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International cooperation
International standards development

International standards development

Edited by Axel Leblois, Executive Director, G3ict 

International Standards Development Organizations (SDOs) play an important role in promoting e-Accessibility for ICT product and services. Policy makers can in most cases rely on their local standards organizations which belong to international SDOs for access to their e-Accessibility programs and standards. Examples include the International Organization for Standardization (ISO), the International Telecommunication Union (ITU), World Wide Web Consortium (W3C) or the World Broadcaster Union (WBU) whose members include many country level organizations. Country-level members are generally listed in the “members” section on the home page of those organizations (with the exception of W3C).   

Policy makers may request from their respective national or regional SDOs recommendations in the context of the development of national or regional programs and policies to ensure consistency with international standards, an example of which is provided below with Mandate 376 of the European Commission to European Standard Organizations. 

e-Accessibility standards are recent. They appeared first in those countries with a high installed base of ICT devices and services and legislation to protect the rights of disabled persons with disabilities and/or with an aging population. There have been two categories of accessibility standards: those which are a component of a technical standard and those which are specifically dedicated to a specific aspect of e-Accessibility. Some were developed at national level, others within international standards development organizations. 

ISO/IEC JTC 1 Special Working Group on Accessibility (SWG-A)
The variety and complexity of e-Accessibility standards led the JTC1 to form a special working group on accessibility in December 2004. See JTC1 Berlin Resolution 24, Establishment of a Special Working Group (SWG) on Accessibility, and Call for Participation.

Its objectives are to:
• Gather user needs
• Inventory all known accessibility standards efforts.
• Identify where voluntary standards efforts are not addressed.
• Track laws, policies, and guidelines.
• Encourage the use of globally relevant voluntary standards.

Its deliverables (some still work in progress) can be downloaded at:

User Needs Mapping (zipped archive)

Standards Inventory (PDF)

Guidance on User Needs Mapping (zipped archive)

The User Needs Summary is a document that gathers accessibility needs of ICT users, including those with the widest range of capabilities. It can be used to analyze whether or not an ICT accessibility standard fully takes into account the needs of persons with disabilities.

The Standards Inventory is a listing of technical standards and guidelines impacting ICT accessibility. It is organized along the following categories of standards:
• High level
• Hardware/equipment oriented
• Software/services oriented
• User capabilities oriented
• Environment oriented
• Communications services oriented
• Other relevant standards

The Guidance on User Needs Mapping is designed to understand the range of user needs, which accessibility aspects are covered by existing standards and to identify where additional guidance might be added to standards to deal with further user needs.

Those documents constitute the first comprehensive analysis of e-Accessibility standards and framework for future standardization based on a systematic analysis of disabled persons specific needs. It is a most welcome initiative for all policy makers and e-Accessibility stakeholders around the world.

All discussions and contributions of participants are publicly available on the SWG-A website at

For an overview of current ICT accessibility standards and work in progress at International Standards Development Organizations in relation to the e-Accessibility agenda of the Convention, check the proceedings of the 2008 ITU-G3ict Global Forum on: “The Convention on the Rights of Persons with Disabilities: Challenges and Opportunities for ICT Standards".

International Standards Development Organizations involved in e-Accessibility
This section contains summaries and links on International SDOs actively involved in e-Accessibility with references to U.S., European and Japanese e-Accessibility standard activities.

InterNational Committee for Information Technology Standards
INCITS Secretariat c/o Information Technology Industry Council,
1250 Eye Street NW, Suite 200,
Washington, DC 20005, USA.
Tel: +1 202 737 8888; Fax: +1 202 638 4922
Email:; Website:

Committees and Working Groups:
V2 - Information Technology Access Interfaces
V2 is the U.S. TAG to ISO/IEC JTC1/SC 35 on "User Interfaces" with its WG6, WG7 and WG8. As such, it provides recommendations on U.S. positions to the JTC 1 TAG.

International Organisation for Standardisation (ISO).
1, Ch. de la Voie-Creuse, Case postale 56, CH-1211 Geneva 20, Switzerland.
Tel: +41 22 749 0111; Fax: +41 22 733 3430

Committees and Working Groups:
ISO/IEC JTC1/SC 35/WG 2 - User Interface Interaction
ISO/IEC JTC1/SC 35/WG 6 - User Interfaces for Disabled and Elderly People
ISO/TC 159/SC 4/WG 5 - Software Ergonomics and Human-Computer Dialogues

International Telecommunication Union (ITU)
The ITU accessibility web site provides references to its work in the field or Radio Communications (ITU-R), Standardization (ITU-T) Development (ITU-D) and in the context of the Internet Governance Forum with the Dynamic Coalition for Accessibility and Disability.

ITU study groups and divisions covering e-Accessibility:
The Joint Coordination Activity on Accessibility and Human Factors JCA-AHF coordinates ICT accessibility activities and act as a single point of contact within ITU and with other institutions including United Nations agencies and Disabled Persons Organizations.

The Standardization Sector of the International Telecommunication Union - (ITU-T) has been seeking to become accessible within itself in line with the United Nations Convention on the Rights of Persons with Disabilities. At the same time, the efforts of the Union aim at encouraging participation by persons with disabilities in the standardization work of ITU.

ITU-T has seen the work on accessibility increase over recent years. It should be noted that the ITU-T has been promoting accessibility with the concept of Total Communication and the principle of “Design for all” since 2000 – with its Recommendation ITU-T F.703. These two elements promoted the concept of Universal Design enshrined in the Convention, eight years before its adoption by the UN. Since then, many other standards – which are called “Recommendations” in ITU parlance – have been written for accessibility and for mainstreaming accessibility within telecommunication/ICT systems. In 2008, the World Standardization Telecommunication Assembly (WTSA 08) built on the momentum for mainstreaming accessibility and addressed for the first time in a Resolution the need for advancement on standards for accessibility and on the need to include persons with disabilities in the standards making process. WTSA-08 Resolution 70 will also assist ITU-T in the task of complying to the provisions of Article 9 of the United Nations Convention on the Rights of Persons with Disabilities.

Though the ITU-T Joint Coordination Activity on Accessibility and Human Factors (JCA-AHF) was created before Resolution 70’s approval, it was designated in the latter to officially assist in this task by helping to increase awareness on accessibility and human factors. It was given the mandate to assist ITU-T Study Groups on how to provide accessibility for persons with disabilities in its standards. It also was mandated to communicate, coordinate and assist not only ITU-T but also the other two ITU Sectors, ITU-D and ITU-R. The JCA-AHF invites recognized outside groups and non members with experience in accessibility and human factors to share best practices by joining the JCA-AHF. Details on how to participate can be found easily on the ITU-T website under the link on accessibility

The technical work on accessibility is covered within various technical committees (called study groups in ITU’s parlance), in coordination with the JCA-AHF.

In ITU-T, the work on accessibility is being encouraged by the use of the Telecommunications Accessibility Checklist, which enables standards writers – who are manufacturers, network providers, operating agencies, regulators, along with member states – to include accessibility and universal design principles  during the early stages of the standards development process, instead of having to do – often expensive – retrofits into existing systems and services.

There are two specific Study Groups that have specific Accessibility and Human Factors responsibilities.

ITU-T Study Group 2 (Operational aspects of service provision and telecommunications management) is the parent study group of the JCA-AHF. Study Group 2 has a specific Human Factors group, namely Question 4/2, Human factors related issues for improvement of the quality of life through international telecommunications. Q4/2 covers more than just the needs of persons with disabilities:  usability for all covers the needs of children, the elderly and persons who may or may not have a disability. For example, one of the most famous Recommendations produced by SG2 human factors is the one that puts a raised dot or indicator on the number 5 on keypads that allows blind persons to navigate the key pad of any telephone. More details can be found on its website at

ITU-T Study Group 16 (Multimedia coding, systems and applications) is the lead study group on telecommunication/ICT accessibility for persons with disabilities. Question 26/16 is the group specifically designated to deal with Accessibility to Multimedia Systems and Services for persons with disabilities. Q26/16 is responsible for developing (or assisting in the development of) multimedia technical standards addressing accessibility needs of persons with disabilities. It also reviews accessibility features included in telecom standards developed in other Study groups. Examples cover interoperability for text telephone terminals, real-time text in fixed and mobile networks, and accessibility in Next Generation Networks (NGN) and Internet Protocol Television (IPTV). New work will address networked cars and home networking scenarios, and the development of standards for relay services for deaf and speech-impaired persons.

Question 26/16 is where the ITU-T Telecommunications Accessibility Checklist was created along with Recommendation ITU-T F.790, which gives guidance on understanding the topic of accessibility and the ways that accessibility may be incorporated in ICT products and services for older persons and persons with disabilities.

More details can be found at the ITU-T website at

All of the documents mentioned above and listed below can be downloaded without charge from the ITU-T website.

ITU-T Recommendations on and including accessibility and human factors
Here are some examples of the standards developed by ITU–T that address accessibility and usability needs of persons with disabilities, older persons, and children. All ITU-T Recommendations can be downloaded for free from the ITU-T website at

The following ITU-T Recommendations on accessibility are a result of SG 2’s work:

•    E.121: “Pictograms, symbols and icons to assist users of the telephone service” (Easy-to-understand symbols)

•    E.135: “Human factor aspects of public telecommunication terminals for people with disabilities”

•    E.136: “Specification of a tactile identifier for use with telecommunication cards”

•    E.138: “Human factor aspects of public telephones to improve their usability for older people”.

The following ITU-T Recommendations on accessibility are a result of SG 16’s work:
•    V.18   Provides for harmonization of text telephony
•    V.151 Procedures for the end-to-end connection of analogue PSTN text telephones over an IP network utilizing text relay
•    T.140 specifies the general presentation protocol for text conversation
•    T.134 details how to use text conversation in the T.120 data conferencing environment
•    H.323 Annex G defines text conversation in H.323’s packet multimedia environment
•    H.248.2 allows gateway procedures between Text Telephony in PSTN and real-time text in IP and other networks
•    H Series Supplement 1 gives users the requirements on video communication for sign language and lip reading
•    Telecommunication Accessibility Checklist for standards writers:.
•    F.790 provides telecommunications accessibility guidelines for older persons and persons with disabilities

ITU-T SG 16 Recommendations in which sections on accessibility have been integrated:
•    Definition in F.703 of Total Conversation and Text Telephony services, offering real-time text, video and audio communication
•    Definition of the real-time conversational text medium in F.700
•    Inclusion in H.320 of real-time text conversation in ISDN multimedia
•    Section on transport of real-time text in ISDN multimedia environments in H.224
•    Sections on modem negotiation for text telephony in V.8
•    Sections in V.8 bis on modem negotiation for text telephony
•    Sections in V.250 on control of V.18 modems
•    Inclusion in H.324 of real-time text conversation in circuit switched multimedia
•    Section in H.245 for handling real-time text connections in H.324 and H.323 multimedia environments
•    Inclusion in T.120 of real-time text in data conferencing
•    Section in T.124 for handling real-time text sessions in the T.120 environment
•    Section in G.168 for testing of echo cancellation in calls with text telephony
•    Section in F.724 for accessible media additions in service description and requirements for video telephony services over IP networks
•    Section in F.733 for accessible media additions in multimedia conference
services over IP
•    Section in F.741 for accessible media additions in service description and requirements for audiovisual on-demand services
•    Section in F.742 for accessible media additions in service description and requirements for distance-learning services
•    Inclusion in V.152 of text telephony considerations in voice band data gateway procedures
•    Accessibility provisions in Y.2000 – Series Supplement 1 NGN Release 1 scope - the accessibility guidelines are referred to in the specifications for NGN Release 1.

Most recently, some other ITU-T study groups’ standards work on accessibility has been achieved:
•    ITU-T Recommendation Y.1901 “Requirements for the support of IPTV services”. The text produced by ITU-T Study Group 13 includes some key terms and definitions on accessibility, such as “Accessibility feature,” “Universal design” and “Captions”. Accessibility features are included in the main architecture for IPTV services and describe functionality expected from IPTV terminal devices. One example is the electronic programme guides where the associated metadata to be provided to users must include elements that facilitate access and usability by the widest possible range of users albeit particularly relevant for the end user in terms of accessibility and persons with disabilities, these are not just accessibility features but mainstream features useful to all.

More examples of architecture recommendation read as follows:
-    “the IPTV architecture is required to support the end-user with the ability to choose a preferred language option (audio, subtitles, captioning, supplementary video and supplementary descriptive audio) from various languages that the content provider pre-defined and the service provider delivered.”;
-    “The IPTV architecture is required to support the availability of accessibility features (captions, subtitles, descriptive audio and multiple video streams such as for sign-language) and their synchronization with the main content when viewing in normal playback.”
One of the unique features in this Recommendation is that it not only has a public service section but also a special Appendix indicating the location of the mainstreamed accessibility features within Recommendation itself. This makes it easier for implementers and policy makers to locate and verify whether accessibility features are indeed implemented, e.g. if required by regulation or other bodies.

Ongoing and future work on standardization and accessibility
Draft recommendation “Y.NGN-vehicle “Framework of Networked Vehicle in NGN” is an example of new work that will include accessibility in its development. This draft recommendation describes the framework of networked vehicle in the context of NGN. It identifies the relationship between NGN and networked vehicles, taking into consideration the necessity to support vehicle oriented communication. The final text would hopefully contain accessibility requirements.

ITU-T and the Internet Governance Forum
ITU-T is also active within the Internet Governance Forum (IGF), where it initiated and continues to help sponsor along with its partners, the Dynamic Coalition on Accessibility and Disability (DCAD). ITU-T provides the DCAD website, secretariat support and a coordinator. DCAD’s goal is to facilitate communication from persons with disabilities, NGOs and civil society so that their voices are included in the key debates around Internet governance. Indeed, many have participated by giving presentations in the past IGF meetings as well giving guidance to the IGF secretariat to help make IGF meetings and respective websites more accessible to persons with disabilities. This ensures that information about appropriate communications technologies, that tools that facilitate accessibility are provided and that the needs of persons with disabilities are included in the activities of IGF. DCAD produced the first IGF deliverable, the Accessibility Declaration at its meeting in Hyderabad, India, December 2008. Its steering committee and members continue to work together throughout the year by captioned web-conference calls so that all, including deaf persons, can participate.

ITU-T, captioned meetings and sign language interpretation
The ITU-T began including sign language in its workshops as early as 2003 at the World Telecom Forum during its first Accessibility workshop. Sign language for deaf participants can be provided upon request.

ITU-T started captioning workshops beginning in 2007. It now captions many meetings and most conference calls dealing with accessibility or upon request, in line with the UN Convention. After WTSA Resolution 70, ITU-T commissioned the development of a study on how to make more of its activities accessible. It is still an ongoing process, not complete and but is continuing grow and increasing allowing persons with disabilities to more fully participate in discussions.

Participation of non-members

Currently, non-members can be invited on an exceptional basis by the chair to attend a meeting in ITU. In the particular area of accessibility and human factors, contribution from end-users is fundamental, however most commonly they are not members. Therefore, representatives of end-user organizations capable of providing expert advice to ITU’s standardization work are commonly invited to attend relevant technical meetings, such as those of Q4/2 and Q26/16. Additionally, they can be represented in the JCA-AHF and in the DCAD and contribute their expertise. That can make a difference in making new technologies, as they emerge, accessible to many more people than in the past.

The ITU-D Study Group 1 covers "Access to telecommunication services for people with disabilities" Reference: ITU-D SG 1 Question 20/1

Two emerging technology groups also include important considerations for e-Accessibility:

Focus Group on IPTV.

Joint Coordination Activity on RFID.

Other activities of ITU related to ICT accessibility:

BDT/Special Initiatives.

ITU-R Sector contribution to Bridging the Digital Disabilities Divide.

Recent ITU publications and recommendations relative to e-Accessibility:

Recommendation ITU-R M.1076 - Wireless communication systems for persons with impaired hearing.

Recommendation F 790 on Telecommunications accessibility guidelines for older persons and persons with disabilities.

Telecommunications Accessibility Checklist

World Wide Web Consortium Web Accessibility Initiative (W3C-WAI): W3C-WAI’s objective is to lead the Web to its full potential by promoting a high degree of usability for people with disabilities. The Web Accessibility Initiative develops its work through W3C's consensus-based process, involving different stakeholders in Web accessibility. These include industry, disability organizations, government, accessibility research organizations, and more.
W3C WAI, in partnership with organizations around the world, pursues accessibility of the Web through five primary activities:
•    ensuring that core technologies of the Web support accessibility
•    developing guidelines for Web content, user agents, and authoring tools
•    facilitating development of evaluation and repair tools for accessibility
•    conducting education and outreach
•    coordinating with research and development that can affect future accessibility of the Web

WCAG 2.0 is the latest Web Content Accessibility Guidelines (WCAG) of the W3C Web Accessibility Initiative.

The Web Content Accessibility Guidelines (WCAG) documents explain how to make Web content accessible to people with disabilities. Web "content" generally refers to the information in a Web page or Web application, including text, images, forms, sounds, and such.
WCAG is part of a series of accessibility guidelines, including the Authoring Tool Accessibility Guidelines (ATAG) and the User Agent Accessibility Guidelines (UAAG). Essential Components of Web Accessibility explains the relationship between the different guidelines.
DAISY Consortium was formed in May 1996 by talking book libraries to lead the worldwide transition from analog to Digital Talking Books. DAISY denotes the Digital Accessible Information System. Members of the Consortium actively promote the DAISY Standard for Digital Talking Books because it promises to revolutionize the reading experience for people who have reading disabilities. Specifically, the Consortium's vision is that all published information is available to people with print disabilities, at the same time and at no greater cost, in an accessible, feature-rich, navigable format.   


European Standards Development Organizations involved in e-Accessibility
European Committee for Standardisation (CEN)
European Committee for Electrotechnical Standardisation (CENELEC)
European Telecommunications Standards Institute (ETSI)
ICT Standards Board ICTSB is an initiative from the three recognized European standards organizations to co-ordinate specification activities in the field of Information and Communications Technologies.

Europe Standardization Activities Overview by ICTSB

Main standardization and standards related activities at European level:

ETSI  TCHF – Technical Committee on Human Factors is the committee responsible for standards and guidelines dealing with ease of use and accessibility of telecommunication equipment and services, including the requirements of older and disabled people. 

The CEN/ISSS Workshop on Design-for-All and Assistive Technologies for ICT was the focal point in CEN/ISSS between 2001 and 2003 for the inclusion of eAccessibility and Design-for-All considerations in its ICT standardization work.  eAccessibility work at CEN has further taken place in a number of other Workshops such as WS/WAC, WS/DPA, WS/eURI.  

CEN/TC 224/WG 16 is responsible for Human Interface issues in relation to smart cards and terminals: CEN/TC 224/WG16 Work Items.

In the ICT area, a standards coordination group has been created, called DATSCG, the Design-for-all and Assistive Technology Standardization Co-ordination Group.

ANEC  is the European Association for the co-ordination of consumer representation in standardization. The association was established in 1995 to give the opportunity to consumers to be heard in the process of technical standardization. ANEC represents consumers from all European Union and European Free Trade Area countries. ICT accessibility activities in ANEC are taking place in the ANEC ICT Working Group and ANEC Design for All Working Group. 

ANEC participates principally through its voluntary experts in the standards development work of the three European Standards Organizations (ESOs) recognized by the European Union and EFTA: CEN, CENELEC, ETSI and their joint initiative ICTSB. It also participates in other organizations which develop standards whose use could directly or indirectly affect the European consumer. One such organization is the World Wide Web Consortium (, responsible for developing the protocols and guidelines necessary to support the Web.

ANEC delivered a report on “Consumer Requirements in Standardization relating to the Information Society": January 2005 (PDF).
Development of a Public Procurement policy at EC level:

Standardization Mandate 376 to the European Standards Organizations in support of European Accessibility Requirements for Public Procurement of Products and Services in the ICT domain.

United States Standards Development Organizations involved in e-Accessibility
American National Standards Institute

1819 L Street NW, 6th Floor,
Washington DC 20036, USA.
Tel: +1 212 642 4900; Fax: +1 202 293 9287
Email:; Website:

Committees and Working Groups:
INCITS V2 – Information Technology Access Interfaces
V2 is the U.S. TAG to ISO/IEC JTC1 SC35 on “User Interfaces” and its WG6, WG7 and WG8. As such, it provides recommendations on U.S. positions to the JTC 1 TAG.

Bluetooth Special Interest Group
500 108th Avenue NE, Suite 250, Bellevue, WA 98004, USA.
Tel: +1 425 691 3535
Specification of the Bluetooth System: Volume 1 – Core (Revision 1.1) (2001)
Specification of the Bluetooth System: Volume 2 – Profiles (Revision 1.1) (2001)

IEEE Institute of Electrical and Electronics Engineers
3 Park Avenue, 17th Floor,
New York, New York 10016-5997, USA.
Tel: +1 212 419 7900; Fax: +1 212 752 4929
IEEE 1621 (2004) Standard for user interface elements in power control of electronic devices employed in office/consumer environments

Telecommunications Industry Association

The Telecommunications Industry Association (TIA) is the leading trade association representing the global information and communications technology (ICT) industries through standards development, government affairs, business opportunities, market intelligence, certification and world-wide environmental regulatory compliance. With support from its 600 members, TIA enhances the business environment for companies involved in telecommunications, broadband, mobile wireless, information technology, networks, cable, satellite, unified communications, emergency communications and the greening of technology. TIA is accredited by ANSI. 

Its standardization work focuses on interference of digital cordless phones experienced by users with hearing aids and TTY communications across the Internet Protocol (IP) portion of the public switched telephone network. It also serves as an organizational member of the American National Standards Institute (ANSI) Accredited Standards Committee (ASC) 63 which develops standards related to electromagnetic compatibility. This Committee developed and published C63.19, a standard that specifies hearing aid compatibility requirements for cell phones.

Japan Standards Development Organizations involved in e-Accessibility
Japan e-Accessibility initiatives date back to 1995 when an "Accessibility Guideline for Use of Computers by People with Disabilities" was published by MITI in 1995. In 2000 it was substituted by a revised MITI report entitled "Accessibility Guidelines for Use of Computers by People with Disabilities and the Elderly." An accessibility guideline for the use of telecommunication facilities by people with disabilities was announced by the Ministry of Posts and Telecommunications in 1998, and a guideline for the creation of accessible Internet web contents by persons with disabilities was jointly announced by the Ministry of Posts and Telecommunications and the Ministry of Health and Welfare in 1999.

The Japan Industrial Standards Committee (JISC) formed an Ad-hoc Committee on Standardization for the Elderly and People with Disabilities, which published a report in 1998 emphasizing the importance of e-Accessibility standardization.

The Japan Standards Association Information Technology Research and Standardization Center (INSTAC) established the Standardization Investigation Committee for Realizing Barrier-Free Access to Information in September of 2000. Based on the Committee's conclusions, the Standardization Investigation Committee for Improvement of Accessibility Common to Areas of Information Technology and Software Products was organized in April of 2001 within INSTAC, and started its activities as a body to carry out investigations entrusted by the government.

Today, Japan has a series of ICT accessibility standards in place. The name of the standards is: “Guidelines for Older Persons and Persons with Disabilities: Information Communication Equipment, Software and Services,” of which there are five distinct parts:   
    Part 1 – Common Guidelines; developed in 2004

    Part 2 – Information Processing Equipment; developed in 2004

    Part 3 – Content; developed in 2004

    Part 4 – Telecommunication Equipment; developed in 2005

    Part 5 – Office Equipment; developed in 2006

Japan is an active member of the ISO/IEC JTC 1 Special Working Group on Accessibility (SWG-A).

Useful resources to search for e-Accessibility Standards
ISO/IEC JTC 1 Information Technology SWG-A web site at

Center for Excellence in Universal Design of the National Disability Authority of Ireland: list of essential e-Accessibility Guidelines and Standards. standards database by subject A very well organized database to locate standards by type of technology. Tiresias is a division of the RNIB in the UK.

For an overview of current ICT accessibility standards and work in progress at International Standards Development Organizations in relation to the e-Accessibility agenda of the Convention, check the proceedings of the 2008 ITU-G3ict Global Forum on: “The Convention on the Rights of Persons with Disabilities: Challenges and Opportunities for ICT Standards".

"Accessibility feature: An additional content component that is intended to assist people hindered in their ability to perceive an aspect of the main content. Examples: captions for the hard of hearing, subtitles in various languages, sign-language interpretation video and descriptive audio” (para 3.2, page 8 of the text).

"Universal design: It is the design of the products and environments to be useable by all people, to the greatest extent possible by including accessibility features in the original design to prevent the need for adaptation after deployment. 

Note: The intent of universal design is to simplify life for everyone by making products, communications, and the built environment more usable by as many people as possible at little or no extra cost. Universal design benefits people of all ages and abilities.”

"Captions: Captions provide a real-time on-screen transcript of the dialogue as well as any sound effects.
Note: This service can be provided by means of either textual or graphical supplementary content. The captions and the dialogue are usually in the same language. The service is primarily to assist users having difficulty hearing the sound. Ideally, users may have some control over the position and size of the presentation. Different speakers are distinguished, usually by different colours.”