Description of visual information

Overview – Description of visual information

An audio track or descriptive transcript describes the visual information needed to understand video content including actions, characters, scene changes, and on-screen text that are important and are not described or spoken in the main sound track. For example, “David passes an envelope to Eric. Eric opens it and frowns.” Description benefits users who are blind and others who cannot see the video adequately.

Do you need description of video?

Audio description

For pre-recorded media:

• Video with audio requires audio description
• Video-only requires audio description or a descriptive transcript

For live media broadcasts on the web:

• Video with audio do not require audio description
• Video-only do not require audio description

Note: There is no need for audio description if the video is designed with integrated descriptions (see audio methods, below).

Descriptive transcript

For pre-recorded media:

• Video with audio requires a descriptive transcript.
• Video-only requires a descriptive transcript or audio description.
• Audio-only content requires a basic transcript.

For live media broadcasts on the web:

• Video with audio Transcripts are not applicable for live video (live captions are required)
• Video-only may have a descriptive transcript (optional).
• Audio-only requires either basic transcript or captions.

The four methods of providing audio description

In order of preference, these are the four methods of providing audio description:

1. Integrated

   New videos are scripted so that the speaker describes the visual information. No separate description is needed. When writing the script, ensure all relevant visual information is included. For instance, a speaker presenting a chart provides the key information, such as:

   “The chart compares physical activity pre-COVID and post-COVID for three age groups. Youth, aged 12 to 17, reported less physical activity; adults, aged 18 to 64, reported the same amount; older adults, aged 65+, reported more physical activity.”

2. Timed text file

   If the video player supports description from a text file, provide a timed text file. The description must fit in the space of the main audio, or the player must provide functionality to pause during the description. Write out the descriptions and add timestamps in the file format used by the player (see the example VTT format, below).

3. Separate audio file

   If the video player supports a separate audio track for description, and if there’s enough space in the main audio for it, provide description in a separate audio file. Ensure the descriptions play in the audio spaces within the main video. Provide a captions file of the description.

4. Separate described video

   Otherwise, provide a separate described video. Write and record the descriptions, then create a new audio file by combining the original audio with the new description audio.

   • If the descriptions fit in the spaces and if your media player uses separate video and audio tracks, you’re finished. If your player uses a single video that includes the audio, generate a new video with the audio you just created.
   • If the descriptions don’t fit in the spaces:
     • If you can extend the scenes with extra footage from the original shoot, recut the video to fill in the visual space where you need time for description.
     • If you can’t extend the scenes, leave a static image in the video while the description is playing in the audio, aka Extended video description.

<video […]>
   <track kind="descriptions" label="English audio descriptions" src="descriptions.vtt" srclang="en">
</video>

Writing descriptions

Many organizations choose to outsource their description. If you are attempting it yourself, bear these tips in mind:

• Describe the visual elements important to understand what the video is communicating.
• Describe objectively. Do not interpret, censor or comment.
• Write in present tense, using an active voice and a third-person narrative style.
• Include all text, e.g., title text at the beginning, links and email addresses, speaker’s names, and text in a presentation.

Transcripts are either static or interactive and timestamped, depending on the design:

• Static transcripts, unlike audio description, don’t have to fit the description into gaps in the audio. Static descriptions may use as many words as is necessary for clarity.
• Interactive transcripts use timestamps in the captions and descriptions timed text files to fit descriptions into the gaps in audio of the main video. These descriptions are constrained by the time available and include less detail than descriptions in static transcripts. Alternately, the media player may offer an option to pause the video while descriptions are announced, in which case the descriptions don’t have to fit into the gaps in the audio of the main video.

This is a shortlist of requirements. The Descriptions Key website offers more best practice for authoring descriptions.

Related WCAG resources