Techniques for WCAG 2.0

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SM7: Providing audio description in SMIL 2.0

Important Information about Techniques

See Understanding Techniques for WCAG Success Criteria for important information about the usage of these informative techniques and how they relate to the normative WCAG 2.0 success criteria. The Applicability section explains the scope of the technique, and the presence of techniques for a specific technology does not imply that the technology can be used in all situations to create content that meets WCAG 2.0.


Applies whenever SMIL 2.0 player is available

This technique relates to:


The objective of this technique is to provide a way for people who are blind or otherwise have trouble seeing the video in audio-visual material to be able to access the material. With this technique a description of the video is provided via audio description that will fit into the gaps in the dialogue in the audio-visual material.


Example 1: SMIL 2.0 audio description sample for RealMedia player

Example Code:

<smil xmlns="">
      <root-layout backgroundColor="black" height="266" width="320"/>
      <region id="video" backgroundColor="black" top="26" left="0" 
      height="144" width="320"/>
      <video src="salesdemo.mpg" region="video" title="Sales Demo" 
      alt="Sales Demo"/>
      <audio src="salesdemo_ad.mp3" begin="33.71s" title="audio description" 
      alt="Sales Demo Audio Description"/>

The example shows a <par> segment containing an <audio> and a <video> tag. The audio stream is not started immediately.


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  1. Find method for turning on audio description from content/player (unless it is always played by default)

  2. Play file with audio description

  3. Check whether audio description is played

Expected Results

If this is a sufficient technique for a success criterion, failing this test procedure does not necessarily mean that the success criterion has not been satisfied in some other way, only that this technique has not been successfully implemented and can not be used to claim conformance.