Ambisonics in an Ogg Opus Container
RFC 8486
| Document | Type |
RFC - Proposed Standard
(October 2018; No errata)
Updates RFC 7845
|
|
|---|---|---|---|
| Last updated | 2018-10-29 | ||
| Replaces | draft-graczyk-codec-ambisonics | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Reviews | |||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Tim Terriberry | ||
| Shepherd write-up | Show (last changed 2018-06-01) | ||
| IESG | IESG state | RFC 8486 (Proposed Standard) | |
| Consensus Boilerplate | Yes | ||
| Telechat date | |||
| Responsible AD | Ben Campbell | ||
| Send notices to | Tim Terriberry <tterriberry@mozilla.com> | ||
| IANA | IANA review state | IANA OK - Actions Needed | |
| IANA action state | RFC-Ed-Ack | ||
Internet Engineering Task Force (IETF) J. Skoglund
Request for Comments: 8486 Google LLC
Updates: 7845 M. Graczyk
Category: Standards Track October 2018
ISSN: 2070-1721
Ambisonics in an Ogg Opus Container
Abstract
This document defines an extension to the Opus audio codec to
encapsulate coded Ambisonics using the Ogg format. It also contains
updates to RFC 7845 to reflect necessary changes in the description
of channel mapping families.
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 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8486.
Copyright Notice
Copyright (c) 2018 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
(https://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.
Skoglund & Graczyk Standards Track [Page 1]
RFC 8486 Opus Ambisonics October 2018
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Ambisonics with Ogg Opus . . . . . . . . . . . . . . . . . . 3
3.1. Channel Mapping Family 2 . . . . . . . . . . . . . . . . 3
3.2. Channel Mapping Family 3 . . . . . . . . . . . . . . . . 4
3.3. Allowed Numbers of Channels . . . . . . . . . . . . . . . 5
4. Downmixing . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Updates to RFC 7845 . . . . . . . . . . . . . . . . . . . . . 7
5.1. Format of the Channel Mapping Table . . . . . . . . . . . 7
5.2. Unknown Mapping Families . . . . . . . . . . . . . . . . 8
6. Experimental Mapping Families . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 10
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
Ambisonics is a representation format for three-dimensional sound
fields that can be used for surround sound and immersive virtual-
reality playback. See [fellgett75] and [daniel04] for technical
details on the Ambisonics format. For the purposes of the this
document, Ambisonics can be considered a multichannel audio stream.
A separate stereo stream can be used alongside the Ambisonics in a
head-tracked virtual reality experience to provide so-called non-
diegetic audio -- that is, audio that should remain unchanged by
rotation of the listener's head, such as narration or stereo music.
Ogg is a general-purpose container, supporting audio, video, and
other media. It can be used to encapsulate audio streams coded using
the Opus codec. See [RFC6716] and [RFC7845] for technical details on
the Opus codec and its encapsulation in the Ogg container,
respectively.
This document extends the Ogg Opus format by defining two new channel
mapping families for encoding Ambisonics. The Ogg Opus format is
extended indirectly by adding items with values 2 and 3 to the "Opus
Channel Mapping Families" IANA registry. When 2 or 3 are used as the
Channel Mapping Family Number in an Ogg stream, the semantic meaning
of the channels in the multichannel Opus stream is one of the
Ambisonics layouts defined in this document. This mapping can also
be used in other contexts that make use of the channel mappings
defined by the "Opus Channel Mapping Families" registry.
Skoglund & Graczyk Standards Track [Page 2]
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