ISO/IEC 23091-3:2018

INTERNATIONAL ISO/IEC
STANDARD 23091-3
First edition
2018-04
Information technology — Coding-
independent code points —
Part 3:
Audio
Technologies de l'information — Points de code indépendants du
codage —
Partie 3: Audio
Reference number
ISO/IEC 23091-3:2018(E)
©
ISO/IEC 2018

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ISO/IEC 23091-3:2018(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
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ISO/IEC 23091-3:2018(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Code points and usage . 2
4.1 General . 2
4.2 Applicability . 3
5 Principles for definition and referencing of code points . 3
5.1 Code point encoding and defaults . 3
5.2 Externally defined values . 3
5.3 Reference format . 3
5.4 Uniform Resource Name format . 4
6 Audio code point definitions . 4
6.1 Loudspeaker index and speaker channel position . 4
6.2 Loudspeaker layout index and channel configuration. 7
6.3 Loudspeaker positioning.12
6.4 Program loudness level .17
6.5 Anchor loudness level .17
6.6 Range of loudness .18
6.7 Top of loudness range .18
6.8 Maximum of momentary loudness level .18
6.9 Maximum of short-term loudness level .18
6.10 Short-term loudness level .18
6.11 Peak level .18
6.12 Compressor characteristic .19
Bibliography .22
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ISO/IEC 23091-3:2018(E)

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical
activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the
work. In the field of information technology, ISO and IEC have established a joint technical committee,
ISO/IEC JTC 1.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/IEC JTC1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
1)
Together with ISO/IEC 23091-1 and ISO/IEC 23091-2 , this first edition of ISO/IEC 23091-3 cancels and
replaces ISO/IEC 23001-8:2016, which has been technically revised.
A list of all parts in the ISO/IEC 23091 series can be found on the ISO website.
1) Under preparation. Stage at time of publication: ISO/IEC DIS 23091-2:2017.
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ISO/IEC 23091-3:2018(E)

Introduction
There is a need to identify some characteristics of media that are logically independent of the
compression format (for example, aspects that relate to the sourcing or presentation or the role of the
media component). These media characteristics have typically been documented by fields that take an
encoded value or item selected from an enumerated list, herein called code points.
Prior to the existence of the parts of this standard, the specification of these fields was copied into
every document that needed them, sometimes with new values being added.
This past practice has raised a number of issues, including the following.
a) A lack of a formal way to avoid conflicting assignments being made.
b) Having additional values defined in later documents that may be practically used with older
compression formats, without clear formal applicability of these new values.
c) Any update or correction of code point semantics can incur significant effort to update all places in
which the code point is specified, instead of enabling a single central specification to apply.
d) The choice of reference for other specifications (such as container or delivery formats) not being
obvious; wherein a formal reference to a compression format specification appears to favour that
one format over others, and also appears to preclude definitions defined in other compression
format specifications.
e) Burdensome maintenance needs to ensure that a reference to material defined in a compression
format specification is maintained appropriately over different revisions of the referenced format
specification, as the content of a compression format specification may change over time and is
ordinarily not intended as a point of reference for defining such code points.
The parts of this series provide a central definition of such code points to address these issues. In
this document, code points that are used for audio are specified. ISO/IEC 23091-1 specifies a Uniform
Resource Name (URN) format that can be used with the code points defined in all parts of the series,
including this one.
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INTERNATIONAL STANDARD ISO/IEC 23091-3:2018(E)
Information technology — Coding-independent code
points —
Part 3:
Audio
1 Scope
This document defines various code points and fields that establish properties of an audio stream
that are independent of the compression encoding and bit rate. These properties could describe the
appropriate interpretation of decoded audio data or could, similarly, describe the characteristics of
such signals before the signal is compressed by an encoder that is suitable for compressing such an
input signal.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO/IEC 23091-1, Information technology — Coding independent code points — Part 1: Systems
Rec. ITU-R BS.1771-1, Requirements for loudness and true-peak indicating meters
EBU R 128, Loudness normalization and permitted maximum level of audio signals
EBU Tech 3341, Loudness Metering: ‘EBU mode’ metering to supplement Loudness normalization in
accordance with EBU R 128
EBU Tech 3342, Loudness Range: A measure to supplement Loudness normalisation in accordance with
EBU R 128
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1
channel
Ch
conceptual representation of an audio signal for coding or transmission as it may be used within the
digital signal processing chain of an audio codec
3.2
dynamic range compressor
DRC
process that modifies the amplitude of an audio signal
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ISO/IEC 23091-3:2018(E)

3.3
K-weighted
frequency weighting by means of a two-stage filter
Note 1 to entry: As defined in Reference [3].
3.4
LKFS
loudness, K-weighted, relative to nominal full scale
Note 1 to entry: As defined in Reference [3].
3.5
loudspeaker
LS
physical loudspeaker with a given geometric position relative to the listener and, if applicable, a
label or name
Note 1 to entry: Even though the loudspeaker names used in this document each describe one discrete
loudspeaker position, some loudspeaker signals may, in practice, be rendered on a loudspeaker array consisting
of multiple loudspeakers which are all driven with the same audio signal, for example, in a theatrical setting.
3.6
loudspeaker index
association of a loudspeaker geometric position to a given index
3.7
loudspeaker layout
set of loudspeakers with a specific constellation of geometric positions meant for authoring or play-
back of audio content
3.8
lousdspeaker layout index
association of a loudspeaker layout to a given index
4 Code points and usage
4.1 General
This Clause identifies the code points defined in this document, as listed in Table 1 with cross-references
to the subclause in which each is specified.
Table 1 — List of code points
Name Abstract Subclause
OutputChannelPosition Audio channel assignment 6.1
ChannelConfiguration Audio channel configuration 6.2
LoudspeakerGeometry Audio loudspeaker geometry 6.3
LoudspeakerElevation Audio loudspeaker elevation 6.3
LoudspeakerAzimuth Audio loudspeaker azimuth 6.3
ProgramLoudness Audio program loudness level 6.4
AnchorLoudness Audio anchor content loudness level 6.5
LoudnessRange Range of loudness 6.6
LoudnessRangeTop Top value of loudness range 6.7
MomentaryLoudnessMax Maximum Loudness (400 ms window) 6.8
ShortTermLoudnessMax Maximum Loudness (3 s window) 6.9
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ISO/IEC 23091-3:2018(E)

Table 1 (continued)
Name Abstract Subclause
ShortTermLoudness Loudness (3 s window) 6.10
SamplePeakLevel Level of sample peak magnitude 6.11
TruePeakLevel Level of true peak 6.11
DrcCharacteristic Index of DRC characteristic 6.12
4.2 Applicability
The usage of this document is illustrated in Figure 1. This document can be used to provide universal
descriptions to assist interpretation of signals following decoding or to describe the properties of the
signals before they are encoded.
This document provides code points for coding-independent description of multimedia signal
characteristics.
Figure 1 — Scope of this document
5 Principles for definition and referencing of code points
5.1 Code point encoding and defaults
The code points defined herein may be specified as a value or a label of an enumerated list. The definition
of their encoding and representation (e.g. as a binary number) is the responsibility of the specification
using the code point, as is the identification of any applicable default value not specified herein. It is also
possible for external specifications to use a mapping to values defined here, if they wish to preserve
identical semantics but different code point assignments.
Guidance is given for each code point as to a suitable type (e.g. unsigned integer) and a suitable value
range (e.g. 0 to 63) for assistance in writing derived specifications. In some instances, default flag
values are provided that are suggested to be inferred for code point parameters with associated flags
that may not be explicitly signalled or specified in derived specifications.
5.2 Externally defined values
If the external specification permits values not defined by this document to be identified in the same
field that carries values defined by this document, then that other specification should identify how
values defined herein can be distinguished from values not defined herein.
5.3 Reference format
References to code points in this document should use only the code point name (i.e. a "Name" from
Table 1) and specification title, and not use subclause numbers or any other "fragile" reference such as a
table number. Example: "ChocolateDensity as defined in ISO/IEC 23091-1".
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ISO/IEC 23091-3:2018(E)

5.4 Uniform Resource Name format
ISO/IEC 23091-1 specifies a URN format that may be used.
6 Audio code point definitions
6.1 Loudspeaker index and speaker channel position
Type: Unsigned integer, enumeration
Range: 0 – 127
OutputChannelPosition indicates the descriptive loudspeaker position in the 3D environment relative
to the listener.
For the purpose of this document, the terms "loudspeaker" and "loudspeaker layout" are preferred
over the terms "channel" and "channel configuration" because the latter appear to be potentially codec-
dependent. Certain standards use these terms (channel, channel configuration) and in their respective
contexts should be understood synonymously to the terms "loudspeaker" and "loudspeaker layout".
When a speaker is indicated as being at an explicit position, the position is provided by some means
outside the scope of this specification. That might include signalling by azimuth, elevation, distance, or
by some other suitable means.
Table 2 — Definition of loudspeaker index, OutputChannelPosition
Loudspeaker position
Value Loudspeaker position according to Reference [1]
(informative)
Abbr. Name Abbr. Name
0 L Left front FL Front left
1 R Right front FR Front right
2 C Centre front FC Front centre
3 LFE Low frequency enhancement LFE1 Low frequency effects-1
4 Ls Left surround LS Left surround
5 Rs Right surround RS Right surround
6 Lc Left front centre FLc Front left centre
7 Rc Right front centre FRc Front right centre
8 Lsr Rear surround left BL Back left
9 Rsr Rear surround right BR Back right
10 Cs Rear centre BC Back centre
11 Lsd Left surround direct LSd Left surround direct
12 Rsd Right surround direct RSd Right surround direct
13 Lss Left side surround SL Side left
14 Rss Right side surround SR Side right
15 Lw Left wide front FLw Front left wide
16 Rw Right wide front FRw Front right wide
17 Lv Left front vertical height TpFL Top front left
18 Rv Right front vertical height TpFR Top front right
19 Cv Centre front vertical height TpFC Top front centre
20 Lvr Left surround vertical height rear TpBL Top back left
21 Rvr Right surround vertical height rear TpBR Top back right
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Table 2 (continued)
Loudspeaker position
Value Loudspeaker position according to Reference [1]
(informative)
Abbr. Name Abbr. Name
22 Cvr Centre vertical height rear TpBC Top back centre
23 Lvss Left vertical height side surround TpSiL Top side left
24 Rvss Right vertical height side surround TpSiR Top side right
25 Ts Top centre surround TpC Top centre
26 LFE2 Low frequency enhancement 2 LFE2 Low frequency effects-2
27 Lb Left front vertical bottom BtFL Bottom front left
28 Rb Right front vertical bottom BtFR Bottom front right
29 Cb Centre front vertical bottom BtFC Bottom front centre
30 Lvs Left vertical height surround TpLS Top left surround
31 Rvs Right vertical height surround TpRS Top right surround
32 Reserved
33 Reserved
34 Reserved
35 Reserved
36 LFE3 Low frequency enhancement 3
37 Leos Left edge of screen
38 Reos Right edge of screen
39 Hwbcal half-way between centre of screen
and left edge of screen
40 Hwbcar half-way between centre of screen
and right edge of screen
41 Lbs Left back surround
42 Rbs Right back surround
43–125 Reserved Reserved
126 Expl Explicit position (see text)
127 Unknown / undefined
Figure 2 shows a subset of the loudspeaker positions in the 3D environment relative to the listener, with
each loudspeaker labelled with an abbreviation from Table 2. Loudspeakers lying on the innermost box
are in the bottom level, those on the middle box are in the middle level, and those on the oute
...