For all prerecorded video files there must be synchronized and accurate closed captions (CC).

What you need to know

• Closed captions (CC) are more than just subtitles. Subtitles merely convey dialogue. Closed captions also include any important sounds in the environment (sound effects) that are part of the story, for example, the sound of thunder, a door slamming, or background music.
• Closed captions require some amount of manual work, but there are a handful of free or inexpensive tools out there to make the process free or relatively cheap.

What you need to do

• Closed captions need to be added to your videos. For video-only, you may add an option to turn on an audio description within the video itself, or create a separate video with audio description.
• Make sure your closed captions sync up with the video and that they accurately convey the spoken words.
• Review and edit any automatic closed captions. You can’t count on those captions being completely accurate.

Reference

Read the full explanation of success criterion 1.2.2 on W3.org.

Related Resource

Check out “Captioning” from CSUN’s Universal Design Center for more information about this success criterion.