The successful synchronization of multimedia content, especially audio and video, is essential to accessible web-based communication and cooperation. Understandable media is therefore media synchronized to very specific limits, according to multiple research studies. By clarifying the parameters of adequate synchronization we can influence the development of future technologies, specifications, and accessibility guidelines.
Providing an accessible multimedia experience requires that distinct media resources be presented concurrently. The timing and presentation of each must support comprehension. Put differently, the distinct media resources must not be allowed to drift out of synchronization. However, if they do, they must not go beyond very specific tolerance levels.
In preparing this document, we review the research literature to clarify the ranges of acceptable tolerances. This is important, as slips outside these ranges can cause loss in comprehension for the user. Research shows that people will not understand media when its components fall outside specific synchronization tolerances. For comprehension of media across multiple formats, accessible multimedia requires that its component parts remain within research validated synchronization tolerances. These components may be audio, video, captions, sign language interpretation, and descriptions of video content.
The Research Questions Task Force (RQTF) of the Accessible Platform Architectures (APA) Working Group is actively looking at identifying these tolerances and seeking to give informed answers to this question. For example, how much delay can occur between any related audio and video tracks? What are acceptable tolerances between speech and captions before comprehension is adversely affected? To find out, the Research Questions Task Force investigated what timing tolerances are appropriate in different circumstances and for different components of accessible multimedia.
The findings are summarized in the first public working draft of Synchronization Accessibility User Requirements (SAUR). Ultimately, the results are expected to be considered in the development of Web technologies for multimedia. They are also of interest for purposes of future development of W3C/WAI accessibility guidelines. In addition, this work is relevant to multimedia systems, including real-time communication applications.
We welcome your feedback!
Review and comments on the draft are encouraged. The Task Force welcomes additional research-based evidence, comments on the document, and responses to the editor’s notes included in the draft.
This work is supported by the EC WAI-GUIDE Project.