ISO/IEC 20071-23:2018

INTERNATIONAL ISO/IEC
STANDARD 20071-23
First edition
2018-09
Information technology — User
interface component accessibility —
Part 23:
Visual presentation of audio
information (including captions and
subtitles)
Technologies de l'information — Accessibilité du composant interface
utilisateur —
Partie 23: Présentation visuelle d’informations sonores
Reference number
ISO/IEC 20071-23:2018(E)
©
ISO/IEC 2018

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ISO/IEC 20071-23:2018(E)

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© 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 20071-23:2018(E)

Contents Page
Foreword .vi
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Framework for the visual presentation of audio information . 3
4.1 Purpose . 3
4.2 Motivation . 4
4.3 Locations of presentations . 4
4.4 Modes of presentations . 4
4.5 Modes of access . 5
4.6 Modes of display . 5
4.7 Levels of importance . 5
4.7.1 General. 5
4.7.2 Essential information. 5
4.7.3 Significant information . . 6
4.7.4 Helpful information . 6
4.7.5 Unhelpful information . 6
5 Applicability of requirements and recommendations . 6
5.1 Predictable audio contents . 6
5.2 Unpredictable audio contents . 6
6 Production of visual presentations of audio information . 7
6.1 Consideration to match the intended meaning . 7
6.2 Ease of understanding of visual presentations of audio information . 7
6.3 Consideration of output devices . 7
6.4 Verification of visual presentations of audio information with the intended output
devices . 7
6.5 Connecting visual presentations of audio information data with content data . 7
6.6 Combining multiple visual presentations of audio information . 8
6.7 Update of visual presentations of audio information data . 8
6.8 Evaluation . 8
6.9 Evaluations including contribution of typical users . 8
7 Visual design . 8
7.1 General . 8
7.2 Personalization . 8
7.3 Engagement . 8
7.4 Synchronization of presentations . 9
7.5 Avoidance of information obstruction . 9
7.6 Font size . 9
7.7 Font type .10
7.8 Font face .10
7.9 Upper, lower, and mixed case letters .10
7.10 Contrast and use of colour .10
7.11 Speed .11
7.12 Number of lines .11
7.13 Spacing between characters and lines (kerning and leading) .11
7.14 Correct punctuation.11
7.15 Spacing between words and phrases .12
7.16 Transitions between presentations .12
7.17 Sentence segmentation .12
7.18 Indication of sentence breaks over multiple visual presentations .12
7.19 Additional duration for location change .13
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ISO/IEC 20071-23:2018(E)

7.20 Modes of display .13
8 Visual alternative container (VAC) .13
8.1 General .13
8.2 VAC position and area .13
9 Describing speech .13
9.1 Describing verbal content .13
9.2 Grammar .14
9.3 Vulgar verbal content and slang .14
9.4 Language variation .14
9.5 Foreign accents .14
9.6 Indiscernible audio content .14
9.7 Spelling .14
9.8 Abbreviations .15
9.9 Homophones, homonyms, homographs, heteronyms, and heterographs .15
9.10 Long speech .15
9.11 Describing multiple simultaneous information .15
9.12 Confirmation by content producers when producing visual presentations of speech .15
9.13 Sources of information .15
10 Non-speech information (NSI) .16
10.1 General .16
10.2 Describing NSI .16
10.3 Correct description of NSI .16
10.4 Well-known sound descriptions .16
10.5 Onomatopoeia .16
10.6 Sound effects in speech .16
10.7 Censored language .17
10.8 Paralinguistic sound effects .17
10.9 Discrete and sustained sound effects .17
10.10 Confirmation by content producers when producing visual presentations of NSI .17
10.11 Sources of information .17
11 Music .18
11.1 General .18
11.2 Describing presence of music .18
11.3 Describing the reason or purpose for the music .18
11.4 Provide information that identifies the music .18
11.5 Clarification of music descriptions .19
11.6 Presentation of lyrics .19
11.7 Distinction of lyrics from speech .19
11.8 Confirmation by content producers when producing visual presentations of music .20
11.9 Sources of lyrics .20
12 Emotions .20
12.1 General .20
12.2 Describing intended emotional nuance .20
12.3 Describing the reason or purpose for the emotional nuance .20
12.4 Confirmation by content producers when producing visual presentations of audio
information of emotions .21
13 Silence .21
13.1 General .21
13.2 Describing intentional silence .21
13.3 Describing prolonged silence .21
13.4 Describing the reason or purpose for the silence .21
14 Identifying speakers .21
14.1 General .21
14.2 Means of identifying speakers .22
14.3 Identifying speakers by word .22
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ISO/IEC 20071-23:2018(E)

14.4 Identifying speakers by pictogram .22
14.5 Identifying speakers by colour .22
14.6 Identifying speakers by position .22
14.7 Identifying change of speakers by changing position .22
14.8 Multiple visual presentations of audio information .23
15 Evaluating quality of visual presentations of audio information .23
15.1 General .23
15.2 Quality review process .23
Annex A (informative) Evaluation index and references of guidelines and reports for
accessibility .24
Bibliography .26
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ISO/IEC 20071-23:2018(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 document 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 and IEC 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 JTC 1, Information technology,
Subcommittee SC 35, User interfaces.
A list of all parts in the ISO/IEC 20071 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
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ISO/IEC 20071-23:2018(E)

Introduction
Captions and/or subtitles for audio content provide visual alternatives for audio information in
audiovisual content. This document provides requirements and recommendations on the production
and design of the visual presentation of audio information (including captions and subtitles) that
supports users who cannot make use of the audio content.
The use of this document helps to support universal and inclusive media content production practices.
It provides guidance for producers, exhibitors, or distributors of audio content (including the medium of
distribution and the medium of delivery) to support the accessibility and usability of visual alternatives
of audio content.
Different jurisdictions have different expectations of what belongs in a caption or a subtitle. From the
point of view of the user, what is important is receiving the information in an accessible design, not
the technological means of its delivery. This information can include text conveying speech, sound
information, verbatim transcription of the spoken word content, translations of the spoken word
content, etc. This document uses “visual presentations of audio information” to include all audio
information needed to be made accessible for some users.
Standardized guidance for producing visual presentations of audio information is important to meet a
variety of needs. For example, it is important to recognize acceptable values for specifying typography
variables such as the letter size and/or number of characters in visual alternatives that rely on text.
Providing visual presentations of audio information (including captions and subtitles) can be
beneficial to all, and in particular to diverse users who cannot hear or understand the audio content
in diverse contexts, including: persons with hearing loss, persons who are deaf or hard of hearing,
persons with learning difficulties or cognitive disabilities, persons watching a movie in a non-native
language, persons who need the content to be in another language, persons who cannot hear the audio
content due to environmental conditions, or circumstances where the sound is not accessible (e.g.
noisy surroundings), the sound is not available (e.g. muted, no working speakers), or the sound is not
appropriate (e.g. a quiet library). Although this guidance acknowledges the need of visual presentations
of audio information to provide non-visual presentations for diverse users, it does not include guidance
for producing non-visual presentations, such as spoken captions/subtitles (see ISO/IEC TS 20071-25 for
further reference) and tactile displays (e.g. Braille). The production, delivery, and exhibition of visual
presentations of audio information based on this standard are not intended to interfere with or change
the meaning of the audio content.
The production, delivery and exhibition of visual presentations of audio information vary according to
the time and methodology of production, the technology used for its production, the system of delivery,
and the display (including the brand and model of the display).
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INTERNATIONAL STANDARD ISO/IEC 20071-23:2018(E)
Information technology — User interface component
accessibility —
Part 23:
Visual presentation of audio information (including
captions and subtitles)
1 Scope
This document provides guidance for producers, exhibitors, and distributors on the visual presentation
of alternatives to audio information in audiovisual content, such as captions/subtitles.
This document provides requirements and recommendations that are intended to support users who
are not able to use the audio information, prefer to use a visual representation of audio information, or
prefer both audio and visual presentations.
NOTE Many users do not have a choice, for instance, when in a noisy environment (e.g. bar, restaurant, etc.).
In these situations, the user does not select a visual presentation of audio information but is offered the content
with captions/subtitle
...