Techniques for WCAG 2.0

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FLASH9: Applying captions to prerecorded synchronized media

Applicability

Adobe Flash-based Content

This technique relates to:

Description

The objective of this technique is to provide an option for people who have hearing impairments or otherwise have trouble hearing the sound and dialogue in synchronized media to be able to choose to view captions as an alternative to audio information. With this technique all of the dialogue and important sounds are provided as text in a fashion that allows the text to be hidden unless the user requests it. As a result they are visible only when needed. This can be achieved using the FLVPlayback and FLVPlaybackCaptioning components. Note: when using FLVPlayback skins the closed caption button is accessible by default, but if implementing custom skins authors need to test to verify that the button is accessible.

Examples

Example 1: Adding a timed text caption file to Flash

  1. Use an external tool (such as Magpie or a simple text editor) to create a timed Text captions xml file. Stop and play the video content, and for each relevant part of audio information (including speech, important background noises and event sounds) include the start and end time code as well as the textual alternative. Tools like Magpie have advanced features to make this process easier, whereas a text editor requires you to read the timecodes from your media player and include them in the XML as illustrated in the sample captions document below

  2. In Flash, create a new instance of the FLVPlayback component on your stage, and set its contentPath value to your flv video file using the 'Component inspector' or 'Parameters' panel.

  3. Set the 'Skin' parameter to use a skin which includes the CC (closed captions) button.

  4. From the components list also create an instance of the FLVPlayback captioning component. In the 'Component inspector' panel set its 'Source' parameter to the name of your timed text xml file. The captions will automatically placed at the bottom of the player's frame.

Example Code:

<?xml version="1.0" encoding="UTF-8"?>
<tt xmlns="http://www.w3.org/2006/04/ttaf1"
      xmlns:tts="http://www.w3.org/2006/04/ttaf1#styling" xml:lang="en">
  <head>
    <styling>
      <style id="defaultSpeaker" tts:fontSize="12" tts:fontFamily="SansSerif" tts:fontWeight="normal" tts:fontStyle="normal" tts:textDecoration="none" tts:color="white" tts:backgroundColor="black" tts:textAlign="left" />
      <style id="defaultCaption" tts:fontSize="12" tts:fontFamily="Arial" tts:fontWeight="normal" tts:fontStyle="normal" tts:textDecoration="none" tts:color="white" tts:backgroundColor="black" tts:textAlign="center" />
    </styling>
  </head>
  <body id="thebody" style="defaultCaption">
    <div xml:lang="en">
      <p begin="0:00:00.20" end="0:00:02.20">If there were nothing <br />
in our universe</p>
      <p begin="0:00:02.20" end="0:00:05.65">the fabric of space-time <br />
would be flat.</p>
      <p begin="0:00:05.65" end="0:00:08.88">But add a mass, <br />
and dimples form within it.</p>
      <p begin="0:00:16.61" end="0:00:19.84">Smaller objects that <br />
approach that large mass</p>
      <p begin="0:00:19.84" end="0:00:23.41">will follow the curve <br />in space-time around it.</p>
      <p begin="0:00:32.64" end="0:00:36.84">Our nearest star, the sun, <br />has formed such a dimple</p>
      <p begin="0:00:36.84" end="0:00:38.00">and our tiny planet Earth</p>
      <p begin="0:00:38.00" end="0:00:41.50">goes along for the ride <br />in the curve of its dimple</p>
      <p begin="0:00:41.50" end="0:00:43.80">staying in orbit <br />around the sun.</p>
      <p begin="0:00:45.67" end="0:01:55.00"></p>
    </div>
  </body>
</tt>

Resources

Resources are for information purposes only, no endorsement implied.

http://ncam.wgbh.org/webaccess/magpie/

http://www.buraks.com/captionate/

http://www.w3.org/AudioVideo/TT/

Tests

Procedure

Watch all video content displayed by your Flash movie. Ensure that:

  1. Captions are available for all audio content, either turned on by default or as a user preference.

  2. The captions properly describe all audio information contained in the video.

Expected Results