Some people are unable to hear audio.
Therefore, audio content such as audio-recorded lectures or podcasts must be accompanied by a transcript, and videos must be provided with closed captions.
Some people are unable to see video.
Therefore, video must be carefully scripted or edited in a way that ensures all important content is accessible through the audio track. If this is not the case, any important information that’s presented visually must be described in a separate narration track using a technique called audio description.
Some people are unable to operate a mouse.
Therefore, multimedia content should be delivered in a player that can be operated with keyboard alone, and that has controls that are properly labelled so that they are announced properly to screen reader users, and can be operated effectively by speech input users.