Skills for Access

Why this is important

Video normally contains a significant amount of visual and audio information, and understanding of the content requires access to both these channels. But people who cannot see the visual content of the video may as a result be unable to fully understand the video if visual or audio events happen and are not detectable or their context explained by the video's soundtrack. For example, someone in a video may make a facial expression which adds an ironic or sarcastic tone to what they say, but this important cue is entirely visual so would be missed by anyone unable to see the video. The same goes for some aural events - for example, if a character fires a gun, the gunshot will be heard, but anyone unable to see the film would not know who fired the gun without an additional explanation. Thus, the provision of audio descriptions - additional spoken audio information explaining or describing events - is necessary to enable understanding.

General Principles

Audio descriptions provide short pieces of spoken information to supplement the existing sound track of a media clip. This spoken information describes important visual events necessary to allow understanding of the media by someone who can only hear it. The number and extent of each individual audio description depends on the complexity of the visual component of the video.

They conventionally exist either as:

1. a number of short audio files or one file containing all descriptions, synchronised with the video clip as it plays, using a technology such as Synchronised Multimedia Integration Language, or
2. integrated into the soundtrack itself (in the case of Windows Media Player, this is the only option as Windows Media Player currently does not provide an additional audio channel).

The first option gives the potential for a user to turn on or off audio descriptions; the second by its nature means that audio descriptions will be 'open' to everyone.

Before you continue

The advice on this page helps you avoid introducing a specific accessibility barrier, but it's not a magic formula. To avoid attempting to follow a technical solution that is not appropriate to the resource and its intended purpose, you need to know the context in which the multimedia resource is being used:

1. The purpose or aim of the multimedia resource in question, and whether it is being used to supplement another resource in the learning environment, or whether its use is required by students.
2. The target audience, their knowledge and expectations, and the type of browsing and assistive technology that they may be using.
3. Whether the information and experiences provided by the multimedia technology are already available in an equivalent, alternative form.

For more background on this approach, see our Guide to the use of multimedia in accessible e-learning.

Technique Details

As with captioning, there is a degree of subjectivity to provision of audio descriptions, and there is a distinct lack of authoritative guidance on provision of audio descriptions. In fact the practice of providing audio described video over the web appears extremely rare, and this means that examples of good practice are few and far between. Multimedia accessibility expert Joe Clark recommends that for long, complex video content, seeking professional support to provide audio description remains the best option.

However, since providing some form of description is much better than none at all, Clark does also provide a useful set of principles that provide a solid framework for creating audio descriptions. These include the following (repeated here with permission):

• Describe what you observe.
• If time limits force you to be selective, first describe what is essential to know, such as actions and details that would confuse or mislead the audience if omitted.
• Whenever possible, describe actions and details that add to the understanding of personal appearance, setting and atmosphere.
• Descriptions are usually delivered during pauses or quiet moments. It is permissible to let pauses or quiet moments pass without a description. Conversely, since it is more important to make a production understandable than to preserve every detail of the original soundtrack, it is permissible to describe over dialogue and other audio when necessary.
• Describe as consistently as possible, using the same character names and terminology throughout a production or across several related productions, unless exceptions are warranted.
• Describe any obvious emotional states. Do not attempt to describe what is invisible, as a mental state, reasoning, or motivation.
• Deliver descriptions in a vocal style that melds into the surrounding audio at the point of the description.
• Narrators' voices must be distinguishable from other voices in a production, but they must not be unnecessarily distracting, as with recognizable celebrity voices.
• Read titles and credits wherever possible, including subtitles in a foreign-language production.
• Do not specify an exact passage of time unless indisputable visual evidence supports it.
• Describe in the language of the audience, not the production.

If you are intending to produce audio described video for e-learning purposes, it's recommended that you listen to as much audio-described material as you can find. Unfortunately there's not much to be found on the web - try NCAM's web site as a start. The Royal National Institute of the Blind (RNIB) do have for sale a number of audio described videos and DVDs. Cinemas occasionally show audio-described films; some terrestrial and satellite TV programmes are broadcast with audio descriptions, including the popular soap operas. Unfortunately, the only way to access these at present is through a specially-enabled digital TV set-top box (STB).

Normally audio descriptions should fit within periods of silence, or over quiet inconsequential; sound. However, in some cases, extended descriptions may be required - audio descriptions the length of which requires a temporary pause in the video. According to NCAM resources, this practice appears at present to be somewhat challenging given the current state of players and is probably beyond the scope of all but the most complex of video accessibility projects.

Given difficulties in creating and making available audio descriptions in multiple media players, rather than providing 'closed' descriptions ready to be enabled by the user, in some cases, the best solution may be to provide separate 'accessible' versions of the media:

1. Video plus audio
2. Captioned video plus described audio
3. Described audio as a sound file (for example MP3)

Techniques for creating and adding audio descriptions using specific media players are provided in separate How Tos.

Testing

The subjective nature of this accessibility technique, and a lack of formal, universally applicable guidelines makes it impossible to test using automated means. While watching the video from start to finish with audio descriptions will help you to check that all important visual events have been described, and that the addition of audio descriptions to the soundtrack does not adversely affect the quality of the soundtrack, feedback from end users is highly recommended, particularly people who are blind and severely visually impaired.