RTP Payload Format for the Opus Speech and Audio Codec
RFC 7587

Document Type RFC - Proposed Standard (June 2015; No errata)
Last updated 2015-10-14
Replaces draft-spittka-payload-rtp-opus
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Stream WG state Submitted to IESG for Publication
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IESG IESG state RFC 7587 (Proposed Standard)
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Internet Engineering Task Force (IETF)                        J. Spittka
Request for Comments: 7587
Category: Standards Track                                         K. Vos
ISSN: 2070-1721                                                  vocTone
                                                               JM. Valin
                                                                 Mozilla
                                                               June 2015

         RTP Payload Format for the Opus Speech and Audio Codec

Abstract

   This document defines the Real-time Transport Protocol (RTP) payload
   format for packetization of Opus-encoded speech and audio data
   necessary to integrate the codec in the most compatible way.  It also
   provides an applicability statement for the use of Opus over RTP.
   Further, it describes media type registrations for the RTP payload
   format.

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/rfc7587.

Copyright Notice

   Copyright (c) 2015 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.

Spittka, et al.              Standards Track                    [Page 1]
RFC 7587               RTP Payload Format for Opus             June 2015

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions, Definitions, and Acronyms Used in This Document    3
   3.  Opus Codec  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Network Bandwidth . . . . . . . . . . . . . . . . . . . .   4
       3.1.1.  Recommended Bitrate . . . . . . . . . . . . . . . . .   4
       3.1.2.  Variable versus Constant Bitrate  . . . . . . . . . .   4
       3.1.3.  Discontinuous Transmission (DTX)  . . . . . . . . . .   5
     3.2.  Complexity  . . . . . . . . . . . . . . . . . . . . . . .   6
     3.3.  Forward Error Correction (FEC)  . . . . . . . . . . . . .   6
     3.4.  Stereo Operation  . . . . . . . . . . . . . . . . . . . .   6
   4.  Opus RTP Payload Format . . . . . . . . . . . . . . . . . . .   7
     4.1.  RTP Header Usage  . . . . . . . . . . . . . . . . . . . .   7
     4.2.  Payload Structure . . . . . . . . . . . . . . . . . . . .   7
   5.  Congestion Control  . . . . . . . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     6.1.  Opus Media Type Registration  . . . . . . . . . . . . . .   9
   7.  SDP Considerations  . . . . . . . . . . . . . . . . . . . . .  12
     7.1.  SDP Offer/Answer Considerations . . . . . . . . . . . . .  13
     7.2.  Declarative SDP Considerations for Opus . . . . . . . . .  15
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  16
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  17
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   Opus [RFC6716] is a speech and audio codec developed within the IETF
   Internet Wideband Audio Codec working group.  The codec has a very
   low algorithmic delay, and it is highly scalable in terms of audio
   bandwidth, bitrate, and complexity.  Further, it provides different
   modes to efficiently encode speech signals as well as music signals,
   thus making it the codec of choice for various applications using the
   Internet or similar networks.

   This document defines the Real-time Transport Protocol (RTP)
   [RFC3550] payload format for packetization of Opus-encoded speech and
   audio data necessary to integrate Opus in the most compatible way.
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