Web checklist

The purpose of this checkpoint is to enable deaf people and people with hearing impairments to access audio portions of multimedia. Captions are text on the screen that identify speakers, dialogue, music, and sound effects. Captions fall into two types:

• Open captions are burned into the image, similar to subtitles, that the user cannot turn off.
• Closed captions are a separate data stream that is synchronized with the multimedia. The user can turn these captions on or off.

To comply with this checkpoint, you must meet at least one of the following techniques.

1. Open captions: Provide open (always visible) captions.
2. Closed captions: Provide closed captions.

Note: The examples presented in the techniques are not exhaustive. They are meant to illustrate the spirit of this checkpoint.

General examples

1. Open captions: Provide open (always visible) captions.

   To comply with this technique, you must implement the following example.

   General example 1

   Open captions are embedded into the multimedia presentation. The captions are burned into the video image and users cannot turn them off. The advantage to this type of captioning is that additional software or technology is not needed to view the captions. The open captions can be placed on any video stream, regardless of whether or not the technology supports closed captioning. The disadvantage of open captions is that users do not have the ability to turn them off, so users without visual or hearing impairments will see the dialogue in addition to hearing it from the audio track.

   An example of captions embedded into the video stream is shown in the screen shot below. As the captions run automatically when the video is playing, the user does not have the option of turning off the captions.

   

   For additional information, refer to the WCAG 2.0 examples of providing open captions (link resides outside of ibm.com).

   Required unit tests for general development technique 1

   Manually perform the following unit tests.

   • Locate the multimedia object.
   • Watch the multimedia and ensure that embedded open captions are visible, in sync with the multimedia, and that the captions identify all speakers, describe all of the dialogue, music, and important sound effects.

2. Closed captions: Provide closed captions.

   To comply with this technique, you must implement the following example.

   General example 2

   Closed captions are usually created as a stream of data that runs in parallel with the multimedia. A user can turn these captions on or off. Closed captions must be provided using any readily available media format that has a video player, is free of charge and supports closed captioning.

   An example of a multimedia presentation that contains captions is shown in the screen shot below. The "cc" button at the bottom of the screen allows the user to turn the captions on or off.

   

   You can use SMIL 1.0 and SMIL 2.0 to create closed captions for a variety of different media players. For a detailed list of players that support SMIL 1.0 and SMIL 2.0, refer to the W3C Synchronized Multimedia (link resides outside of ibm.com) page.

   For additional information, refer to the WCAG 2.0 examples of providing closed captions (link resides outside of ibm.com).

   Required unit tests for general development technique 2

   Manually perform the following unit tests.

   • Locate the multimedia object.
   • Watch the multimedia with closed captions turned on and verify that the captions are visible, in sync with the multimedia, and that the captions identify all speakers, describe all of the dialogue, music, and important sound effects.

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Adobe^® Flash^® examples

For techniques that have no Flash-specific examples, refer to the general examples for guidance.

1. Open captions: Provide open (always visible) captions.

   There are no specific examples for implementing this technique in Adobe^® Flash^®. Use the general examples as a guide.

2. Closed captions: Provide closed captions.

   To comply with this technique, you must implement the following example.

   Flash example 1

   For movie clips and other meaningful Flash objects, include a full description of the action taking place in the clip. Do not rely on subtitles only because they do not adequately describe all of the action on the screen. In addition, provide audio playback controls so that users can control the speed, volume, and navigation of audio clips. Review Checkpoint 2.1a Keyboard Functionality to ensure that all controls are keyboard accessible.

   Required unit tests for Flash development technique 2

   Refer to the required unit tests for general development technique 2.

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Although you do not have to implement the following recommended techniques in order to comply with this checkpoint, you should review them because they can improve the accessibility and usability of the application.

1. Ensure your captions adhere to the standard captioning guidelines.
2. Provide a note stating "No sound is used in this clip" for video-only clips.
3. Use SMIL 1.0 to provide captions for all languages present in the audio tracks.
4. Use SMIL 2.0 to provide captions for all languages present in the audio tracks.
5. Provide a pop-up text window for a short audio presentation.

Recommended development technique 1 examples

Ensure your captions adhere to the standard captioning guidelines. For example:

• Provide information at the beginning of the movie (or with the link to the movie) that describes the type of captioning used (open or closed), and describes the language of the captions.
• Add captions to the bottom of the movie or object. Ensure that the captions do not block any important action in the movie. The captions should enhance the movie, not detract from it.
• Ensure that the captions do not display more than three lines at one time.
• Follow sentence capitalization and proper punctuation standards and use italics to emphasize words or sentences.
• All spoken text should be included in the caption and the captions should be synchronized with the video and spoken text.
• Use high contrasting colors and easy-to-read, sans-serif fonts for the captions.
• Place the speaker name in front of the caption each time a speaker changes.
• Include information about background sounds, music, and other relevant information in parentheses. However, do not describe someone's physical appearance or race, unless those aspects are germane to the understanding of the video material.

Note: The examples for recommended development techniques 2-6 are currently under development by the WCAG 2.0 Working Group.