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Opus (audio format)

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Opus
Filename extension
.opus[1]
Internet media typeaudio/ogg[2]
audio/opus (RTP)[3]
Developed byIETF codec working group
Initial releaseSeptember 11, 2012; 12 years ago (2012-09-11)
Type of formatLossy audio
Contained byOgg, Matroska, WebM, MPEG-TS, ISOBMFF, CAF
Extended fromSILK, CELT
StandardRFC 6716
Open format?Yes
Free format?Yes
Websiteopus-codec.org
libopus
Developer(s)Xiph.Org Foundation
Initial releaseAugust 26, 2012 (2012-08-26)
Stable release
1.5.2 / April 12, 2024; 8 months ago (2024-04-12)
Written inC89
PlatformCross-platform
TypeAudio codec, reference implementation
License3-clause BSD license plus patent license Opus License
WebsiteOpus codec downloads

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.[4][5] 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.[6][7]

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.[4] 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)[8] necessary for use as part of a real-time communication link, 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.[9]

As an open format standardized through RFC 6716, a reference implementation called libopus is available under the New BSD License. The reference has both fixed-point and floating-point optimizations for low- and high-end devices, with SIMD optimizations on platforms that support them. All known software patents that cover Opus are licensed under royalty-free terms.[10] Opus is widely used as a voice over IP (VoIP) codec in applications such as Discord,[11] WhatsApp,[12][13][14] and the PlayStation 4.[15]

Features

[edit]
Possible bitrate and latency combinations compared with other audio formats

Opus supports constant and variable bitrate 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 rates from 8 kHz (with 4 kHz bandwidth) to 48 kHz (with 20 kHz bandwidth, the human hearing range). 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, Voice over IP and videoconferencing; research by Xiph led to the CELT 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.

Spectrogram of Opus-encoded (~1.0) audio as bitrate rises (~32 to ~160 kbit/s) clearly shows lowpass behavior and better preservation of the band energy with CELT (compare original, Vorbis, MP3, AAC).

The Opus format is based on a combination of the full-bandwidth CELT format and the speech-oriented SILK format, both heavily modified: CELT is based on the modified discrete cosine transform (MDCT) that most music codecs use, using CELP techniques in the frequency domain for better prediction, while SILK uses linear predictive coding (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 Bitrate 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.[16] 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, although floating-point is currently required for audio bandwidth detection (dynamic switching between SILK, CELT, and hybrid encoding) and most speed optimizations.

Containers

[edit]

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. Opus was originally specified for encapsulation in Ogg containers, specified as audio/ogg; codecs=opus, and for Ogg Opus files the .opus filename extension is recommended.[2] Opus streams are also supported in Matroska,[17] WebM,[18] MPEG-TS,[19] and MP4.[20]

Alternatively, each Opus packet may be wrapped in a network packet which supplies the packet length. Opus packets may be sent over an ordered datagram protocol such as RTP.[21]

An optional self-delimited packet format is defined in an appendix to the specification.[22] 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

[edit]
See also: Wideband audio

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.[23]

Abbreviation Audio
bandwidth 		Effective
sample rate
NB (narrowband) 04 kHz 08 kHz
MB (medium-band)[note 1] 06 kHz 12 kHz
WB (wideband) 08 kHz 16 kHz
SWB (super-wideband) 12 kHz 24 kHz
FB (fullband)[note 2] 20 kHz 48 kHz

History

[edit]
See also: CELT § History, and SILK § 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. It is based on two initially separate standard proposals from the Xiph.Org Foundation and Skype Technologies S.A. (now Microsoft). Its main developers are Jean-Marc Valin (Xiph.Org, Octasic, Mozilla Corporation, Amazon), Koen Vos (Skype), and Timothy B. Terriberry (Xiph.Org, Mozilla Corporation, Amazon). Among others, Juin-Hwey (Raymond) Chen (Broadcom), Gregory Maxwell (Xiph.Org, Wikimedia), and Chris Montgomery (Xiph.Org) were also involved.

The development of the CELT part of the format goes back to thoughts on a successor for Vorbis under the working name Ghost. As a newer speech codec from the Xiph.Org Foundation, Opus replaces Xiph's older speech codec Speex, 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 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.[24] Representatives of several companies which were taking part in the standardization of patent-encumbered competing format, including Polycom and Ericsson—the creators and licensors of G.719—as well as France Télécom, Huawei and the Orange Labs (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.)[25] 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.[26] At the beginning of February 2011, the bitstream format was tentatively frozen, subject to last changes.[27] Near the end of July 2011, Jean-Marc Valin was hired by the Mozilla Corporation to continue working on Opus.[28]

Finalization (1.0)

[edit]

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.[29] On July 2, 2012, Opus was approved by the IETF for standardization.[30] The reference software entered release candidate state on August 8, 2012.[31] The final specification was released as RFC 6716 on September 10, 2012.[32][33] and versions 1.0 and 1.0.1 of the reference implementation libopus were released the day after.

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.[34]

1.1

[edit]

On December 5, 2013, libopus 1.1 was released,[34] incorporating overall speed improvements and significant encoder quality improvements: Tonality estimation boosts bitrate and quality for previously 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 work.

1.2

[edit]

libopus 1.2 Beta was released on May 24, 2017. libopus 1.2 was released on June 20, 2017.[35] Improvements brought in 1.2 allow it to create fullband music at bitrates as low as 32 kbit/s, and wideband speech at just 12 kbit/s.[36]

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.[37]

1.3

[edit]

libopus 1.3 was released on October 18, 2018.[38] The Opus 1.3 major release again brings quality improvements, new features, and bug fixes.[39] 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

[edit]

libopus 1.3.1 was released on April 12, 2019.[40] This Opus 1.3.1 minor release fixes an issue with the analysis on files with digital silence (all zeros), especially on x87 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 build system will stay)

1.4

[edit]

libopus 1.4 was released on April 20, 2023.[41] Opus 1.4 brings the following improvements and fixes:

  • Improved tuning of the Opus in-band FEC called LBRR (Low-bitrate redundancy)[42] which previously was causing a significant drop in audio quality under certain circumstances[43]
  • Added a OPUS_SET_INBAND_FEC(2) option that turns on FEC, but does not force SILK mode (FEC will be disabled in CELT mode)
  • Improved tuning and various fixes to DTX
  • Added Meson support, improved CMake support

1.5

[edit]

libopus 1.5 was released on March 4, 2024.[44] It added the following backward-compatible improvements:

  • Improved packet loss concealment using a deep neural network.
  • Improved redundancy to prevent packet loss using a rate-distortion-optimized variational autoencoder.
  • Improved concealment of coding artifacts by adjusting post-filter coefficients using a deep neural network.
  • Support for additional SIMD CPU instructions; AVX2 on x86-64 and NEON on Aarch64.

Current development

[edit]

The codec is under active development.[45] The current focus is on adding a deep learning based redundancy encoder that enhances packet loss concealment by embedding one second of recovery data in each encoded packet. The deep redundancy (DRED) algorithm was developed by among others Jean-Marc Valin, Ahmed Mustafa, Jan Büthe, Timothy Terriberry, Chris Montgomery, Michael Klingbeil, and Paris Smaragdis from Amazon Web Services[46] with sponsorship to open source the algorithm and subsequently extend the IETF standard from Sid Rao.[47] This encoder is a backwards compatible change to the codec enabling customers to easily upgrade applications to take advantage of this machine learning capability. A draft RFC is underway to standardize the new capability.[48] This RFC is one of the first attempts to standardize a deep learning algorithm in the IETF.

Quality comparison and low-latency performance

[edit]
Comparison of coding efficiency between Opus and other popular audio formats

Opus performs well at both low and high bitrates.[9]

Comparison between MP3 and Opus
The first is an uncompressed WAV file, the second is an MP3 file encoded at 16 kbit/s using LAME, and the third is an Opus file encoded at 16 kbit/s.
Problems playing this file? See media help.

In listening tests around 64 kbit/s, Opus shows superior quality compared to HE-AAC codecs, which were previously dominant due to their use of the patented spectral band replication (SBR) technology.[49][6] In listening tests around 96 kbit/s, Opus shows slightly superior quality compared to AAC and significantly better quality compared to Vorbis and MP3.[7][50]

Opus has very low algorithmic delay,[4] a necessity for use as part of a low-audio-latency communication link, which can permit natural conversation, networked music performances, or lip sync 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.[51]

Total one-way latency below 150 ms is the preferred target of most VoIP systems,[52] to enable natural conversation with turn-taking little affected by delay. Musicians typically feel in-time with up to around 30 ms audio latency,[53] roughly in accord with the fusion time of the Haas effect, though matching playback delay of each user's own instrument to the round-trip latency can also help.[54] It is suggested for lip sync that around 45–100 ms audio latency may be acceptable.[55]

Opus permits trading-off reduced quality or increased bitrate to achieve an even smaller algorithmic delay (5.0 ms minimum).[56] 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.[8]

Support

[edit]

The format and algorithms are openly documented and the reference implementation is published as free software. 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. 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.

Implementations

[edit]

RFC 6716 contains a complete source code for an older version of the reference implementation written in C. RFC 8251 contains errata. Libopus is the more up-to-date but non-normative branch of the reference implementation.

The FFmpeg project[57] has encoder and decoder implementations not derived from the reference library. The documentation describes it as CELT-only and poorer-quality than the reference.[58]

The libopus reference library has been ported to both C# and Java as part of a project called Concentus. These ports sacrifice performance for the sake of being easily integrated into cross-platform applications.[59]

Software and content providers

[edit]
See also: Comparison of VoIP software

Digital Radio Mondiale – a digital radio format for AM frequencies – can broadcast and receive Opus audio (albeit not recognised in official standard) using Dream software-defined radio.

The Wikimedia Foundation sponsored a free and open source online JavaScript Opus encoder for browsers supporting the required HTML5 features.[60]

A list of radio stations that stream using Opus audio codec can be found on the Xiph.Org Foundation Icecast directory.[61]

In late 2014 and 2015, Google's video platform YouTube started offering Opus audio along with VP9 video in the WebM file format, through DASH streaming.[62] In July 2024, YouTube rolled out an additional high quality audio format option, 256 kbit/s Opus, to YouTube Music Premium subscribers.[63]

Since 2016, WhatsApp has been using Opus as its audio file format.[64]

Signal switched from Speex to Opus audio codec for better audio quality in the beginning of 2017.

In 2018, SoundCloud switched from MP3 to Opus, reducing half of its required bandwidth for music streaming.[65]

In January 2021, Vimeo introduced Opus to its video platform.[66]

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.[67][68]

Operating system support

[edit]

Most end-user software relies on multimedia frameworks provided by the operating system. Native Opus codec support is implemented in most major multimedia frameworks for Unix-like operating systems, including GStreamer, FFmpeg, and Libav libraries.[69][70][71]

The WebM container .webm is mostly used on online video platforms (e.g. YouTube), 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.[72]

The Ogg container .opus is preferred for audio-only files, and most media players have support for audio file metadata tagged in the Vorbis comment format.

Google added native support for Opus audio playback in Android 5.0 "Lollipop".[73] However, it was limited to Opus audio encapsulated in Matroska and WebM containers, such as .mkv, .mka and .webm files.[74][75] Android 7.0 "Nougat" introduced support for Opus audio encapsulated in Ogg containers.[76] Android 10 finally added native support for .opus extensions.[77]

Due to the addition of WebRTC support in Apple's WebKit rendering engine, macOS High Sierra and iOS 11 were released with native playback support for Opus audio encapsulated in Core Audio Format containers.[78] macOS Sonoma added support for mono and stereo Opus audio encapsulated in MPEG-4 and WebM containers in Safari.[79][80]

On Windows 10, version 1607, Microsoft provided native support for Opus audio encapsulated in Matroska and WebM containers.[81] On version 1709, support for Opus audio encapsulated in Ogg containers was made available through a pre-installed add-on called Web Media Extensions.[82] On Windows 10 version 1903, native support for the .opus extension was added.[77] On Windows 8.1 and older, third-party decoders, such as LAV Filters, are available to provide support for the format.[83] A January 2024 update for Windows 10 & 11 caused File Explorer to freeze up when renaming or deleting Ogg files (including .oga, .ogg, .ogm, .ogv, .ogx, .opus), due to bugs involving the MF Media Source Pack Property Handler shell extension by Microsoft and the Web Media Extensions package in Windows, which were not patched before the Windows Updates were rolled out.[84]

iOS 17 includes support for natively encoding and decoding the Opus codec through the operating system's AudioToolbox framework. Playback of Ogg files in the .opus container is supported through the Files application. Opus is additionally supported within the Core Audio Format .caf container, the QuickTime .mov container, and the ISOBMFF or MP4 file format .mp4 container.[note 3] As the AudioToolbox framework is shared with macOS, similar support should be present in both operating systems as they further develop.[86]

Opus support by different operating systems
Windows macOS Linux Android iOS
Codec support Yes
Partial: Win 10 v1607, 1709, 1809
Full: Win 10 v1903 		Yes
Partial: macOS High Sierra (10.13)
Full: macOS Sonoma (14.0) 		Yes Yes
Partial: Android 5, 6, 7
Full: Android 10 		Yes
Partial: iOS 11
Full: iOS 17
Container support On Windows 10 Anniversary Update (1607):
WebM (.webm is not recognised; requires pseudo extension)
Matroska (.mka, .mkv)

On Windows 10 Fall Creators Update (1709) with Web Media Extensions add-on:
Ogg (.opus is not recognised; requires pseudo extension)[note 4]

On Windows 10 October 2018 Update (1809):
WebM (.webm is recognised officially)

On Windows 10 May 2019 Update (1903):
Ogg (.opus, .oga, .ogg) (.opus is recognised officially)

 On macOS High Sierra:
Core Audio Format (.caf)

On macOS Monterey:
WebM (.webm; experimental support)[88][89]

On macOS Sonoma:
mono and stereo MPEG-4 and WebM (.webm)[79][80]

 Ogg (.opus)
WebM (.webm)
Matroska (.mka, .mkv)
MPEG-TS (.ts) 		On Android 5:
WebM (.webm)
Matroska (.mka, .mkv)

On Android 7:
Ogg (.oga, .ogg) (.opus is not recognised; requires pseudo extension)[note 4]

On Android 10:
Ogg (.opus, .oga, .ogg) (.opus is recognised officially)
MP4 (.mp4) (together with AV1 video)

 On iOS 17 and later:
Supports playback through Files; supports Ogg as .opus; supported in MP4, standalone[note 3] or in combination with any officially supported video codec; standalone and expanded but unofficially supported combinations in MOV; standalone support in CAF
Notes

On Windows 10 & Windows 11:
- As of June 2023, Windows Media Player (2022) does not support Opus audio tracks that accompany videos in MP4 containers.[90]

On Windows 10:
- On Anniversary Update (1607), limited support is available in Microsoft Edge (via MSE only) and Universal Windows Platform apps. Windows Media Player does not support Ogg; only WebM and Matroska.
- On April 2018 Update (1803) with Web Media Extensions preinstalled, Microsoft Edge (EdgeHTML 17) supports Opus audio embedded in <audio> tags.
- Up till October 2018 update (1809), the filename extension .opus was not recognised. (substitute with a pseudo file extension such as .m4a)[87]

On Windows 8.1 and older:
- Requires installation of a third-party multimedia framework, LAV Filters.

 In Safari 15, Apple added support for Opus audio in WebM containers. Experimental support is only present in macOS.[91]

 – - Up till Android 9, the filename extension .opus was not recognised (substitute with a pseudo file extension such as .ogg or .m4a)[76] - When originally introduced in iOS 11, only constant bitrate Opus audio in a CAF container was supported.

- In Safari 15, Apple added support for Opus audio in WebM containers. However, it is non-functional in iOS 15, as of September 2021.[92]

- In iOS 17, native support for playing variable bitrate multichannel .opus files through Quick Look in the Files app was implemented; the codec is additionally natively supported if encapsulated in ISOBMFF/MP4, CAF, or MOV.

- As of iOS 17, WebM support is present in Safari, but not Files.

- Opus can additionally be utilized within MP4 in combination with any video codec supported by the device.

Media player support

[edit]

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,[93] Amarok,[94] cmus, Music Player Daemon, foobar2000,[95] Mpxplay, MusicBee,[96] SMplayer, VLC media player,[97] Winamp[98] and XMPlay audio players; Icecast,[99] Airtime (software)[100] audio streaming software; and Asunder audio CD ripper, CDBurnerXP CD burner, FFmpeg, Libav and MediaCoder media encoding tools. Streaming Icecast radio trials are live since September 2012 and January 2013.[101][102] SteamOS uses Opus or Vorbis for streaming audio.[103]

Browser support

[edit]

Opus support is mandatory for WebRTC implementations.[104] Opus is supported in Mozilla Firefox,[105] Chromium and Google Chrome,[106] Blink-based Opera,[107][108] as well as all browsers for Unix-like systems relying on GStreamer for multimedia formats support. 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.[109][110] Safari supports Opus as of iOS 11 and macOS High Sierra.[111]

VoIP support

[edit]

Due to its abilities, Opus gained early interest from voice over IP (VoIP) software vendors. Several SIP clients, including Acrobits Softphone, CSipSimple (via additional plug-in), Empathy (via GStreamer), Jitsi,[112] Tuenti,[113] Line2 (currently only on iOS),[114] Linphone,[115] Phoner and PhonerLite,[116] SFLphone,[117] Telephone, Mumble, Discord[11] and TeamSpeak 3 voice chat software also support Opus.[118][119][120] TrueConf supports Opus in its VoIP products.[121] Asterisk lacked builtin Opus support for legal reasons,[122] but a third-party patch was available for download[123] and official support via a binary blob was added in September 2016.[124] Tox P2P videoconferencing software uses Opus exclusively.[125] Classified-ads distributed messaging app sends raw opus frames inside TLS socket in its VoIP implementation.[126]

Opus is widely used as the voice codec in WhatsApp,[12][14][13] which has over 1.5 billion users worldwide.[127] WhatsApp uses Opus at 8–16 kHz sampling rates,[12][13] with the Real-time Transport Protocol (RTP).[14] The PlayStation 4 video game console also uses the CELT/Opus codec for its PlayStation Network system party chat.[15] The Source Engine uses Opus for its voice chat system.[128] It is also used in the Zoom videoconferencing app.[129]

Hardware

[edit]

Since version 3.13, Rockbox enables Opus playback on supported portable media players, including some products from the iPod series by Apple, devices made by iriver, Archos and Sandisk, and on Android devices using "Rockbox as an Application".[130][131] All recent Grandstream IP phones support Opus audio both for encoding and decoding. OBihai OBi1062, OBi1032 and OBi1022 IP phones all support Opus. Recent BlueSound wireless speakers support Opus playback.[132] 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, GatesAir and Tieline.[133]

The Sony PlayStation 5 supports capturing 1080p and 2160p footage using VP9 video and Opus audio in a WebM container.[134][135]

Android 13 supports Opus as a bluetooth headphone (A2DP) codec, motivated by its low latency, which is important for head-tracked spatial audio. Google's Pixel Buds Pro supports this A2DP codec.[136]

Patent claims

[edit]

As an open standard, the algorithms are openly documented, and a reference implementation (including the source code) is published. Broadcom and the Xiph.Org Foundation own software patents on some of the CELT algorithms, and Skype Technologies/Microsoft own some on the SILK algorithms; each offers a royalty-free perpetual license for use with Opus, reserving only the right to make use of their patents to defend against infringement suits of third parties. Qualcomm, Huawei, France Telecom, and Ericsson have claimed that their patents may apply, which Xiph's legal counsel denies, and none have pursued any legal action.[10][137] The Opus license automatically and retroactively terminates for any entity that attempts to file a patent suit.

Notes

[edit]
  1. ^ Unused by default since 1.3.
  2. ^ Opus cuts audio above 20 kHz, the generally accepted upper limit of the human hearing range.
  3. ^ a b Opus will only work standalone on iOS 17 in ISOBMFF/MP4 if its "major version", the container's "brand", or "ftype", is not "M4A ". iOS expects audio files to use the .m4a extension,[85] relegating .mp4 to video, so playback will present a blank video track even if none are present within the container. Re-naming a .mp4 file to .m4a will work as expected, however.
  4. ^ a b On Android 9 and Microsoft Windows 10 (1809), the .opus filename extension isn't recognized by Android's MediaScanner service and Universal Windows Platform apps. A pseudo extension of another audio format (such as .ogg or .m4a) is required to detect and playback files.[76][87]

References

[edit]

Citations

[edit]
  1. ^ "MIME Types and File Extensions". XiphWiki.
  2. ^ a b Terriberry, Timothy; Lee, Ron; Giles, Ralph (April 2016). "Content Type". Ogg Encapsulation for the Opus Audio Codec. IETF. p. 30. sec. 9. doi:10.17487/RFC7845. RFC 7845. Retrieved 2016-04-30.
  3. ^ Spittka, Julian; Vos, Koen; Valin, Jean-Marc (2015-06-30). "Opus Media Type Registration". RTP Payload Format for the Opus Speech and Audio Codec. IETF. p. 9. sec. 6.1. doi:10.17487/RFC7587. ISSN 2070-1721. RFC 7587. Retrieved 2015-06-30.
  4. ^ a b c "Opus Codec". Opus (Home page). Xiph.org Foundation. Retrieved July 31, 2012.
  5. ^ Bright, Peter (2012-09-12). "Newly standardized Opus audio codec fills every role from online chat to music". Ars Technica. Retrieved 2014-05-28.
  6. ^ a b Valin, Jean-Marc; Vos, Koen; Skoglund, Jan (2013-05-17). Hoene, Christian (ed.). "Summary of Opus listening test results". Ietf Datatracker. Internet Engineering Task Force. Archived from the original on 2021-07-24. Retrieved 2021-07-24.
  7. ^ a b Kamedo2 (July 2014). "Results of the public multiformat listening test".{{cite web}}: CS1 maint: numeric names: authors list (link)
  8. ^ a b Jean-Marc Valin; Gregory Maxwell; Timothy B. Terriberry; Koen Vos (October 17–20, 2013). "High-Quality, Low-Delay Music Coding in the Opus Codec" (PDF). www.xiph.org. New York, NY: Xiph.Org Foundation. p. 2. Archived from the original (PDF) on 14 July 2018. Retrieved 19 August 2014. CELT's look-ahead is 2.5 ms, while SILK's look-ahead is 5 ms, plus 1.5 ms for the resampling (including both encoder and decoder resampling). For this reason, the CELT path in the encoder adds a 4 ms delay. However, an application can restrict the encoder to CELT and omit that delay. This reduces the total look-ahead to 2.5 ms.
  9. ^ a b Chen, Raymond (April 1, 2011). "Opus Testing" (PDF). Retrieved 2016-01-02.
  10. ^ a b "Opus Codec License". Xiph.org. Retrieved 2015-12-22.
  11. ^ a b "What Features Does Discord Have?". Discord. Retrieved 2017-10-29.
  12. ^ a b c Leyden, John (27 October 2015). "WhatsApp laid bare: Info-sucking app's innards probed". The Register. Retrieved 19 October 2019.
  13. ^ a b c Srivastava, Saurabh Ranjan; Dube, Sachin; Shrivastaya, Gulshan; Sharma, Kavita (2019). "Smartphone Triggered Security Challenges: Issues, Case Studies and Prevention". In Le, Dac-Nhuong; Kumar, Raghvendra; Mishra, Brojo Kishore; Chatterjee, Jyotir Moy; Khari, Manju (eds.). Cyber Security in Parallel and Distributed Computing: Concepts, Techniques, Applications and Case Studies. John Wiley & Sons. pp. 187–206 (200). doi:10.1002/9781119488330.ch12. ISBN 9781119488057. S2CID 214034702.
  14. ^ a b c Hazra, Sudip; Mateti, Prabhaker (September 13–16, 2017). "Challenges in Android Forensics". In Thampi, Sabu M.; Pérez, Gregorio Martínez; Westphall, Carlos Becker; Hu, Jiankun; Fan, Chun I.; Mármol, Félix Gómez (eds.). Security in Computing and Communications: 5th International Symposium, SSCC 2017. Springer. pp. 286–299 (290). doi:10.1007/978-981-10-6898-0_24. ISBN 9789811068980.
  15. ^ a b "Open Source Software used in PlayStation®4". Sony Interactive Entertainment Inc. Retrieved 2017-12-11.
  16. ^ Montgomery, Christopher (December 23, 2010). "next generation audio: CELT update 20101223".
  17. ^ Bunkus, Moritz (2013-09-16). "MKVToolNix v6.4.0 released". Matroska users (Mailing list). Retrieved 2013-12-24.
  18. ^ "WebM Container Guidelines". The WebM Project. Retrieved 19 October 2015.
  19. ^ "List of Registered MPEG TS Identifiers – SMPTE Registration Authority, LLC". SMPTE. 2019-01-05. Retrieved 2019-01-05.
  20. ^ "Encapsulation of Opus in ISO Base Media File Format". 2018-08-28. Retrieved 2019-01-05.
  21. ^ Spittka, Julian; Vos, Koen; Valin, Jean-Marc (2015-06-30). RTP Payload Format for the Opus Speech and Audio Codec. IETF. doi:10.17487/RFC7587. ISSN 2070-1721. RFC 7587. Retrieved 2019-01-05.
  22. ^ Valin, Jean-Marc; Vos, Koen; Terriberry, Timothy B. (2012-09-11). "Self-Delimiting Framing". Definition of the Opus Audio Codec. IETF. p. 321. sec. B. doi:10.17487/RFC6716. ISSN 2070-1721. RFC 6716. Retrieved 2019-01-05.
  23. ^ Valin, Jean-Marc; Vos, Koen; Terriberry, Timothy B. (2012-09-11). "Opus Codec Overview". Definition of the Opus Audio Codec. p. 8. sec. 2. doi:10.17487/RFC6716. ISSN 2070-1721. RFC 6716. Retrieved 2014-06-21.
  24. ^ "IETF working towards royalty-free audio codec". H-online.com. 2009-11-13. Retrieved 2016-04-07.
  25. ^ "Xiph.org's "Monty" on codecs and patents [LWN.net]". lwn.net.
  26. ^ Vos, Koen (2010-10-15). "Harmony became Opus". codec (Mailing list). IETF. Retrieved 2016-01-03.
  27. ^ "IETF Opus codec now ready for testing". Hydrogenaudio. Retrieved 2012-09-12.
  28. ^ Valin, Jean-Marc (2011-08-01). "IETF update, Mozilla". LiveJournal.com. Retrieved 2012-10-05.
  29. ^ "Opus Codec". Xiph.org Foundation. Retrieved 2012-09-12.
  30. ^ "Opus approved by the IETF". Jmspeex.livejournal.com. 2012-07-03. Retrieved 2012-09-12.
  31. ^ "[opus] Release candidates for 1.0.0 and 1.0.1 are available". opus (Mailing list). Xiph.org Foundation. Retrieved 2012-10-05.
  32. ^ "It's Opus, it rocks and now it's an audio codec standard!". Mozilla Hacks. Retrieved 2012-09-12.
  33. ^ "RFC 6716 on Definition of the Opus Audio Codec". announce (Mailing list). IETF. Retrieved 2012-09-12.
  34. ^ a b Monty; Valin, Jean-Marc. "Opus update 20131205: 1.1 Release". Archived from the original on 2017-04-30. Retrieved 2013-07-17.
  35. ^ "libopus 1.2 – Opus Codec". Opus-codec.org. 2017-06-20. Retrieved 2017-08-23.
  36. ^ Zimmerman, Steven (2017-07-07). "Opus 1.2 Codec Arrives on Your Phone: High Quality Audio at 32 kbps". XDA Developers. Archived from the original on 2017-07-13. Retrieved 2017-07-12.
  37. ^ Valin, Jean-Marc (2017-06-20). "Opus 1.2 released".
  38. ^ "Opus Codec". www.opus-codec.org. Retrieved 2018-10-22.
  39. ^ "Opus 1.3 Released". people.xiph.org. Retrieved 2018-10-22.
  40. ^ "Opus Codec". www.opus-codec.org. Retrieved 2019-04-12.
  41. ^ "Opus release 1.4". GitHub. 2023-04-20.
  42. ^ "Neural encoding enables more-efficient recovery of lost audio packets". 24 March 2023. Retrieved 2023-04-20. Article cited for description of LBRR only. Neural FEC is not part of Opus 1.4.
  43. ^ Danahy, Scott (July 20, 2022). "Subjective Quality Issue: Complexity and FEC".
  44. ^ "Opus 1.5 Released". 2024-03-04. Retrieved 2024-03-04.
  45. ^ "Commits · xiph/opus". GitHub. Retrieved 2024-03-03.
  46. ^ "opus/dnn/README.md at main · xiph/opus". GitHub. Retrieved 2024-03-03.
  47. ^ "RTC @Scale 2023". At Scale Conferences. Retrieved 2024-03-03.
  48. ^ Terriberry, Timothy B.; Valin, Jean-Marc (2023-10-23). Extension Formatting for the Opus Codec (Report). Internet Engineering Task Force.
  49. ^ Next-Gen Low-Latency Open Codec Beats HE-AAC, Slashdot-Meldung vom 14. April 2011.
  50. ^ Maxwell, Gregory (2011). "64kbit/sec stereo multiformat listening test — unofficial results page". Xiph.Org Foundation. Archived from the original on 2012-11-12. Retrieved 2011-06-19.
  51. ^ Lutzky, Manfred; Schuller, Gerald; Gayer, Marc; Krämer, Ulrich; Wabnik, Stefan (2004). "A guideline to audio codec delay" (PDF). In AES 116th Convention, Berlin, Germany: 8–11. Retrieved 21 December 2016.
  52. ^ Lironi, F.; Masseroni, C.; Trivisonno, R.; Ball, C. F. (2005). "Multi RAB-based multimedia services over GERAN mobile networks". VTC-2005-Fall. 2005 IEEE 62nd Vehicular Technology Conference, 2005. Vol. 3. pp. 1662–1666. doi:10.1109/VETECF.2005.1558224. ISBN 0-7803-9152-7. S2CID 44037728.
  53. ^ Lago, Nelson Posse; Kon, Fabio (November 2004). "The quest for low latency". Proceedings of the International Computer Music Conference 2004. pp. 33–36. hdl:2027/spo.bbp2372.2004.142. Retrieved 23 April 2019.
  54. ^ Carôt, Alexander (2010). "Low Latency Audio Streaming for Internet-Based Musical Interaction" in Streaming Media Architectures: Techniques and Applications: Recent Advances. IGI Global. pp. 362–383. ISBN 978-1-61692-833-9.
  55. ^ Ye, Nong; Chen, Yan; Farley, Toni (29–31 May 2003). Qos Requirements Of Multimedia Data On Computer Networks. Proceedings of the Second International Conference on Active Media Technology. Chongqing, PR China: World Scientific Publishing Company Incorporated. pp. 183–189. ISBN 978-981-238-343-3.
  56. ^ Montgomery, Christopher. "A quick showcase of the bleeding edge... CELT 0.10.0 @ constant PEAQ value, varying latency". CELT v0.10 (latest prior to Opus integration). xiph.org. Archived from the original on 23 August 2013. Retrieved 30 October 2012.
  57. ^ Pehlivanov, Rostislav (11 February 2017). "opus: add a native Opus encoder". Git.videolan.org. Retrieved 2017-08-23.
  58. ^ "FFmpeg Codecs Documentation". ffmpeg.org.
  59. ^ "lostromb/concentus: Pure Portable C# and Java implementations of the Opus audio codec". GitHub. Retrieved 2017-08-23.
  60. ^ Rillke, Rainer (2015). "JavaScript opus encoder". Retrieved 2015-02-09.
  61. ^ "Xiph Directory — Codec Opus". Xiph Directory.
  62. ^ "A look into YouTube's video file anatomy". YouTube Engineering and Developers Blog. Archived from the original on 2021-03-08. Retrieved 2022-06-10.
  63. ^ "Youtube Format IDs". GitHub.
  64. ^ Rashad, A. (2017-05-18). "Audio Manager for WhatsApp: How to play WhatsApp audio messages in music player?". Medium. Retrieved 2020-09-09.
  65. ^ "What is Opus? Here's all you need to know about SoundCloud's new audio file format". Fact Magazine. 5 January 2018.
  66. ^ "Introducing Opus, a powerful new audio codec". vimeo blog. 12 January 2021.
  67. ^ "Audio formats and their climate footprint". Sustainable Web. 2 February 2022.
  68. ^ "How a tip from a member made our audio files 35 percent greener". Zetland (in Danish). 25 November 2021.
  69. ^ "GStreamer: news". Gstreamer.freedesktop.org. Retrieved 2012-10-05.
  70. ^ "Audio Codecs". FFmpeg General Documentation. Retrieved 2014-05-28.
  71. ^ "Audio Codecs". Libav General Documentation. Archived from the original on 2014-05-29. Retrieved 2014-05-28.
  72. ^ "Recommended container/extension for opus for tagging compatibility". hydrogenaud.io.
  73. ^ Google. "Android Lollipop". Retrieved 2015-11-03. {{cite web}}: |author= has generic name (help)
  74. ^ "Supported Media Formats". Retrieved 2015-04-29.
  75. ^ Google. "Issue 80729: Opus support not working". Retrieved 2016-04-19. {{cite web}}: |author= has generic name (help)
  76. ^ a b c "Android 7.0 (N) Compatibility Definition". Retrieved 2017-05-22.
  77. ^ a b "Google Issue Tracker". issuetracker.google.com.
  78. ^ iOS 11: Opus support in podcast feeds
  79. ^ a b "Safari 17 Release Notes". Apple Developer.
  80. ^ a b Simmons, Jen (September 18, 2023). "WebKit Features in Safari 17.0". WebKit.
  81. ^ Blog, Microsoft Edge (April 18, 2016). "WebM, VP9 and Opus Support in Microsoft Edge". Microsoft Edge Blog.
  82. ^ Aleksandersen, Daniel (28 December 2021). "Microsoft adds Ogg, Theora, and Vorbis media formats to Windows 10". www.ctrl.blog.
  83. ^ "lavfilters — Open-Source DirectShow Media Splitter and Decoders". Google Project Hosting. Archived from the original on 2013-01-03. Retrieved 2012-10-05.
  84. ^ "ogg files are crashing file explorer in Windows 10". 8 May 2021.
  85. ^ MPEG-4 File Format, Version 2. www.loc.gov (Full draft). Sustainability of Digital Formats. Washington, D.C.: Library of Congress. 25 April 2023. Retrieved 2024-06-23.
  86. ^ "Audio Toolbox". Apple Developer Documentation. Retrieved 2024-06-24.
  87. ^ a b "Supported audio and video formats (Windows Runtime apps) - Windows app development". learn.microsoft.com. 13 October 2015.
  88. ^ Simmons, Jen (October 26, 2021). "New WebKit Features in Safari 15".
  89. ^ "Apple Developer Documentation". developer.apple.com.
  90. ^ "Windows 11's new media player cannot play opus encoded audio in mp4 file - Super User".
  91. ^ "Webに最適なメディアフォーマットを整理する - 2021". Zenn.
  92. ^ Espósito, Filipe (August 10, 2021). "Apple adding WebM audio codec support to Safari with iOS 15". 9To5Mac.
  93. ^ "AIMP: Home Page". Aimp.ru. Retrieved 2012-10-05.
  94. ^ "Amarok 2.8 "Return To The Origin" released". Amarok. 2013-08-16. Retrieved 2014-05-28.
  95. ^ "foobar2000 v1.1.14 beta". Hydrogenaudio Forums. Retrieved 2012-10-05.
  96. ^ "MusicBee". MusicBee Forum. Retrieved 2013-08-17.
  97. ^ "VLC 2.0.4 Twoflower". VideoLAN. Retrieved 2012-10-19.
  98. ^ "Winamp". Winamp Forums. 16 August 2012. Retrieved 2013-01-04.
  99. ^ "Icecast 2.4 beta release". Lists.xiph.org. 17 July 2012. Retrieved 2012-09-12.
  100. ^ Airtime, Changelog. "Airtime/changelog at 2.4.x". Sourcefabric. Retrieved 1 July 2013.
  101. ^ Radio Jackie, Listen Now. "Opus Stream". Radio Jackie. Archived from the original on 12 October 2013. Retrieved 14 May 2013.
  102. ^ Absolute Radio, Listen Labs. "Opus Streaming Trial". Absolute Radio. Retrieved 30 October 2012.
  103. ^ "Steam Beta Update: SteamVR and In-Home Streaming Beta". SteamDB. Retrieved 9 December 2015.
  104. ^ "Zwei Audio-Codecs für Echtzeit-Kommunikation im Browser". Heise.de. 31 July 2012. Retrieved 2012-09-12.
  105. ^ "Media formats supported by the HTML audio and video elements". Developer.mozilla.org. 2012-09-03. Archived from the original on 2010-06-27. Retrieved 2012-09-12.
  106. ^ "Issue 104241: Support OPUS in Ogg files for the audio tag and Audio object". Chromium bug tracker. Retrieved 2014-05-28.
  107. ^ "Why no official mention of Opus support?". My.opera.com. 2012-07-19. Retrieved 2012-09-12.
  108. ^ Shankland, Stephen (2012-08-17). "How corporate bickering hobbled better Web audio". CNET News. Retrieved 2012-09-12.
  109. ^ "Platform status". Microsoft. 2016-04-19.
  110. ^ "WebM, VP9 and Opus Support in Microsoft Edge". Microsoft. 2016-04-18.
  111. ^ "Announcing WebRTC and Media Capture". webkit.org. 7 June 2017. Retrieved 20 June 2017. available on Safari on macOS High Sierra, iOS 11, (…) Safari supports modern audio codecs such as Opus
  112. ^ Bocquet, Ludovic (2013-03-07). "Jitsi 2.0 Now Released!". XMPP Foundation. Archived from the original on 2014-05-29. Retrieved 2014-05-28.
  113. ^ "Tuenti+WebRTC (Voip2day 2014)". 2014-10-21.
  114. ^ "A new Line2 for iOS experience with improved sound quality". Line2. 2012-10-18. Archived from the original on 2013-03-15. Retrieved 2013-03-15.
  115. ^ "Linphone | Linphone". www.linphone.org.
  116. ^ "PhonerLite: configuration". phonerlite.de.
  117. ^ "SFLphone — Task #14602: [Codec] Implement opus". Savoir-faire Linux. 2012-08-13. Archived from the original on 2012-12-17. Retrieved 2012-09-12.
  118. ^ Brandon (2013-06-19). "Mumble 1.2.4 Has been released". Mumblevoice Blog. Archived from the original on 2014-06-28. Retrieved 2014-05-28.
  119. ^ "TeamSpeak 3 Client 3.0.10 released". TeamSpeak Forums. Retrieved 2013-03-04.
  120. ^ "TeamSpeak 3 Server Version 3.0.7 released". TeamSpeak Forums. Retrieved 2013-03-04.
  121. ^ "TrueConf сделал ставку на аудиокодек Opus" [TrueConf opted for Opus audio codec] (Press release) (in Russian). Moscow, Russia. 2012-09-19. Archived from the original on 2014-05-29. Retrieved 2014-05-28.
  122. ^ Jordan, Matthew (2013-05-29). "Opus and VP8". asterisk-dev (Mailing list). Retrieved 2014-05-28.
  123. ^ "Asterisk Opus/VP8 patch". GitHub. Retrieved 2014-05-28.
  124. ^ "Opus for Asterisk". Inside the Asterisk. 2016-09-30. Archived from the original on 2016-10-03. Retrieved 2016-10-03.
  125. ^ "Tox codec handling source code". GitHub. Retrieved 2015-12-09.
  126. ^ "Classified-ads audio encoder documentation". Retrieved 2016-05-25.
  127. ^ Constine, Josh (January 31, 2018). "WhatsApp hits 1.5 billion monthly users. $19B? Not so bad". TechCrunch. Archived from the original on February 9, 2018. Retrieved February 8, 2018.
  128. ^ Li, Zhenyang (2021-03-30). "Reversing Steam Voice Codec". zhenyangli.me. Retrieved 2023-10-22.
  129. ^ "Premium Audio – Integrated Audio Makes Your Meetings Easy" (PDF). Zoom. Retrieved 23 October 2023.
  130. ^ Rockbox Contributors (2013-03-05). "Release notes for Rockbox v.3.13". Rockbox. Retrieved 2013-03-21. {{cite web}}: |author= has generic name (help)
  131. ^ "RockboxAsAnApplication2010 < Main < Wiki". Rockbox.org. Retrieved 2012-10-05.
  132. ^ "PULSE FLEX". BlueSound. Retrieved 28 February 2017.
  133. ^ "Tieline Integrates OPUS into Report-IT and IP codecs". Radio Magazine. 2012-12-18. Archived from the original on 2013-05-09. Retrieved 2012-12-18.
  134. ^ "MLB The Show 20 Gameplay Video - 4K HDR 60 FPS on PlayStation 5, Load Times Also Revealed". 14 November 2020. Retrieved 2021-04-19.
  135. ^ "How to play video and music from discs and USB drives PlayStation (US)". www.playstation.com.
  136. ^ Rahman, Mishaal. "A firmware update is rolling out to the Pixel Buds Pro enabling spatial audio with head tracking. As expected, this uses the Opus codec over BT A2DP to minimize latency". Twitter.
  137. ^ "Nokia's VP8 patent claims: we've been here before". OSNews. 2013-05-25. Retrieved 2014-07-17.

Sources

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Wikimedia Commons has media related to Opus.

See also

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Retrieved from "https://en.wikipedia.org/w/index.php?title=Opus_(audio_format)&oldid=1263213484"