Ambisonics in an Ogg Opus Container
draft-ietf-codec-ambisonics-09
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Active Internet-Draft (codec WG)
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2018-08-16
(latest revision 2018-08-13)
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draft-graczyk-codec-ambisonics
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Tim Terriberry
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Ben Campbell
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codec J. Skoglund
Internet-Draft Google LLC
Updates: 7845 (if approved) M. Graczyk
Intended status: Standards Track August 13, 2018
Expires: February 14, 2019
Ambisonics in an Ogg Opus Container
draft-ietf-codec-ambisonics-09
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 Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 14, 2019.
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 Expires February 14, 2019 [Page 1]
Internet-Draft Opus Ambisonics August 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 . . . . . . . . . . . . . . . . . . . . . 6
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. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
Ambisonics is a representation format for three dimensional sound
fields which can be used for surround sound and immersive virtual
reality playback. See [gerzon75] 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 - audio which should remain unchanged by listener head
rotation; e.g., 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 IANA
"Opus Channel Mapping Families" 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 which make use of the channel mappings
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