Techniques for WCAG 2.0

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SM7: Providing audio description in SMIL 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