Accessible web design		Content & navigation • HTML • Interactive & other media • WebCT accessibility issues • Validation

Interactive & other media

Accessibility issues abound in the use of embedded media and plug-ins. The media types discussed here are: PDF, Powerpoint, Flash & Shockwave and video & audio.

Problems with Plug-ins

Problems for users with disabilities include inaccessibility of content within the object displayed by the plug-in, and interference or incompatibility with the assistive technology that is being used.

Although many plug-in technologies do not make it possible to create fully accessible content, it is important for developers to make the content as accessible as possible. Guidelines developed by WebAIM can increase the accessibility of plug-in content - these guidelines are similar to those relating to development of all types of web content, and are, in summary:

1. Provide support for the plug-in
2. Don't require a mouse
3. Use good keyboard shortcuts
4. Provide captions for all audio content
5. Don't cause a seizure
6. Use icons and other navigation mechanisms consistently
7. Use good color contrast

See http://www.webaim.org/Articles/plugins.php for a full description of guidelines.

PDF

Adobe Acrobat PDF (Portable document format) is a common format for distributing documents electronically. It has the advantage of preserving formatting and embedding fonts, as well as being non-editable, and is accessed with a freely distributed plugin, Acrobat Reader.

Acrobat Reader 5.0 allows screen readers to access appropriately formatted PDF documents. However, not all users have this version installed, and not all PDF documents are text-based (some are scanned in as graphics), which renders them useless to many assistive technologies.

It is recommended that an accessible HTML version be made available as an alternative to PDF, which may require that images scanned as graphics be processed using OCR (optical character recognition) software for conversion to text.

Adobe Capture (http://www.adobe.com/products/acrcapture/main.html) has the ability to convert image files to tagged PDF files, also see Adobe's website for more information on accessibility features: http://access.adobe.com/information.html).

Guidelines for Accessible Online Courses (link from EDTeC website) shows how to make PDF documents accessible.

PowerPoint Presentations

PowerPoint has the ability to export as HTML, but these documents are problematic for assistive technologies. To make a PowerPoint slide show fully accessible requires their conversion to HTML using Word or a web-authoring tool.

Guidelines for Accessible Online Courses (link from EDTeC website) shows how to make Powerpoint documents accessible.

WebAIM suggests the use of this "Save as accessible HTML" Powerpoint plug-in, with the proviso that: "This plug-in is still under development, so there is room for improvement": http://www.rehab.uiuc.edu/ppt/.

See http://www.webaim.org/howto/powerpoint for more information on accessible conversion of Powerpoint files.

Flash/Shockwave

Macromedia Flash and Director are popular applications for the production of interactive and animated elements, allowing compact and complex interactivity that is extremely technically accessible (works on any platform with the freely provided Flash or Shockwave player plugin). They do however present accessibility issues for disabled users, with all content (text, video, audio) embedded in the 'object' and not accessible to assistive software.

See http://www.macromedia.com/macromedia/accessibility/features/flash.html for Flash features that support accessibility.

Macromedia also provides design guidelines (http://www.macromedia.com/software/flash/productinfo/accessibility/guidelines/) and developer techniques (http://www.macromedia.com/software/flash/productinfo/accessibility/flash_techniques/) which go some way towards addressing inherent accessibility problems.

Also see HTML4.0 for the use of the OBJECT element to specify alternative content.

Video/audio

For audio or video content, it is necessary to provide some equivalent information for those who cannot access the visual or auditory content. The provision of images and sounds is beneficial to many students who may have difficulty reading text, so that information displayed visually can make content more accessible. To ensure accessibility of multimedia elements consider the following points:

1. Include subtitles for video if there is no sound track.
2. Provide an auditory description of the important information of visual multimedia (e.g. images, animations, applets, video)
3. Provide a text document to accompany audio.

Media technologies behave differently, depending on whether the media object is embedded in the web page or accessed as a standalone element. See: 'To Embed or Not To Embed - A Comparison of Media Player Technologies': (http://www.webaim.org/Articles/embeddedmp.php) which compares Windows Media Player, QuickTime and RealMedia Player.

Options for accessibility:

The main formats that can be used to produce acccessible media for the web are:

The Synchronized Multimedia Integration Language (SMIL) specification was created to allow developers to integrate independent media objects into a synchronized multimedia presentation. SMIL affords authors the means to make their multimedia presentations accessible by incorporating captions, audio descriptions, and subtitles which the user can toggle on or off and which are synchronized with the other media elements. The SMIL specification is maintained and updated by the W3C.
An overview of how SMIL works: http://www.helio.org/products/smil/tutorial/

QuickTime (developed by Apple) is a powerful, yet easy to use, tool for authoring and viewing content. QuickTime supports SMIL 1.0, but also allows developers to easily add caption, subtitle, and audio description tracks in its native format.
The Apple Quicktime website provides a variety of Quicktime tutorials: http://www.apple.com/quicktime/products/tutorials/
This NCAM tutorial describes how to add a caption track in Quicktime: http://ncam.wgbh.org/richmedia/qtcapshowto.html

SAMI (Synchronized Accessible Media Interchange) is Microsoft's specification for adding captions to online media. It supports a variety of features for captioning, but is used only by the Windows Media Player.
Microsoft's SAMI homepage: http://www.microsoft.com/enable/sami/default.htm

RealNetworks uses SMIL 1.0 in order to make its media accessible. RealText, RealPix, RealAudio, and RealVideo can all be referenced from a SMIL file and synchronized with one another.
More information in the RealSystem Production Guide: http://service.real.com/help/library/guides/production8/realpgd.htm

XHTML+SMIL (formerly known as HMTL+TIME)
Microsoft's Internet Explorer 5.5 for WIndows supports a version of SMIL 2.0 called XHTML+SMIL. Authors can create presentations that take advantage of new accessibility features of SMIL 2.0 such as extended audio descriptions in addition to the ability to easily include text captions.
HTML+TIME (Timed Interactive Multimedia Extensions), first released in Microsoft® Internet Explorer 5, adds timing and media synchronization support to HTML pages. http://msdn.microsoft.com/library/default.asp?url=/workshop/author/behaviors/time.asp

More information on these formats are available at the National Center for Accessible Media - Resource Center for Developers of Rich Media (http://ncam.wgbh.org/richmedia/index.html). A variety of tools and tutorials are available at: http://ncam.wgbh.org/richmedia/learning.html. Media Access Generator (MAGpie) - NCAM's free software for adding captions to QT, SMIL and SAMI media files is available at: http://ncam.wgbh.org/webaccess/magpie/.

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