We use the term “multimedia” to refer to audio, video, PDF and Flash: any content on the Web that is not text, HTML, or a graphic.
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Different people have different learning styles; every time you present your content in a different medium, you increase the accessibility of your site. Developing accessible sites does not mean making every type of media usable, it means making all the information available to everyone.
Multimedia can create some of the richest and most engaging experiences on the Web. For this very reason, it is also the most challenging aspect of web accessibility. The simplest rule to follow for rich media is: provide an alternative.
Audio
For audio, the accessibility alternative may be relatively simple; if the audio file in question is spoken word, it is sufficient to provide a text transcript. For music, provide lyrics and, if appropriate, a description of the piece and an explanation of its significance.
Audio can be used to benefit learning-disabled users. Consider offering a reading of key passages or especially difficult text. In returning to our original point that improvements made with accessibility in mind will help non-disabled users as well, consider how an audio reading will assist someone who is not fluent in the language. There are parts of language that are not well conveyed by text, such as correct pronunciation, and language flow.
Video
Video files are a great way to present information. These can be short video clips that you create yourself, or links to web-based videos that a peer has made. A Chemistry professor at San Francisco State University has created a captioned video showing each step of his lab experiments. He reports fewer questions about the procedures and positive feedback from students. If you use a video file that has no audio track, let your students know that there is no audio right in the link to the file (e.g., “Video of amoeba movement via temporary projections called pseudopods—no audio”). That way the students will know that they do not need speakers and deaf and hard of hearing students will know that they do not need captions.
When adding video to your site, accommodations need to be made for both vision and hearing-impaired users. For visually impaired users, audio description (AD) of the contents of a scene is important. In twenty-five words or less, an audio description is a narrator providing a spoken context for anything that the viewer cannot understand by listening to the soundtrack. For hearing impaired users, any key information provided in the video should be represented in the text equivalent. Perhaps in the picture there is a sign placed prominently that the viewer is expected to read, or people in the video are reacting to a sound heard off-camera. These details affect the viewer’s understanding of the material, and you need to ensure that all visitors to your site are able to get this information.
Transcripts VS. Captions/Subtitles
A transcript is one way that you can provide your audience with a second format for your content. Transcripts are easy, and can be created by anyone. If you are the creator of the video, chances are you have a script that you can provide. In some cases, a script may not need any modifications to be a full transcript. If you need to write a transcript from scratch, it isn’t hard, but it is time-consuming. Load up the video, and your word processor and get typing. Before long you will have a transcript to publish.
A transcript usually consists of one file with the whole content of the video. On the other hand, captions and subtitles are synchronized with the video stream, and as such require more effort, and time to create.
Note
You may want to consider using speech recognition software such as Dragon NaturallySpeaking. The authors of this chapter have had very good results with NaturallySpeaking. One of the big advantages of using speech recognition is that it keeps your hands free to do other things while transcribing, such as control the playback rate, and replay a section of the video). In some cases, you will find that transcription using speech recognition can actually be faster than manual input via the keyboard!
Captioning VS. Subtitling
Subtitles are a textual representation of the speech in a video clip. The focus of subtitles is to state what is said, not what is audible. Subtitling does not attempt to provide information about other aural cues, such as a ringing doorbell.
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If you wish to show a clip, which has dialogue in another language, consider captioning in your audience’s primary language! By doing this, you can aid language comprehension, for students that understand some of the primary language. For students that don’t speak the clip’s primary language, they will now be able to understand what is said in the video.
Captions attempt to provide a textual representation of all the audio in a video clip. This may include speech as well as sound effects (for example, a ringing doorbell) and background music. Writing video captions can come down to a matter of style. As with everything else in accessibility, you need to use common sense when making decisions about how much has to be captioned. Be thorough without overwhelming the user with unnecessary details.
If you are looking to provide a base level of enhancement, start with a transcript of the video. For a more interactive approach, subtitling or captioning can greatly increase the video’s comprehensibility for people who struggle with the language spoken. Reading the text while hearing the dialogue can be very helpful when learning a language.
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Open vs Closed Captioning: Closed captioning is a technology that an individual user enables, to see the captioning for a given video. Common applications of this are in: News broadcasting, and on VHS/DVD movies. With open captioning, the video’s picture has the textual representation directly ingrained into it. Users cannot choose whether they see the captions or not; they are always enabled. A common application of open captioning is for videos in another language.
Captioning is something that you can do yourself, but due to the amount of time necessary it may be more practical to hire a professional captioning company to caption your video. This can be expensive, but in the end you may find the price worthwhile. Video alternatives should be considered part of the cost of building and maintaining your site.
Flash
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Caution: Avoid building your entire website in Flash. Yes, you can make some visually impressive pages doing so. Yes, Flash sites can have a certain cool-factor, unachievable with HTML. It simply remains that most Flash sites are not as accessible as HTML sites.
Like all other forms of multimedia, Flash can improve accessibility for some users and degrade it for others. It can be easier to demonstrate concepts with interactivity and animation than with text and images. A well-designed Flash demonstration can have enormous benefits for students, especially those with learning disabilities. Yet it can be a problem for users with visual or physical handicaps. Some problem areas include:
- representing information only as graphics—see the discussion regarding images without alternative text
- small buttons, or buttons that cannot be navigated to using the keyboard—users with physical disabilities may have trouble using the interface
Flash and Screen Readers
Since Flash generally does not present text in a linear fashion, often screen readers cannot synthesize speech in a manner that makes sense to the user. Blocks of text can change over time, be randomized, and appear at differing locations of the screen. Users must also have an up-to-date screen reader that works with the current version of Flash.
When creating content in Flash for screen readers, keep the following questions in mind:
- Does the reading order make sense? Flash objects are read in the order in which they were created, rather than the order in which they appear visually on the screen.
- When an event occurs on the screen, does the screen reader start reading again from the start? You don’t want to bombard the user with repeated information (recall the discussion on navigation in the XHTML/CSS section above).
- Do you need to display your content in Flash, or will a standard web page do just as nicely?
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This doesn’t mean you should never use Flash. It means that if your entire site consists of three buttons and a block of text, Flash is probably overkill. If you want some special animations, consider making them in a JavaScript-enabled HTML web page. A screen reader will ignore the animations but can read any text-based information.
Adobe offers suggestions and best practices for accessibility in Flash and other products on their website at http://www.adobe.com/accessibility/.
Portable Document Format (PDF)
The primary challenge of PDF files is to make sure that the text of your document is encoded as text, not as a graphic. If you scan a document onto your computer and directly output it to a PDF file, the contents of the file will be encoded graphically. If you want to create a PDF file from a text document you have scanned, be sure to use Optical Character Recognition (OCR) software. OCR software converts graphical lettering to text. PDF viewers (such as Adobe Reader) cannot analyze graphics for text, so this must be done when creating the PDF file.
The PDF format is used frequently online, but often unnecessarily. In many cases it is used to avoid creating a web page, or to ensure that the layout of the information is exactly as the designer wants it. In these cases, the information could be better conveyed in simple HTML, without forcing the user to download and view an extra file.
Of course, there are valid reasons to use the PDF format, which we will consider here.
Footnoting
HTML does not provide support for footnoting, or referencing. If you only need to cite one reference, including that information at the bottom of the web page may be sufficient. But if you are working on a document that requires extensive footnoting, the PDF format may be a better solution.
Annotating forms
If you require that other people fill out and return a form online, the PDF format has some extra features that may be useful. However, you should consider whether a web form with submission would accomplish your task.
Printing
The PDF format makes considerations for documents that are designed for reading on paper. HTML doesn’t, as it was designed to be a web/online format. As a result, HTML has no concept of print margins, page sizes, etc. Even the most savvy web designers will tell you that multi-column web pages can be quirky at the best of times.
Uneditable content
For official documents, journal articles and copyright-sensitive materials, PDF is often preferred as the end user is unable to make any edits or changes to the document.
There is a difference between wanting and needing to format your document using multiple columns. If you just want to use multiple columns, but it is not crucial to the information in the document, go brush up on your XHTML/CSS skills, and stay away from PDF. However, there are situations where the columnar layout and print format of the document is crucial, and in these cases usage of the PDF format is fine (e.g., academic articles, order forms).
Specialized notation
If you need to share a document with some specific notation (e.g., mathematics or another language), there are some specific technologies you should consider before jumping to PDF.
In the case of mathematics, if you are working on a file with fairly standard math notation in it, you may not need to use PDF: MathML might be enough. MathML is a specialized markup language developed by the W3C for displaying mathematics. The downside of MathML, is that your target audience must install the MathML fonts on their computer.
In the case of other languages, the Unicode character-encoding format may provide the characters you need. Fortunately, modern operating systems (Windows XP, Mac OS X) have support for Unicode built in.
If you need to display some other notation, PDF is probably a suitable choice, since it has roots as a graphical file format. The primary advantage of these other technologies is that the user does not have to launch a different piece of software to view your document. MathML and Unicode can be drawn natively in your audience’s web browser.
PDF and screen readers
Adobe Acrobat has been able to function as a screen reader since version 6. So for the purposes of testing your PDF files, checking what Acrobat says (literally) is the first point to test.
Tagging PDF files
Tags are extra information about the content of a document. Tags allow the document creator to specify alternative text of images, and to denote specific pieces of text as headings. Tags are similar to attributes in HTML—they provide extra information about an item in the document.
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Google for the URL of your PDF files. The HTML output that Google outputs is usually a fairly good indication of the accessibility of your PDF files. You should also try using the search function in your PDF viewer. If the search function works, chances are good that a screen reader will be able to interpret the text of the document. As with all other methods of validation, use it to check for technical problems only, then rethink the problem areas.
Adding tags in Microsoft Word (2000 or newer)
To add alternative text to a graphic:
- Right click on your image.
- Format picture.
- Go to the Web tab.
- Type your text under “Alternative Text”.
Specifying headings is also easy; just use the Word text style for headings. The added benefit for you, the document maintainer, is that now should you want to change the formatting of headers, you only have to change the formatting once. Using Word’s styles is akin to using Cascading Style Sheets (CSS) to format HTML pages.
When you are working on a document that requires multiple column formatting, use Word’s column function. Acrobat will automatically recognize the columnar arrangement, and correctly generate the reading order for software such as screen readers.
Full procedures for tagging are beyond the scope of this manual. For more information, Adobe provides a how-to guide on creating accessible PDF files (both from your initial source, and retrofitting) on their website (www.adobe.com/enterprise/accessibility/pdfs /acro7_pg_ue.pdf).
As with many other forms of accessibility, spending the time to increase the ease of use for disabled people improves the accessibility for other users as well. By adding tags to your PDF documents, now your documents are viewable on other devices, such as personal digital assistants (PDAs). Joe Clark wrote a very solid article on PDF accessibility, which discusses the appropriate usage of PDF files (at http://www.alistapart.com /articles/pdf_accessibility/).
