieve specified goals. The groups are domain-specific and focus on discussion or activity around a specific subject area. The term can sometimes refer to an interdis ...
. It is based on two initially separate standard proposals from the Xiph.Org Foundation and Skype Technologies S.A. (now
Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washingt ...
). Its main developers are Jean-Marc Valin (Xiph.Org, Octasic,
Mozilla Corporation The Mozilla Corporation (stylized as moz://a) is a wholly owned subsidiary of the Mozilla Foundation that coordinates and integrates the development of Internet-related applications such as the Firefox web browser, by a global community of open- ...
), Koen Vos (Skype), and Timothy B. Terriberry (Xiph.Org, Mozilla Corporation). Among others, Juin-Hwey (Raymond) Chen (
Broadcom Broadcom Inc. is an American designer, developer, manufacturer and global supplier of a wide range of semiconductor and infrastructure software products. Broadcom's product offerings serve the data center, networking, software, broadband, wirel ...
), Gregory Maxwell (Xiph.Org,
Wikimedia The Wikimedia Foundation, Inc., or Wikimedia for short and abbreviated as WMF, is an American 501(c)(3) nonprofit organization headquartered in San Francisco, California and registered as a charitable foundation under local laws. Best kno ...
), and Christopher Montgomery (Xiph.Org) were also involved. The development of the CELT part of the format goes back to thoughts on a successor for
Vorbis Vorbis is a free and open-source software project headed by the Xiph.Org Foundation. The project produces an audio coding format and software reference encoder/decoder (codec) for lossy audio compression. Vorbis is most commonly used in conju ...
under the working name ''Ghost''. As a newer speech codec from the Xiph.Org Foundation, Opus replaces Xiph's older speech codec
Speex Speex is an audio compression codec specifically tuned for the reproduction of human speech and also a free software speech codec that may be used on VoIP applications and podcasts. It is based on the CELP speech coding algorithm.Xiph.OrIntrodu ...
, an earlier project of Jean-Marc Valin. CELT has been worked on since November 2007. 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 Internet Low Bitrate Codec (iLBC) is a royalty-free narrowband speech audio coding format and an open-source reference implementation (codec), developed by Global IP Solutions (GIPS) formerly Global IP Sound (acquired by Google Inc in 2011). ...
and respective license payments. In March 2009, Skype suggested the development and standardization of a wideband audio format within the IETF. Nearly a year passed with much debate on the formation of an appropriate
working group A working group, or working party, is a group of experts working together to achieve specified goals. The groups are domain-specific and focus on discussion or activity around a specific subject area. The term can sometimes refer to an interdis ...
. Representatives of several companies which were taking part in the standardization of patent-encumbered competing format, including
Polycom Poly, formerly Polycom, a part of HP Inc., is an American multinational corporation that develops video, voice and content collaboration and communication technology. Polycom was co-founded in 1990 by Brian L Hinman and Jeffrey Rodman. In 2018 ...
and
Ericsson (lit. "Telephone Stock Company of LM Ericsson"), commonly known as Ericsson, is a Swedish multinational networking and telecommunications company headquartered in Stockholm. The company sells infrastructure, software, and services in informa ...
—the creators and licensors of G.719—as well as
France Télécom Orange S.A. (), formerly France Télécom S.A. (stylized as france telecom) is a French multinational telecommunications corporation. It has 266 million customers worldwide and employs 89,000 people in France, and 59,000 elsewhere. In 2015, ...
,
Huawei Huawei Technologies Co., Ltd. ( ; ) is a Chinese multinational technology corporation headquartered in Shenzhen, Guangdong, China. It designs, develops, produces and sells telecommunications equipment, consumer electronics and various smart ...
and the
Orange Labs Orange S.A. (), formerly France Télécom S.A. (stylized as france telecom) is a French multinational corporation, multinational telecommunications corporation. It has 266 million customers worldwide and employs 89,000 people in France, and 5 ...
(department of France Télécom), which were involved in the creation of G.718, stated objections against the start of the standardization process for a royalty-free format. (Some of the opponents would later claim patent rights that Xiph dismissed; see below.) The working group finally formed in February 2010, and even the corresponding Study Group 16 from the ITU-T pledged to support its work. In July 2010, a prototype of a hybrid format was presented that combined the two proposed format candidates SILK and CELT. In September 2010, Opus was submitted to the IETF as proposal for standardization. For a short time the format went under the name of ''Harmony'' before it got its present name in October 2010. At the beginning of February 2011, the
bitstream A bitstream (or bit stream), also known as binary sequence, is a sequence of bits. A bytestream is a sequence of bytes. Typically, each byte is an 8-bit quantity, and so the term octet stream is sometimes used interchangeably. An octet may ...
format was tentatively frozen, subject to last changes. Near the end of July 2011, Jean-Marc Valin was hired by the
Mozilla Corporation The Mozilla Corporation (stylized as moz://a) is a wholly owned subsidiary of the Mozilla Foundation that coordinates and integrates the development of Internet-related applications such as the Firefox web browser, by a global community of open- ...
to continue working on Opus.


Finalization (1.0)

In November 2011, the working group issued the last call for changes on the bitstream format. The bitstream has been frozen since January 8, 2012. On July 2, 2012, Opus was approved by the
IETF The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and a ...
for standardization. The reference software entered release candidate state on August 8, 2012. The final specification was released as RFC 6716 on September 10, 2012. and versions 1.0 and 1.0.1 of the
reference implementation In the software development process, a reference implementation (or, less frequently, sample implementation or model implementation) is a program that implements all requirements from a corresponding specification. The reference implementation o ...
libopus were released the day after. On July 11, 2013, libopus 1.0.3 brought bug fixes and a new
Surround sound Surround sound is a technique for enriching the fidelity and depth of sound reproduction by using multiple audio channels from speakers that surround the listener ( surround channels). Its first application was in movie theaters. Prior to s ...
API that improves channel allocation and quality, especially for LFE.


1.1

On December 5, 2013, libopus 1.1 was released, incorporating overall speed improvements and significant encoder quality improvements: Tonality estimation boosts bitrate and quality for previousl
problematic samples
like harpsichords; automated speech/music detection improves quality in mixed audio; mid-side stereo reduces the bitrate needs of many songs; band precision boosting for improved transients; and DC rejection below 3 Hz. Two new VBR modes were added: unconstrained for more consistent quality, and temporal VBR that boosts louder frames and generally improves quality. libopus 1.1.1 was released on November 26, 2015, and 1.1.2 on January 12, 2016, both adding speed optimizations and bug fixes. July 15, 2016 saw the release of version 1.1.3 and includes bug fixes, optimizations, documentation updates and experimental
Ambisonics Ambisonics is a ''full-sphere'' surround sound format: in addition to the horizontal plane, it covers sound sources above and below the listener. Unlike some other multichannel surround formats, its transmission channels do not carry speaker si ...
work.


1.2

libopus 1.2 Beta was released on May 24, 2017. libopus 1.2 was released on June 20, 2017. Improvements brought in 1.2 allow it to create fullband music at bit rates as low as 32 kbit/s, and wideband speech at just 12 kbit/s. libopus 1.2 includes optional support for the decoder specification changes made in drafts of RFC 8251, improving the quality of output from such low-rate streams.


1.3

libopus 1.3 was released on October 18, 2018. The Opus 1.3 major release again brings quality improvements, new features, and bug fixes. Changes since 1.2.x include: * Improvements to voice activity detection (VAD) and speech/music classification using a recurrent neural network (RNN) * Support for ambisonics coding using channel mapping families 2 and 3 * Improvements to stereo speech coding at low bitrate * Using wideband speech encoding down to 9 kbit/s (mediumband is no longer used) * Making it possible to use SILK down to bitrates around 5 kbit/s * Minor quality improvement on tones * Enabling the spec fixes in RFC 8251 by default * Security/hardening improvements Notable bug fixes include: * Fixes to the CELT PLC * Bandwidth detection fixes


1.3.1

libopus 1.3.1 was released on April 12, 2019. This Opus 1.3.1 minor release fixes an issue with the analysis on files with digital silence (all zeros), especially on
x87 x87 is a floating-point-related subset of the x86 architecture instruction set. It originated as an extension of the 8086 instruction set in the form of optional floating-point coprocessors that worked in tandem with corresponding x86 CPUs. Thes ...
builds (mostly affects 32-bit builds). It also includes two new features: * A new OPUS_GET_IN_DTX query to know if the encoder is in DTX mode (last frame was either a comfort noise frame or not encoded at all) * A new (and still experimental) CMake-based build system that is eventually meant to replace the VS2015 build system (the
autotools The GNU Autotools, also known as the GNU Build System, is a suite of programming tools designed to assist in making source code packages portable to many Unix-like systems. It can be difficult to make a software program portable: the C compile ...
build system will stay)


Quality comparison and low-latency performance

Opus performs well at both low and high
bit rate In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time. The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction ...
s. In listening tests around 64 kbit/s, Opus shows superior quality compared to
HE-AAC High-Efficiency Advanced Audio Coding (HE-AAC) is an audio coding format for lossy data compression of digital audio defined as an MPEG-4 Audio profile in ISO/ IEC 14496–3. It is an extension of Low Complexity AAC (AAC-LC) optimized for l ...
codecs, which were previously dominant due to their use of the patented
spectral band replication Spectral band replication (SBR) is a technology to enhance audio or speech codecs, especially at low bit rates and is based on harmonic redundancy in the frequency domain. It can be combined with any audio compression codec: the codec itself tran ...
(SBR) technology.Next-Gen Low-Latency Open Codec Beats HE-AAC
Slashdot-Meldung vom 14. April 2011.
In listening tests around 96 kbit/s, Opus shows slightly superior quality compared to
AAC AAC may refer to: Aviation * Advanced Aircraft, a company from Carlsbad, California * Alaskan Air Command, a radar network * American Aeronautical Corporation, a company from Port Washington, New York * American Aviation, a company from Clevela ...
and significantly better quality compared to
Vorbis Vorbis is a free and open-source software project headed by the Xiph.Org Foundation. The project produces an audio coding format and software reference encoder/decoder (codec) for lossy audio compression. Vorbis is most commonly used in conju ...
and
MP3 MP3 (formally MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) is a coding format for digital audio developed largely by the Fraunhofer Society in Germany, with support from other digital scientists in the United States and elsewhere. Origin ...
. Opus has very low algorithmic delay, a necessity for use as part of a low- audio-latency communication link, which can permit natural conversation,
networked music performance A networked music performance or network musical performance is a real-time interaction over a computer network that enables musicians in different locations to perform as if they were in the same room. These interactions can include performances, ...
s, or
lip sync Lip sync or lip synch (pronounced , the same as the word ''sink'', short for lip synchronization) is a technical term for matching a speaking or singing person's lip movements with sung or spoken vocals. Audio for lip syncing is generated thr ...
at live events. Total algorithmic delay for an audio format is the sum of delays that must be incurred in the encoder and the decoder of a live audio stream regardless of processing speed and transmission speed, such as buffering audio samples into blocks or frames, allowing for window overlap and possibly allowing for noise-shaping look-ahead in a decoder and any other forms of look-ahead, or for an MP3 encoder, the use of bit reservoir. Total one-way latency below 150 ms is the preferred target of most
VoIP Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet ...
systems, to enable natural conversation with turn-taking little affected by delay. Musicians typically feel in-time with up to around 30 ms audio latency, roughly in accord with the fusion time of the
Haas effect Haas may refer to: People * Haas (surname) * Haas Visser 't Hooft (1905–1977), Dutch field hockey player Auto racing * Haas F1 Team, a 21st-century Formula 1 auto racing team * Haas Lola, a 20th-century Formula 1 auto racing team * Newman/Haa ...
, though matching playback delay of each user's own instrument to the round-trip latency can also help. It is suggested for lip sync that around 45–100 ms audio latency may be acceptable. Opus permits trading-off reduced quality or increased bitrate to achieve an even smaller algorithmic delay (5.0 ms minimum). While the reference implementation's default Opus frame is 20.0 ms long, the SILK layer requires a further 5.0 ms lookahead plus 1.5 ms for resampling, giving a default delay of 26.5 ms. When the CELT layer is active, it requires 2.5 ms lookahead for window overlap to which a matching delay of 4.0 ms is added by default to synchronize with the SILK layer. If the encoder is instantiated in the special ''restricted low delay'' mode, the 4.0 ms matching delay is removed and the SILK layer is disabled, permitting the minimal algorithmic delay of 5.0 ms.


Support

The format and algorithms are openly documented and the
reference implementation In the software development process, a reference implementation (or, less frequently, sample implementation or model implementation) is a program that implements all requirements from a corresponding specification. The reference implementation o ...
is published as
free software Free software or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software is a matter of liberty, no ...
. Xiph's reference implementation is called ''libopus'' and a package called ''opus-tools'' provides command-line encoder and decoder utilities. It is published under the terms of a BSD-like license. It is written in C and can be compiled for hardware architectures with or without a
floating-point unit In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can be ...
. The accompanying diagnostic tool ''opusinfo'' reports detailed technical information about Opus files, including information on the standard compliance of the bitstream format. It is based on ''ogginfo'' from the ''vorbis-tools'' and therefore — unlike the encoder and decoder — is available under the terms of version 2 of the
GPL The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the four freedoms to run, study, share, and modify the software. The license was the first copyleft for general us ...
.


Implementations

contains a complete source code for an older version of the reference implementation written in C. RFC contains errata. Libopus is the more up-to-date but non-normative branch of the reference implementation. The
FFmpeg FFmpeg is a free and open-source software project consisting of a suite of libraries and programs for handling video, audio, and other multimedia files and streams. At its core is the command-line ffmpeg tool itself, designed for processing of vi ...
project has encoder and decoder implementations not derived from the reference library. The libopus reference library has been ported to both C# and
Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's most ...
as part of a project called Concentus. These ports sacrifice performance for the sake of being easily integrated into cross-platform applications.


Software and content providers

Digital Radio Mondiale Digital Radio Mondiale (DRM; ''mondiale'' being Italian and French for "worldwide") is a set of digital audio broadcasting technologies designed to work over the bands currently used for analogue radio broadcasting including AM broadcasting—p ...
 – a digital radio format for AM frequencies – can broadcast and receive Opus audio (albeit not recognised in official standard) using Dream
software-defined radio Software-defined radio (SDR) is a radio communication system where components that have been traditionally implemented in analog hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented b ...
. The
Wikimedia Foundation The Wikimedia Foundation, Inc., or Wikimedia for short and abbreviated as WMF, is an American 501(c)(3) nonprofit organization headquartered in San Francisco, California and registered as a charitable foundation under local laws. Best know ...
sponsored a free and open source online
JavaScript JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of websites use JavaScript on the client side for webpage behavior, often ...
Opus encoder for browsers supporting the required
HTML5 HTML5 is a markup language used for structuring and presenting content on the World Wide Web. It is the fifth and final major HTML version that is a World Wide Web Consortium (W3C) recommendation. The current specification is known as the HTML ...
features. A list of radio stations that stream using Opus audio codec can be found on the
Xiph.Org Foundation Xiph.Org Foundation is a nonprofit organization that produces free multimedia formats and software tools. It focuses on the Ogg family of formats, the most successful of which has been Vorbis, an open and freely licensed audio format and codec de ...
Icecast Icecast is a streaming media project released as free software maintained by the Xiph.Org Foundation. It also refers specifically to the server program which is part of the project. Icecast was created in December 1998/January 1999 by Jack Mof ...
directory. In late 2014 and 2015, Google's video platform
YouTube YouTube is a global online video sharing and social media platform headquartered in San Bruno, California. It was launched on February 14, 2005, by Steve Chen, Chad Hurley, and Jawed Karim. It is owned by Google, and is the second most vis ...
started offering Opus audio along with
VP9 VP9 is an open and royalty-free video coding format developed by Google. VP9 is the successor to VP8 and competes mainly with MPEG's High Efficiency Video Coding (HEVC/H.265). At first, VP9 was mainly used on Google's video platform YouTube. Th ...
video in the
WebM WebM is an audiovisual media file format. It is primarily intended to offer a royalty-free alternative to use in the HTML5 video and the HTML5 audio elements. It has a sister project, WebP, for images. The development of the format is sponsored ...
file format, through DASH streaming. Since 2016,
WhatsApp WhatsApp (also called WhatsApp Messenger) is an internationally available freeware, cross-platform, centralized instant messaging (IM) and voice-over-IP (VoIP) service owned by American company Meta Platforms (formerly Facebook). It allows u ...
has been using Opus as its audio file format.
Signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...
switched from
Speex Speex is an audio compression codec specifically tuned for the reproduction of human speech and also a free software speech codec that may be used on VoIP applications and podcasts. It is based on the CELP speech coding algorithm.Xiph.OrIntrodu ...
to Opus audio codec for better audio quality in the beginning of 2017. In 2018,
SoundCloud SoundCloud is an online audio distribution platform and music sharing website that enables its users to upload, promote, and share audio. Founded in 2007 by Alexander Ljung and Eric Wahlforss, SoundCloud is one of the largest music streaming se ...
switched from MP3 to Opus, reducing half of its required bandwidth for music streaming. In January 2021,
Vimeo Vimeo, Inc. () is an American video hosting, sharing, and services platform provider headquartered in New York City. Vimeo focuses on the delivery of high-definition video across a range of devices. Vimeo's business model is through software as ...
introduced Opus to its video platform. In 2021, the Danish journalism website Zetland switched from MP3 to Opus for its articles' audio recordings, which attained a 35 percent reduction in bandwidth and reduced climate footprint. One of the changes on VirtualBox 7.0.0 is that Opus was no longer being used.


Operating system support

Most end-user software relies on
multimedia framework A multimedia framework is a software framework that handles media on a computer and through a network. A good multimedia framework offers an intuitive API and a modular architecture to easily add support for new audio, video and container formats ...
s provided by the
operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
. Native Opus codec support is implemented in most major multimedia frameworks for Unix-like operating systems, including
GStreamer GStreamer is a pipeline-based multimedia framework that links together a wide variety of media processing systems to complete complex workflows. For instance, GStreamer can be used to build a system that reads files in one format, processes them, ...
,
FFmpeg FFmpeg is a free and open-source software project consisting of a suite of libraries and programs for handling video, audio, and other multimedia files and streams. At its core is the command-line ffmpeg tool itself, designed for processing of vi ...
, and
Libav Libav is an abandoned free software project, forked from FFmpeg in 2011, that contains libraries and programs for handling multimedia data. History Fork from FFmpeg The Libav project was a fork of the FFmpeg project. It was announced on ...
libraries. The
WebM WebM is an audiovisual media file format. It is primarily intended to offer a royalty-free alternative to use in the HTML5 video and the HTML5 audio elements. It has a sister project, WebP, for images. The development of the format is sponsored ...
container .webm is mostly used on
online video platform An online video platform (OVP), provided by a video hosting service, enables users to upload, convert, store and play back video content on the Internet, often via a structured, large-scale system that may generate revenue. Users will generally u ...
s (e.g.
YouTube YouTube is a global online video sharing and social media platform headquartered in San Bruno, California. It was launched on February 14, 2005, by Steve Chen, Chad Hurley, and Jawed Karim. It is owned by Google, and is the second most vis ...
), and is usually treated as a video file by operating systems & media players. Even if a WebM file contains only Opus audio and no video, some music players do not recognize WebM files as audio files and do not support reading of file metadata. The
Ogg Ogg is a free, open container format maintained by the Xiph.Org Foundation. The authors of the Ogg format state that it is unrestricted by software patents and is designed to provide for efficient streaming and manipulation of high-quality di ...
container .opus is preferred for audio-only files, and most media players have support for audio file metadata tagged in the
Vorbis comment A Vorbis comment is a metadata container used in the Vorbis, FLAC, Theora, Speex and Opus file formats. It allows information such as the title, artist, album, track number or other information about the file to be added to the file itself. Howev ...
format.
Google Google LLC () is an American multinational technology company focusing on search engine technology, online advertising, cloud computing, computer software, quantum computing, e-commerce, artificial intelligence, and consumer electronics. I ...
added native support for Opus audio playback in Android 5.0 "Lollipop". However, it was limited to Opus audio encapsulated in
Matroska Matroska is a project to create a container format that can hold an unlimited number of video, audio, picture, or subtitle tracks in one file. The Matroska Multimedia Container is similar in concept to other containers like AVI, MP4, or Adva ...
and
WebM WebM is an audiovisual media file format. It is primarily intended to offer a royalty-free alternative to use in the HTML5 video and the HTML5 audio elements. It has a sister project, WebP, for images. The development of the format is sponsored ...
containers, such as .mkv, .mka and .webm files. Android 7.0 "Nougat" introduced support for Opus audio encapsulated in
Ogg Ogg is a free, open container format maintained by the Xiph.Org Foundation. The authors of the Ogg format state that it is unrestricted by software patents and is designed to provide for efficient streaming and manipulation of high-quality di ...
containers.
Android 10 Android 10 ( codenamed Android Q during development) is the tenth major release and the 17th version of the Android mobile operating system. It was first released as a developer preview on March 13, 2019, and was released publicly on Septembe ...
finally added native support for .opus
extensions Extension, extend or extended may refer to: Mathematics Logic or set theory * Axiom of extensionality * Extensible cardinal * Extension (model theory) * Extension (predicate logic), the set of tuples of values that satisfy the predicate * E ...
.Support Opus in the MediaScanner (37054258) - Visible to Public - Google Issue Tracker
/ref> Due to the addition of
WebRTC WebRTC (Web Real-Time Communication) is a free and open-source project providing web browsers and mobile applications with real-time communication (RTC) via application programming interfaces (APIs). It allows audio and video communication to wor ...
support in Apple's
WebKit WebKit is a browser engine developed by Apple and primarily used in its Safari web browser, as well as on the iOS and iPadOS version of any web browser. WebKit is also used by the BlackBerry Browser, PlayStation consoles beginning from the PS3 ...
rendering engine,
macOS High Sierra macOS High Sierra (version 10.13) is the fourteenth major release of macOS, Apple Inc.'s desktop operating system for Macintosh computers. macOS High Sierra was announced at the WWDC 2017 on June 5, 2017 and was released on September 25, 2017. ...
and
iOS 11 iOS 11 is the iOS version history, eleventh major release of the iOS mobile operating system developed by Apple Inc., being the successor to iOS 10. It was announced at the company's Apple Worldwide Developers Conference, Worldwide Developers C ...
come with native playback support for Opus audio encapsulated in Core Audio Format containers. On
Windows 10 Windows 10 is a major release of Microsoft's Windows NT operating system. It is the direct successor to Windows 8.1, which was released nearly two years earlier. It was released to manufacturing on July 15, 2015, and later to retail on ...
, version
1607 Events January–June * January 13 – The Bank of Genoa fails, after the announcement of national bankruptcy in Spain. * January 19 – San Agustin Church, Manila, is officially completed; by the 21st century it will be the ...
, Microsoft provided native support for Opus audio encapsulated in
Matroska Matroska is a project to create a container format that can hold an unlimited number of video, audio, picture, or subtitle tracks in one file. The Matroska Multimedia Container is similar in concept to other containers like AVI, MP4, or Adva ...
and
WebM WebM is an audiovisual media file format. It is primarily intended to offer a royalty-free alternative to use in the HTML5 video and the HTML5 audio elements. It has a sister project, WebP, for images. The development of the format is sponsored ...
containers. On version
1709 In the Swedish calendar it was a common year starting on Friday, one day ahead of the Julian and ten days behind the Gregorian calendar. Events January–March * January 1 – Battle of St. John's: The French capture St. John ...
, support for Opus audio encapsulated in
Ogg Ogg is a free, open container format maintained by the Xiph.Org Foundation. The authors of the Ogg format state that it is unrestricted by software patents and is designed to provide for efficient streaming and manipulation of high-quality di ...
containers was made available through a pre-installed add-on called Web Media Extensions. On Windows 10 version
1903 Events January * January 1 – Edward VII is proclaimed Emperor of India. * January 19 – The first west–east transatlantic radio broadcast is made from the United States to England (the first east–west broadcast having been ...
, native support for the .opus extension was added. On
Windows 8.1 Windows 8.1 is a release of the Windows NT operating system developed by Microsoft. It was released to manufacturing on August 27, 2013, and broadly released for retail sale on October 17, 2013, about a year after the retail release of its pre ...
and older, third-party decoders, such as
LAV Filters FFmpeg is a free and open-source software project consisting of a suite of libraries and programs for handling video, audio, and other multimedia files and streams. At its core is the command-line ffmpeg tool itself, designed for processing of vi ...
, are available to provide support for the format.


Media player support

While support in multimedia frameworks automatically enables Opus support in software which is built on top of such frameworks, several applications developers made additional efforts for supporting the Opus audio format in their software. Such support was added to AIMP, Amarok, cmus,
Music Player Daemon Music Player Daemon (MPD) is a free and open music player server. It plays audio files, organizes playlists and maintains a music database. In order to interact with it, a client program is needed. The MPD distribution includes mpc, a simple comm ...
,
foobar2000 foobar2000 (often abbreviated as fb2k or f2k) is a freeware audio player for Microsoft Windows, iOS and Android developed by Peter Pawłowski. It has a modular design, which provides user flexibility in configuration and customization. Stand ...
, Mpxplay,
MusicBee MusicBee is a freeware media player for playback and organization of audio files on Microsoft Windows, built using the audio library. Features * Audio playback: MP3, AAC, M4A, MPC, OGG, FLAC, ALAC, APE, Opus, , WavPack, WMA, WAV, MIDI, ...
,
SMplayer SMPlayer is a cross-platform graphical front-end for MPlayer and mpv and forks of Mplayer using GUI widgets offered by Qt. SMPlayer is free and open-source software subject to the terms of the GNU General Public License version 2 or later. SMpl ...
,
VLC media player VLC media player (previously the VideoLAN Client and commonly known as simply VLC) is a free and open-source, portable, cross-platform media player software and streaming media server developed by the VideoLAN project. VLC is available for de ...
,
Winamp Winamp is a media player (software), media player for Microsoft Windows originally developed by Justin Frankel and Dmitry Boldyrev by their company Nullsoft, which they later sold to AOL in 1999 for $80 million. It was then acquired by Rad ...
and
Xmplay XMPlay is a freeware audio player for Windows. Initially released in 1998, it is often used as a reference player for tracker audio files. Overview Developed by ''Un4seen Developments'' in 1998, it originally only supported the XM file form ...
audio players;
Icecast Icecast is a streaming media project released as free software maintained by the Xiph.Org Foundation. It also refers specifically to the server program which is part of the project. Icecast was created in December 1998/January 1999 by Jack Mof ...
,
Airtime (software) Airtime is a radio management application for remote broadcast automation (via web-based scheduler), and program exchange between radio stations. Airtime was developed and released as free and open-source software, subject to the requirements of ...
audio streaming software; and Asunder audio CD ripper,
CDBurnerXP CDBurnerXP is an optical disc authoring utility for Windows 2000 and later, written mostly in Visual Basic .NET as of version 4, released in September 2007. It has international language support. The software is available to download in both 32 ...
CD burner, FFmpeg, Libav and
MediaCoder __NOTOC__ MediaCoder is a proprietary transcoding program for Microsoft Windows, developed by Stanley Huang since 2005. Features MediaCoder uses various open-source (and several proprietary) audio and video codecs to transcode media files to dif ...
media encoding tools. Streaming Icecast radio trials are live since September 2012 and January 2013.
SteamOS SteamOS is a Linux distribution developed by Valve. It is open source with some closed source components and is the primary operating system for Steam Machines and the Steam Deck. The initial versions of SteamOS, versions 1.0 and 2.0, were ba ...
uses Opus or Vorbis for streaming audio.


Browser support

Opus support is mandatory for
WebRTC WebRTC (Web Real-Time Communication) is a free and open-source project providing web browsers and mobile applications with real-time communication (RTC) via application programming interfaces (APIs). It allows audio and video communication to wor ...
implementations. Opus is supported in
Mozilla Firefox Mozilla Firefox, or simply Firefox, is a free and open-source web browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation. It uses the Gecko rendering engine to display web pages, which implements current an ...
,
Chromium Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal. Chromium metal is valued for its high corrosion resistance and hardne ...
and
Google Chrome Google Chrome is a cross-platform web browser developed by Google. It was first released in 2008 for Microsoft Windows, built with free software components from Apple WebKit and Mozilla Firefox. Versions were later released for Linux, macOS, ...
,
Blink Blinking is a bodily function; it is a semi-autonomic rapid closing of the eyelid. A single blink is determined by the forceful closing of the eyelid or inactivation of the levator palpebrae superioris and the activation of the palpebral portio ...
-based
Opera Opera is a form of theatre in which music is a fundamental component and dramatic roles are taken by singers. Such a "work" (the literal translation of the Italian word "opera") is typically a collaboration between a composer and a libre ...
, as well as all browsers for Unix-like systems relying on
GStreamer GStreamer is a pipeline-based multimedia framework that links together a wide variety of media processing systems to complete complex workflows. For instance, GStreamer can be used to build a system that reads files in one format, processes them, ...
for multimedia formats support. Although
Internet Explorer Internet Explorer (formerly Microsoft Internet Explorer and Windows Internet Explorer, commonly abbreviated IE or MSIE) is a series of graphical user interface, graphical web browsers developed by Microsoft which was used in the Microsoft Wind ...
will not provide Opus playback natively, support for the format is built into the
Edge browser Microsoft Edge is a proprietary, cross-platform web browser created by Microsoft. It was first released in 2015 as part of Windows 10 and Xbox One and later ported to other platforms as a fork of Google's Chromium open-source project: Androi ...
, along with
VP9 VP9 is an open and royalty-free video coding format developed by Google. VP9 is the successor to VP8 and competes mainly with MPEG's High Efficiency Video Coding (HEVC/H.265). At first, VP9 was mainly used on Google's video platform YouTube. Th ...
, for full
WebM WebM is an audiovisual media file format. It is primarily intended to offer a royalty-free alternative to use in the HTML5 video and the HTML5 audio elements. It has a sister project, WebP, for images. The development of the format is sponsored ...
support. Safari supports Opus as of iOS 11 and macOS High Sierra.


VoIP support

Due to its abilities, Opus gained early interest from
voice over IP Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet ...
(VoIP) software vendors. Several SIP clients, including Acrobits Softphone, CSipSimple (via additional plug-in),
Empathy Empathy is the capacity to understand or feel what another person is experiencing from within their frame of reference, that is, the capacity to place oneself in another's position. Definitions of empathy encompass a broad range of social, cog ...
(via GStreamer),
Jitsi Jitsi is a collection of free and open-source multiplatform voice (VoIP), video conferencing and instant messaging applications for the web platform, Windows, Linux, macOS, iOS and Android. The Jitsi project began with the Jitsi Desktop (previous ...
,
Tuenti Tuenti Technologies, S.L.U is a mobile virtual network operator (MVNO) that operates with the Tuenti brand owned by Telefónica. It is a Spain-based tech company that focuses on providing a cloud-based services through its own application and i ...
, Line2 (currently only on
iOS iOS (formerly iPhone OS) is a mobile operating system created and developed by Apple Inc. exclusively for its hardware. It is the operating system that powers many of the company's mobile devices, including the iPhone; the term also includes ...
),
Linphone __NOTOC__ Linphone (contraction of ''Linux phone'') is a free voice over IP softphone, SIP client and service. It may be used for audio and video direct calls and calls through any VoIP softswitch or IP-PBX. Linphone also provides the possibili ...
, Phoner and PhonerLite, SFLphone,
Telephone A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most efficiently the human voice, into el ...
, Mumble,
Discord Discord is a VoIP and instant messaging social platform. Users have the ability to communicate with voice calls, video calls, text messaging, media and files in private chats or as part of communities called "servers".The developer documenta ...
and TeamSpeak 3 voice chat software also support Opus. TrueConf supports Opus in its VoIP products.
Asterisk The asterisk ( ), from Late Latin , from Ancient Greek , ''asteriskos'', "little star", is a typographical symbol. It is so called because it resembles a conventional image of a heraldic star. Computer scientists and mathematicians often v ...
lacked builtin Opus support for legal reasons, but a third-party patch was available for download and official support via a binary blob was added in September 2016. Tox P2P videoconferencing software uses Opus exclusively. Classified-ads distributed messaging app sends raw opus frames inside TLS socket in its VoIP implementation. Opus is widely used as the
voice codec Speech coding is an application of data compression of digital audio signals containing speech. Speech coding uses speech-specific parameter estimation using audio signal processing techniques to model the speech signal, combined with generic da ...
in
WhatsApp WhatsApp (also called WhatsApp Messenger) is an internationally available freeware, cross-platform, centralized instant messaging (IM) and voice-over-IP (VoIP) service owned by American company Meta Platforms (formerly Facebook). It allows u ...
, which has over 1.5billion users worldwide. WhatsApp uses Opus at 816
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...
sampling rate In signal processing, sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave to a sequence of "samples". A sample is a value of the signal at a point in time and/or spa ...
s, with the
Real-time Transport Protocol The Real-time Transport Protocol (RTP) is a network protocol for delivering audio and video over IP networks. RTP is used in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applicati ...
(RTP). The
PlayStation 4 The PlayStation 4 (PS4) is a home video game console developed by Sony Interactive Entertainment. Announced as the successor to the PlayStation 3 in February 2013, it was launched on November 15, 2013, in North America, November 29, 2013 in ...
video game console also uses the CELT/Opus codec for its
PlayStation Network PlayStation Network (PSN) is a digital media entertainment service provided by Sony Interactive Entertainment. Launched in November 2006, PSN was originally conceived for the PlayStation video game consoles, but soon extended to encompass smartp ...
system party chat. It is also used in the Zoom videoconferencing app.


Hardware

Since version 3.13,
Rockbox Rockbox is a free and open-source software replacement for the OEM firmware in various forms of digital audio players (DAPs) with an original kernel. It offers an alternative to the player's operating system, in many cases without removing the or ...
enables Opus playback on supported
portable media players A portable media player (PMP) (also including the related digital audio player (DAP)) is a portable consumer electronics device capable of storing and playing digital media such as audio, images, and video files. The data is typically stored o ...
, including some products from the
iPod The iPod is a discontinued series of portable media players and multi-purpose mobile devices designed and marketed by Apple Inc. The first version was released on October 23, 2001, about months after the Macintosh version of iTunes wa ...
series by Apple, devices made by iriver,
Archos Archos (, stylized as ARCHOS) is a French multinational electronics company that was established in 1988 by Henri Crohas. Archos manufactures tablets, smartphones, portable media players and portable data storage devices. The name is an anagram ...
and
Sandisk SanDisk is a brand for flash memory products, including memory cards and readers, USB flash drives, solid-state drives, and digital audio players, manufactured and marketed by Western Digital. The original company, SanDisk Corporation was acquir ...
, and on Android devices using "Rockbox as an Application". All recent Grandstream
IP phone A VoIP phone or IP phone uses voice over IP technologies for placing and transmitting telephone calls over an IP network, such as the Internet. This is in contrast to a standard phone which uses the traditional public switched telephone networ ...
s support Opus audio both for encoding and decoding. OBihai OBi1062, OBi1032 and OBi1022
IP phone A VoIP phone or IP phone uses voice over IP technologies for placing and transmitting telephone calls over an IP network, such as the Internet. This is in contrast to a standard phone which uses the traditional public switched telephone networ ...
s all support Opus. Recent BlueSound wireless speakers support Opus playback. Devices running Hiby OS, like the Hiby R3, are capable of decoding Opus files natively. Many broadcast IP codecs include Opus such as those manufactured by
Comrex Comrex is an American corporation that designs and manufactures equipment for radio and television broadcasting. Beginnings Comrex was founded in 1961 by John Cheney, a broadcast engineer. His mission, as outlined in Comrex's inaugural press ...
,
GatesAir GatesAir is an American electronics manufacturer that produces, markets and services terrestrial TV and radio broadcast equipment globally. Products and Services GatesAir manufactures transmitters and associated broadcast gear for over-the-air ...
and
Tieline Tieline Technology has offices in Indianapolis in the United States (Tieline America LLC) and in Perth, Western Australia (Tieline Pty Ltd). The company has a wide and established distribution network throughout Europe, the Americas and Austral ...
. The
Sony , commonly stylized as SONY, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan. As a major technology company, it operates as one of the world's largest manufacturers of consumer and professional ...
PlayStation 5 The PlayStation 5 (PS5) is a home video game console developed by Sony Interactive Entertainment. Announced as the successor to the PlayStation 4 in April 2019, it was launched on November 12, 2020, in Australia, Japan, New Zealand, North Ame ...
supports capturing 1080p and 2160p footage using VP9 video and Opus audio in a WebM container.


Patent Claims

As an open standard, the algorithms are openly documented, and a
reference implementation In the software development process, a reference implementation (or, less frequently, sample implementation or model implementation) is a program that implements all requirements from a corresponding specification. The reference implementation o ...
(including the
source code In computing, source code, or simply code, is any collection of code, with or without comments, written using a human-readable programming language, usually as plain text. The source code of a program is specially designed to facilitate the w ...
) is published.
Broadcom Broadcom Inc. is an American designer, developer, manufacturer and global supplier of a wide range of semiconductor and infrastructure software products. Broadcom's product offerings serve the data center, networking, software, broadband, wirel ...
and the Xiph.Org Foundation own
software patent A software patent is a patent on a piece of software, such as a computer program, libraries, user interface, or algorithm. Background A patent is a set of exclusionary rights granted by a state to a patent holder for a limited period of time, ...
s on some of the CELT algorithms, and
Skype Technologies Skype Technologies S.A.R.L (also known as Skype Software S.A.R.L, Skype Communications S.A.R.L, Skype Inc., and Skype Limited) is a Luxembourgish telecommunications company headquartered in Luxembourg City, Luxembourg, whose chief business is th ...
/Microsoft own some on the SILK algorithms; each offers a royalty-free perpetual for use with Opus, reserving only the right to make use of their patents to defend against infringement suits of third parties.
Qualcomm Qualcomm () is an American multinational corporation headquartered in San Diego, California, and incorporated in Delaware. It creates semiconductors, software, and services related to wireless technology. It owns patents critical to the 5G, 4 ...
,
Huawei Huawei Technologies Co., Ltd. ( ; ) is a Chinese multinational technology corporation headquartered in Shenzhen, Guangdong, China. It designs, develops, produces and sells telecommunications equipment, consumer electronics and various smart ...
,
France Telecom Orange S.A. (), formerly France Télécom S.A. (stylized as france telecom) is a French multinational corporation, multinational telecommunications corporation. It has 266 million customers worldwide and employs 89,000 people in France, and 5 ...
, and
Ericsson (lit. "Telephone Stock Company of LM Ericsson"), commonly known as Ericsson, is a Swedish multinational networking and telecommunications company headquartered in Stockholm. The company sells infrastructure, software, and services in informa ...
have claimed that their patents may apply, which Xiph's legal counsel denies, and none have pursued any legal action. The Opus license automatically and retroactively terminates for any entity that attempts to file a patent suit. In September of 2022, UK-based Vectis IP Ltd announced the formation of a patent pool for Opus. Members of the pools included Dolby International AB, Dolby Laboratories Licensing Corporation, and Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. A list of patents will be published soon after an evaluation. However, the program makes an exception for open-source software, applications, or content that developers or providers distribute separate from hardware devices (i.e. PCs, smartphones, IP phones, smart TVs).


Notes


References


Citations


Sources

* This article contains quotations from the Opus Codec website, which is available under th
Creative Commons Attribution 3.0 (CC BY 3.0)
license.


External links

*
Opus on Hydrogenaudio Knowledgebase


See also

*
Comparison of audio coding formats The following tables compare general and technical information for a variety of audio coding formats. For listening tests comparing the perceived audio quality of audio formats and codecs, see the article Codec listening test. General informatio ...
* Streaming media *
xHE-AAC Unified Speech and Audio Coding (USAC) is an audio compression format and codec for both music and speech or any mix of speech and audio using very low bit rates between 12 and 64 kbit/s. It was developed by Moving Picture Experts Group (MPEG ...
{{Compression software Speech codecs Free audio codecs Lossy compression algorithms Xiph.Org projects Software using the BSD license Open formats