Providing sign language interpretation through synchronized video streams in SMIL 1.0

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 2.1 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 2.1.

Applicability

Applies whenever SMIL 1.0 player is available

This technique relates to Success Criterion 1.2.6: Sign Language (Prerecorded) (Sufficient as a way to meet G81: Providing a synchronized video of the sign language interpreter that can be displayed in a different viewport or overlaid on the image by the player).

Description

The objective of this technique is to provide a way for people who are deaf or otherwise have trouble hearing the dialogue in audio visual material to be able to view the material. With this technique all of the dialogue and important sounds are available in a sign-language interpretation video that is displayed in a caption area.

With SMIL 1.0, separate regions can be defined for the two videos. The two video playbacks are synchronized, with the content video displayed in one region of the screen, while the corresponding sign-language interpretation video is displayed in another region.

Examples

Example 1: SMIL 1.0 sign-language interpretation sample for QuickTime player

 
<?xml version="1.0" encoding="UTF-8"?>
<smil xmlns:qt="http://www.apple.com/quicktime/resources/smilextensions" 
  xmlns="https://www.w3.org/TR/REC-smil" qt:time-slider="true">
  <head>
    <layout>
      <root-layout width="320" height="300" background-color="black"/>
      <region top="0" width="320" height="240" left="0" background-color="black" 
      id="videoregion"/>
      <region top="240" width="320" height="60" left="0" background-color="black" 
      id="signingregion"/>
    </layout>
  </head>
  <body>
    <par>
      <video dur="0:01:20.00" region="videoregion" src="salesdemo.mov" 
      alt="Sales Demo"/>
      <video dur="0:01:20.00" region="signingregion" system-captions="on" 
      src="salesdemo_si.mov" alt="Sales Demo Sign Language Interpretation"/>
    </par>
  </body>
</smil>

Example 2: SMIL 1.0 sign-language sample for RealMedia player:

 
<?xml version="1.0" encoding="UTF-8"?>
<smil xmlns="https://www.w3.org/TR/REC-smil">
  <head>
    <layout>
      <root-layout background-color="black" height="310" width="330"/>
      <region top="0" width="320" height="240" left="0" background-color="black"
       id="videoregion"/>
      <region top="240" width="320" height="60" left="0" background-color="black" 
      id="signingregion"/>
    </layout>
  </head>
  <body>
    <par>
      <video dur="0:01:20.00" region="videoregion" src="salesdemo.mov" 
      alt="Sales Demo"/>
      <video dur="0:01:20.00" region="signingregion" system-captions="on" 
      src="salesdemo_si.mov" alt="Sales Demo Sign Language Interpretation"/>
    </par>
  </body>
</smil>

The example shows a <par> segment containing two <video> tags. The system-captions attribute indicates that the sign language video should be displayed when the user's player setting for captions indicates the preference for captions to be displayed. The <layout> section defines the regions used for the main video and the sign language interpretation video.

Resources

Resources are for information purposes only, no endorsement implied.

Tests

Procedure

  1. Enable control in content or player to turn on sign language interpretation (unless it is always shown)
  2. Play file with sign-language interpretation
  3. Check whether sign language interpretation is displayed

Expected Results

  • #3 is true