Definition of the Opus Audio Codec
RFC 6716
| Document | Type |
RFC - Proposed Standard
(September 2012; Errata)
Updated by RFC 8251
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Replaces | draft-ietf-codec-harmony | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Reviews | |||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Jonathan Rosenberg | ||
| Shepherd write-up | Show (last changed 2012-05-21) | ||
| IESG | IESG state | RFC 6716 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Robert Sparks | ||
| IESG note | Jonathan Rosenberg (jdrosen@jdrosen.net) is the document shepherd. | ||
| Send notices to | (None) | ||
Internet Engineering Task Force (IETF) JM. Valin
Request for Comments: 6716 Mozilla Corporation
Category: Standards Track K. Vos
ISSN: 2070-1721 Skype Technologies S.A.
T. Terriberry
Mozilla Corporation
September 2012
Definition of the Opus Audio Codec
Abstract
This document defines the Opus interactive speech and audio codec.
Opus is designed to handle a wide range of interactive audio
applications, including Voice over IP, videoconferencing, in-game
chat, and even live, distributed music performances. It scales from
low bitrate narrowband speech at 6 kbit/s to very high quality stereo
music at 510 kbit/s. Opus uses both Linear Prediction (LP) and the
Modified Discrete Cosine Transform (MDCT) to achieve good compression
of both speech and music.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6716.
Valin, et al. Standards Track [Page 1]
RFC 6716 Interactive Audio Codec September 2012
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
The licenses granted by the IETF Trust to this RFC under Section 3.c
of the Trust Legal Provisions shall also include the right to extract
text from Sections 1 through 8 and Appendix A and Appendix B of this
RFC and create derivative works from these extracts, and to copy,
publish, display and distribute such derivative works in any medium
and for any purpose, provided that no such derivative work shall be
presented, displayed or published in a manner that states or implies
that it is part of this RFC or any other IETF Document.
Table of Contents
1. Introduction ....................................................5
1.1. Notation and Conventions ...................................6
2. Opus Codec Overview .............................................8
2.1. Control Parameters ........................................10
2.1.1. Bitrate ............................................10
2.1.2. Number of Channels (Mono/Stereo) ...................11
2.1.3. Audio Bandwidth ....................................11
2.1.4. Frame Duration .....................................11
2.1.5. Complexity .........................................11
2.1.6. Packet Loss Resilience .............................12
2.1.7. Forward Error Correction (FEC) .....................12
2.1.8. Constant/Variable Bitrate ..........................12
2.1.9. Discontinuous Transmission (DTX) ...................13
3. Internal Framing ...............................................13
3.1. The TOC Byte ..............................................13
3.2. Frame Packing .............................................16
3.2.1. Frame Length Coding ................................16
3.2.2. Code 0: One Frame in the Packet ....................16
3.2.3. Code 1: Two Frames in the Packet, Each with
Equal Compressed Size ..............................17
3.2.4. Code 2: Two Frames in the Packet, with
Different Compressed Sizes .........................17
Valin, et al. Standards Track [Page 2]
RFC 6716 Interactive Audio Codec September 2012
3.2.5. Code 3: A Signaled Number of Frames in the Packet ..18
3.3. Examples ..................................................21
Show full document text