Information technology — User interface component accessibility — Part 23: Visual presentation of audio information (including captions and subtitles)

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/subtitles. This document acknowledges the various needs and preferences of viewers (end users) as well as the different approaches to visual presentation of audio information. It applies to all presentations of visual alternatives to audio information intended to be presented as captions/subtitles. This document does not apply to the presentation devices or transmission mechanisms used to deliver the content or visual presentations of audio information. These devices could include, but are not limited to: televisions, computers, wireless devices, projection equipment, DVD and home cinema equipment, video game consoles, and other forms of user interfaces technology. This document does not apply to transcoding files and formats for the various video outputs. This document gives guidance on visual presentations which are delivered in the same language as in the audio (i.e., intra-lingual captions/subtitles) and visual presentations which are translated into a different language (i.e., inter-lingual captions/subtitles). This document does not apply to the specific process of language translation. This document helps to improve accessibility. This document does not establish requirements on specific industries (e.g. television broadcasting, motion pictures) nor is it intended to supersede specific international standards within their domain.

Technologies de l'information — Accessibilité du composant interface utilisateur — Partie 23: Présentation visuelle d’informations sonores

General Information

Status
Published
Publication Date
24-Sep-2018
Current Stage
9093 - International Standard confirmed
Start Date
25-Jan-2021
Completion Date
25-Jan-2021
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ISO/IEC 20071-23:2018 - Information technology -- User interface component accessibility
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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)
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

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
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CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
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Published in Switzerland
ii © ISO/IEC 2018 – All rights reserved
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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

© ISO/IEC 2018 – All rights reserved v
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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.
vi © ISO/IEC 2018 – All rights reserved
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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).
© ISO/IEC 2018 – All rights reserved vii
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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
...

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