Let Closed Caption users know when a video has no audio

Not all videos have audio, but this isn’t obvious for people who use closed captions. These videos fall into two camps: decorative and instructive.

• Decorative videos are often used in the background of pages. They are short, perhaps three seconds long, and may loop. These don’t require a caption file.
• Instructive videos may include a short demonstration or a time-lapse video of a scene. They have no spoken words or environmental sounds. These should have a caption file, as there’s no indication that a person who uses closed captions is missing information.

With the guidance of Sarah Margolis-Greenbaum, I’ve created a sample caption file you can use with your videos: Generic No Audio Caption (Github). This caption file will display “[No audio]” at the 2 second mark and will appear for 3 seconds.

• VTT File: generic-no-audio.cc.vtt
• SRT File: generic-no-audio.srt
• Text version for videos hosted on Google Drive: generic-no-audio.txt

Don’t make viewers worry about missing audio information

Caption File Text

Caption files are specifically formatted text documents that contain a time stamp and the relevant audio information. These simple files tell video players to show “[No Audio]” from the 2 to 5 second mark.

WEBVTT
00:00:02.000 --> 00:00:05.000
[No audio]

Non-screaming screaming chicken

The generic caption file makes it clear that this screaming chicken is actually not screaming and is safe to play at the office or around your dogs.

The W3C has guidance on when captions are required.

Does My Media Need Captions?

This section tells you:

• What is required in the WCAG standard at Level A, AA, and AAA. (WCAG is introduced in the Planning page of this resource.)
• What is needed to meet user needs, beyond WCAG. If there are no “A”s, then it is not required in WCAG.

Audio-only (e.g., podcast):

• For pre-recorded:
• Captions are useful for people who are hard of hearing to get the richness of listening to the audio and fill in what they don’t hear well by reading the captions.
  Captions are not required to meet WCAG. (Transcripts are at Level A.)

For live:

• Captions are useful for people who are hard of hearing to get the richness of listening to the audio and fill in what they don’t hear well by reading the captions.
  Live text stream or accurate script of the audio available when live is in WCAG at Level AAA.

Video-only (no audio content):

• For pre-recorded and live:
• Captions are not needed because there is no audio information.

Video with audio content:

Does the video have audio information that is needed to understand what the video is communicating?

If no (for example, it is just background music):

• Captions are not needed because there is no important audio content. Consider informing users.

If yes:

• For pre-recorded:
• Captions are needed to provide the audio content to people who are Deaf or hard of hearing.
  Captions are required in WCAG at Level A.

For live:

• Captions are needed to provide the audio content to people who are Deaf or hard of hearing.
  Captions are required in WCAG at Level AA.