Ambisonics in an Ogg Opus Container
draft-ietf-codec-ambisonics-09

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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

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   This Internet-Draft will expire on February 14, 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
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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