Missing captions is a critical accessibility bug. It must be fixed immediately as it would block access for people with hearing impairements. Other users such as those accessing content with no sound on (that is very common these days) or those with accent barriers would also benefit with captions.
Captions are essential for any video
Whether or not your multimedia has audio, captions are essential.
For example —
If there is no sound, you’d need “[NO AUDIO]” as captions
If there is only music; no spoken words, you’d need “[MUSIC]” as captions
You could leverage tools such as YouTube’s automatic captioning to generate captions automatically but always validate the automatically generated captions because machine could interpret names or accents incorrectly and wrong captions are worse.
Consider your company policies about using external tools as those tools would “see” the video content to provide you the captions automatically.
Closed captions vs. Open captions
Closed captions are accessible instead of open captions that are embedded in the video graphics. Open captions also distort on large screen resolutions and cannot be accessed through screen readers.
Captions vs. subtitles
Captions in a language other than spoken words are subtitles. You’d want to provide captions in the language of the spoken words and, if needed, captions in additional language.
Additional video accessibility considerations
Descriptive audio / audio descriptions are a separate topic.
Consider providing transcripts.