UNIVERSAL USABILITY IN PRACTICE

Texual equivalents for audio/video representations of content

Yu-Lin Wen (ylwen@cs.umd.edu)
Department of Computer Science
University of Maryland
College Park, MD 20742 USA
April 2001

Introduction

The Web Content Accessibility Guidelines 1.0 [4] gives the following definition: Content is "equivalent" to other content when both fulfill essentially the same function or purpose upon presentation to the users. Text equivalents must be written so that they convey all essential content. Textual equivalents for audio/video representations of content can be further divided into two categories. One deals with textual equivalents for audio/video content, including audio/video and animations. The other one deals with textual equivalents for images, including images, graphs, and charts. 

So, why are textual equivalents for audio/video (image/animation) representations of content important? The National Center for Health Statistics [1] places the number of profoundly deaf in the U.S. at more than 400,000, while people classified as hard-of-hearing number over 20 million, or about 8 percent of the total population. More statistics data on Vital and Health Statistics Series 10, No. 200: Over 8 million Americans have visual impairments (1996) Approximately 22 million Americans are hearing-impaired (1996) Furthermore, as the Section 508 of the Federal Rehabilitation Act in the United States passed, which says the U. S. government should stop purchasing any information technology that is inaccessible to people with disability, , there will be more and more attention given to concerning universal usability design of a web site. For those who are deaf or hard of hearing, audio content is not accessible. Videos without descriptions are not accessible to the blind. For those who are deaf and blind, text equivalents for audio/video can be easily transformed into Braille display [4]. In all cases, the information needs to be provided in an alternative format. Solutions include putting audio files into text format (using out takes if necessary) and using text descriptions for the audio portions of a video clip. Important information conveyed with the audio or video also needs to be available in text. These alternative formats and captions are also used frequently by those who:

• Have hardware or environment limitations.
  • Users may lack a sound card and speakers in their computers.
  • Users may be using a low-resolution display device to view the web content. As a result, the video content may not be displayed properly. For example, WAP and PDA users and low-income users.
  • Users may be using a low-bandwidth device to view the web content. They may just want to know the alternative text conveyed with the audio/video instead of downloading the whole audio/video content. For example, WAP and PDA and low-income users.
• Want to learn a second language.
  • Users may need captions on an audio/video clip to learn a second language.
• View or hear in a noisy environment.
  • Users may be in a noisy environment and be unable to listen to the audio clearly.
• Other reasons.
  • The captions on a video can be selected when the audio would be distracting to others in the area.
  • Users may be using a low-resolution display device to view the web content. As a result, the video content may not be displayed properly. For example, WAP and PDA users and low-income users.
  • The lack of quality when recording audio for the web. No matter how good your speakers are, if the recorded quality is not good, your product will not be acceptable to your audience.