Some reading systems can play multimedia clips. If you are including these you need to consider alternate versions for people with disabilities. A link to a transcript of video or audio material can be essential for users with a hearing impairment, and blind and partially sighted people will benefit from a description of an action happening in a video which isn't described in the audio track.
Audio description and captioning
Depending on the capabilities of the intended reading system and incorporated players both audio description and captioning can be applied to video clips to aid accessibility.
Audio description
Audio description integrates with any dialogue in the video clip to describe purely visual content which would not be perceived from the soundtrack alone. Typically, audio description would only be switched on by the purchaser if required.
Find out more about audio description.
Captioning
For people who find it difficult to hear what is being said on-screen captions provide a means of conveying the information. As with audio description, purchasers would only switch captions on if they needed to.
With both audio description and captioning purchasers who don't require these features would simply not turn them on as is the case where these features are incorporated into television programmes for example.
Information on the standards for subtitling is available from Ofcom.
Watch our video about incorporating audio and video in eBooks