RTC Accessibility User Requirements

W3C Editor's Draft

This version:
https://w3c.github.io/apa/rtc/
Latest published version:
https://www.w3.org/TR/RAUR/
Latest editor's draft:
https://w3c.github.io/apa/rtc/
Editors:
(W3C)
(W3C)

Abstract

This document outlines various accessibility related user needs, requirements and scenarios for Real-time communication (RTC). These user needs should drive accessibility requirements in various related specifications and the overall architecture that enables it. It first introduces a definition of RTC as used throughout the document, and outlines how RTC accessibility can support the needs of people with disabilities. It defines the term user needs as used throughout the document and then goes on to list a range of these user needs and their related requirements. Following that some quality related scenarios are outlined and finally a data table that maps the user needs contained in this document to related use case requirements found in other technical specifications.

This document is most explicitly not a collection of baseline requirements. It is also important to note that some of the requirements may be implemented at a system or platform level, and some may be authoring requirements.

Status of This Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.

This document was published by the Accessible Platform Architectures Working Group as an Editor's Draft.

Comments regarding this document are welcome. Please send them to public-apa@w3.org (archives).

Publication as an Editor's Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

This document was produced by a group operating under the W3C Patent Policy. The group does not expect this document to become a W3C Recommendation. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

This document is governed by the 1 March 2019 W3C Process Document.

1. Introduction

What is Real-time communication (RTC)?

The traditional data exchange model is client to server. Real-time communication (RTC) is game-changing. It is enabled in part, by specifications like WebRTC as this provides real-time peer to peer Audio, Video and Data exchange directly between supported web browsers without the need for browser plugins, as well as fast applications for video/audio calls, text chat, file exchange, screen sharing and gaming. However, WebRTC is not the sole specification with responsibility to enable accessible real-time communications, as use cases and requirements are broad - as outlined in the IETF RFC 7478 'Web Real-Time Communication Use Cases and Requirements' document. [ietf-rtc]

Accessible RTC is enabled by a combination of technologies and specifications such as those from the Media Working Group, Web and Networks IG, Second Screen, and Web Audio Working group as well as AGWG and ARIA. APA hopes this work will inform how these groups meet various responsibilities for enabling RTC, as well updating use cases in various groups. For example, you can view current work on WebRTC Next Version Use Cases First Public Working Draft.[webrtc-use-cases]

1.1 Real-time communication and accessibility

RTC has the potential to allow improved accessibility features that will support a broad range of user needs for people with a wide range of disabilities. These needs can be met through improved audio and video quality, audio routing, captioning, improved live transcription, transfer of alternate formats such as sign-language, text-messaging / chat, real time user support, status polling.

1.2 User needs definition

This document outlines various accessibility related user needs for Accessible RTC. These user needs should drive accessibility requirements for Accessible RTC and its related architecture. These come from people with disabilities who use assistive technology (AT) and wish to see the features described available within Accessible RTC enabled applications.

User needs are presented with related requirements and also some in a range of scenarios; (which can be thought of as similar to User stories). User needs and requirements are being actively reviewing by RQTF/APA in the context of the broader scope and application of the contents of this document.

2. User needs and requirements

The following outlines a range of user needs and requirements. The user needs below have also been compared to existing use cases for Real-Time Text (RTT) such as the IETF Framework for Real-Time Text over IP Using the IETF Session Initiation Protocol RFC 5194 and the European Procurement Standard EN 301 549. [rtt-sip] [EN301-549]

2.1 Incoming calls and caller ID

2.2 Routing and communication channel control

2.3 Dynamic audio description values in live conferencing

2.4 Quality synchronisation and playback

2.5 Simultaneous voice, text & signing

NOTE: This could be partially enabled via RTT in WebRTC.

2.6 Emergency calls: Support for Real-time text (RTT)

2.7 Video relay services and (VRS) and remote interpretation (VRI)

2.8 Distinguishing sent and received text with RTT

2.9 Call participants and status

2.10 Live transcription and captioning support

2.11 Assistance for users with cognitive disabilities

2.12 Personalized symbol sets for users with cognitive disabilities

2.13 Internet relay chat (IRC) style interfaces required by blind users

2.14 Deaf users: Video resolution and frame rates

3. Quality of service scenarios

3.1 Bandwidth for audio

Scenario: A hard of hearing user needs better stereo sound so they can have a quality experience in work calls or meetings with friends or family. Transmission aspects, such as decibel range for audio needs to be of high-quality. Industry allows higher audio resolution, but still mostly audio in mono only.

3.2 Bandwidth for video

Scenario: A hard of hearing user needs better stereo sound so they can have a quality experience in watching HD video or having HD meeting with friends or family. Transmission aspects, such as frames per minute for video quality needs to be of high-quality.

NOTE: EN 301 549 Section 6, recommends for WebRTC enabled conferencing and communication the application shall be able to encode and decode communication with a frequency range with an upper limit of at least 7KHz. More details can be found at Accessible Procurement standard for ICT products and services EN 301 549 (PDF)

NOTE: WebRTC lets applications prioritise bandwidth dedicated to audio / video / data streams; there is also some experimental work in signalling these needs to the network layer as well as support for prioritising frame rate over resolution in case of congestion. [webrtc-priority]

A. Acknowledgments

A.1 Participants of the APA working group active in the development of this document:

A.2 Enabling funders

This work is supported by the EC-funded WAI-Guide Project.

B. References

B.1 Informative references

[EN301-549]
Accessibility requirements suitable for public procurement of ICT products and services in Europe. CEN/CENELEC/ETSI. August 2018. URL: http://mandate376.standards.eu/standard
[ietf-relay]
Interoperability Profile for Relay User EquipmentPI. IETF. August 5, 2019. URL: https://tools.ietf.org/html/draft-rosen-rue-00/
[ietf-rtc]
Web Real-Time Communication Use Cases and Requirements. IETF. March 2015. URL: https://tools.ietf.org/html/rfc7478
[rtt-sip]
Framework for Real-Time Text over IP Using the Session Initiation Protocol (SIP). IETF, Network Working Group. June 2008. URL: https://tools.ietf.org/html/rfc5194
[webrtc-priority]
WebRTC DSCP Control API. W3C. 12 February 2020. URL: https://w3c.github.io/webrtc-priority/
[webrtc-use-cases]
WebRTC Next Version Use Cases. W3C. 11 December 2018. URL: https://www.w3.org/TR/webrtc-nv-use-cases/