Blind and visually impaired users cannot see video on the web, so they require audio descriptions to be added to the video. However this can be a complicated process as many of the different media players that can play media files use many different file formats. Although each media player has universal file formats, each player also has their own specific file formats that can only be used on that particular media player. Sometimes files are only available in one file format so therefore the user is sometimes forced to use one particular media player in order to be able to view the file. Things are made even more difficult because the majority of media players are incompatible with screen readers.
Audio descriptions are recorded as a separate track and can be saved as a separate file, which can be inserted into pauses in the original soundtrack. The audio description may include information that describes the scene, the characters, the body language and any other visual elements that may be important to the understanding of the video this must be synchronised with the video. The WGBH at Boston provides a service where experts will be able to provide an audio description for a video. Audio descriptions cannot describe everything, so it is recommended that certain sounds be omitted from the description e.g. a bell ringing or laughter.
SMIL version 2.0 allows a web developer to expand or pause the video so that they can include long descriptions, but these features are not well supported by browsers. There are a number of American companies that offer to train people in how to make audio descriptions e.g. The VSA Arts of Texas.
Joe Clarke gives the following advice about writing audio descriptions.
If the audio file is a music file then it is recommended that the title of the song be included as an alt text. A long description or d -link can then be used to give additional information about the music file that is being played e.g. the type of music, its speed etc.
Web developers are obliged to provide accessible audio files under the DDA 1995. If a website only contains a small number of audio files, and audio files are not regularly added to the website then it is recommended that the methods described above be used. However if a website contains a large number of audio files and audio files are added to the website regularly then it is recommended that an external company be hired to manage the creation of audio descriptions. The web developer should also note that audio descriptions can also be added to Flash files.
If an accessible audio file cannot be provided, then it is recommended that a hyperlink to a full textual transcript of the audio file be included on the site as an accessible equivalent. It is recommended that this file be created in HTML or plain text format and both of these formats can be easily interpreted by screen readers.
SMIL was created in 1998 and is based on XML. It is the industry standard mark-up language for creating files for accessible media, including captioning for the deaf as well as audio descriptions. SMIL is recommended by the W3C it lets you cue text, audio and video together in any combination. It describes what appears and when. Support for SMIL is fairly good with Real Player and QuickTime 4.1 both supporting SMIL 1.0 but support for the new version of SMIL , SMIL 2.0 is poor.
SMIL allows a web developer to separate one whole file into several separate files e.g. audio, video, text and images. These separate files can then be sent to a users computer individually, therefore reducing the size of the multimedia file. The separate files can then be synchronised to display together as if they were one separate individual file.
It is recommended that a web developer code an SMIL file by hand, although this is very error prone it is considered necessary because there is no method currently available to automate this process. Graphical editing programs do exist that can automatically generate SMIL files, but these can produce code that is considered to be difficult to maintain. The best method of creating an SMIL file maybe to use graphical editing program to create the file and then edit the generated code by hand.
Microsoft has created its own version of SMIL called SAMI but it is only really supported by Windows Media Player and some of the SAMI documentation will not load in Internet Explorer. SAMI is only really a subset of the SMIL 2.0 guidelines, it resembles HTML but is considered to be difficult to learn snd unlike SMIL there are no graphical editing programs available that generate SAMI code. Therefore SAMI is only recommended if a web developer is attempting to add an audio description to a Windows Media Player file. If a web developer is trying to add an audio description to another other type of media player file format then SMIL is recommended. The World Wide web consortium have created a very useful tutorial for those wishing to learn more about SMIL . Meanwhile Microsoft have created a lengthy document the contains more information about SAMI .
MAGpie was developed by the WGBH in Boston. It can describe the contents of audio files and allows web developers to add captions to video’s for the deaf. It works with three different media players QuickTime by the Apple cooperation SMIL and SAMI. MAGpie allows web developers to record descriptions for audio files into the software. A web developer can then use MAGpie to attach the audio description that they recorded into the software to an audio file. More information about MAGpie. can be found on the WGBH website.