Opus (audio format)
Lossy audio coding format / From Wikipedia, the free encyclopedia
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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]
Filename extension |
.opus[1] |
---|---|
Internet media type | audio/ogg [2]audio/opus (RTP)[3] |
Developed by | IETF codec working group |
Initial release | September 11, 2012; 11 years ago (2012-09-11) |
Type of format | Lossy audio |
Contained by | Ogg, Matroska, WebM, MPEG-TS |
Extended from | SILK, CELT |
Standard | RFC 6716 |
Open format? | Yes |
Free format? | Yes |
Website | opus-codec |
Developer(s) | Xiph.Org Foundation |
---|---|
Initial release | August 26, 2012 (2012-08-26) |
Stable release | 1.5.2
/ April 12, 2024; 4 days ago (2024-04-12) |
Written in | C89 |
Platform | Cross-platform |
Type | Audio codec, reference implementation |
License | 3-clause BSD license |
Website | Opus codec downloads |
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]