Guideline 1.2: Time-based Media

Provide alternatives for time-based media

You can use this guideline both for time-based media and synchronized media (with another format and/or time-based interactive components), including:

  • only audio
  • only video
  • audio and video combined
  • audio and/or video combined with interaction

Best practices

  • Prerecorded audio: Provide an alternative that presents equivalent information for prerecorded audio-only content.
  • Prerecorded video: Provide either an alternative for time-based media or an audio track to present equivalent information for prerecorded video-only content.
  • Prerecorded synchronized media: Provide an audio description or media alternative.
  • Prerecorded audio in synchronized media: Provide captions, and if possible, also sign language interpretation.
  • Live audio content in synchronized media (Live): provide captions.
  • Prerecorded video content in synchronized media (): Provide an audio description.
  • Embed interactive elements (for example links) in the alternative content where appropiate.

1.2.1 Prerecorded audio only and prerecorded video only Level A

For prerecorded audio-only and prerecorded video-only media, the following are true, except when the audio or video is a media alternative for text and is clearly labeled as such:

  • Prerecorded Audio-only: An alternative for time-based media is provided that presents equivalent information for prerecorded audio-only content.
  • Prerecorded Video-only: Either an alternative for time-based media or an audio track is provided that presents equivalent information for prerecorded video-only content.

Compulsory

  • Provide an alternative for time-based media for prerecorded audio-only content or prerecorded video-only.
  • Provide audio that describes the important video content and describing it as such.

Recommended

  • Provide a transcript of an audio only presentation.
  • Link to textual information that provides comparable information (e.g., for a traffic Webcam, a municipality could provide a link to the text traffic report.)

Failures

  • Alternative text that are not descriptive. E.g. alt="spacer", alt="icon.jpg" or alt="image".
  • Long descriptions that does not present the same information.

1.2.2 Captions for prerecorded audio content Level A

Captions are provided for all prerecorded audio content in synchronized media, except when the media is a media alternative for text and is clearly labeled as such.

Compulsory

  • Provide open (always visible) or closed captions.

Recommended

  • If the clip has no sound, provide a note saying “No sound is used in this clip”.
  • If there are audio tracks for different languages, provide captions using SMIL.

Failures

  • Captions omitting some dialogue or important sound effects
  • Synchronized media without captions when the synchronized media presents more information than is presented on the page
  • Not labeling a synchronized media alternative as an alternative.

1.2.3 Audio Description or Media Alternative (Prerecorded) Level A

An alternative for time-based media or audio description of the prerecorded video content is provided for synchronized media, except when the media is a media alternative for text and is clearly labeled as such.

Compulsory

  • Provide an alternative for time based media linking to the alternative for time-based media immediately next to the non-text content; or using the body of the object element
  • Provide a second, user-selectable, audio track that includes audio descriptions
  • Provide a version of a movie with audio descriptions using SMIL or using any player that supports audio and video
  • Provide a movie with extended audio descriptions using SMIL or using any player that supports audio and video

Recommended

  • Use SMIL to provide audio description in multiple languages

1.2.4 Captions (Live media) Level AA

Captions are provided for all live audio content in synchronized media.

Compulsory

  • Create captions for live synchronized media and provide open (always visible) captions.
  • Create captions for live synchronized media and closed captions using any readily available media format that has a video player that supports closed captioning.
  • Create captions for live synchronized media and provide closed captions using SMIL.

1.2.5 Audio Description (Prerecorded media) Level AA

Audio description is provided for all prerecorded video content in synchronized media.

Compulsory

  • Provide a second, user-selectable, audio track that includes audio descriptions
  • Providing a version of a movie with audio descriptions using SMIL or using any player that supports audio and video.
  • Provide a movie with extended audio descriptions using SMIL or using any player that supports audio and video.

Recommended

  • Provide audio description in multiple languages in SMIL.
  • Provide audio description for live synchronized media.

1.2.6 Sign Language (Prerecorded media) Level AAA

Sign language interpretation is provided for all prerecorded audio content in synchronized media.

Compulsory

  • Include a sign language interpreter in the video stream
  • Provide a synchronized video of the sign language interpreter that can be displayed in a different viewport or overlaid on the image by the player using SMIL.

Recommended

  • Use metadata to associate sign language alternatives of a video to enable choice of sign language. E.g. provide, in metadata, URI(s) that point to several English sign language translations (ASL, SASL, BSL, Auslan, ISL, NZSL) of a Web page.

1.2.7 Extended Audio Description (Prerecorded media) Level AAA

Where pauses in foreground audio are insufficient to allow audio descriptions to convey the sense of the video, extended audio description is provided for all prerecorded video content in synchronized media.

Compulsory

  • Provide a movie with extended audio descriptions using SMIL or using any player that supports audio and video

Recommended

  • Add extended audio description in multiple languages in SMIL.

1.2.8 Media Alternative (Prerecorded media) Level AAA

An alternative for time-based media is provided for all prerecorded synchronized media and for all prerecorded video-only media.

Compulsory

If the content is prerecorded synchronized media:
  • Place a link to the alternative for time-based media immediately next to the non-text content OR
  • Link to the alternative using the body of the object element
If the content is prerecorded video-only:
  • Provide an alternative for time-based media for video-only content

Recommended

  • Use noembed with embed (HTML)
  • Provide a corrected script
  • Add detail to audio description

Failures

  • Not labeling a synchronized media alternative to text as an alternative

1.2.9 Audio-only (Live media) Level AAA

An alternative for time-based media that presents equivalent information for live audio-only content is provided.

Compulsory

  • Provide a link to a text transcript of a prepared statement or script if the script is followed
  • Provide text based alternatives for live audio-only content
  • Incorporate a live audio captioning service into a Web page

Recommended

  • Use metadata to associate text transcriptions with audio-only conten. E.g. provide, in metadata, URI(s) that point to several text transcripts (English, French, Dutch) of an audio file.

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