Video-only (no audio included): describe the relevant content of the video in an alternative text or provide an audio description as an audio file.
Audio description provides information about the events in the video for a blind or visually impaired person.
Video with an audio: add captions to the video. Include in the captions all sounds that are relevant for understanding the content. Tell the name of the speaker in the captions if multiple persons are speaking on the video and it is not clear who is speaking.
If all relevant information cannot be found in the audio track, provide an audio description, which describes the events of the video.
If the video is an alternative for text, ie. it includes the same content as the exercise description and it is marked as a media alternative, there is no need to provide an audio description or captions.
Please note that the audio description is an audio file and it is not possible to provide it as an alternative text for a video. Therefore all players can listen to it.