Accessibility of audio and video content on the web
I have re-published this content from a report I wrote for The Spoken Word Project in March 2007 - because it occurred to me that this might be useful information for organisations thinking of adding video to their websites.
Time constraints mean that this document cannot be considered a definitive review of the subject of accessible audio and video content - however it should provide information that can act as a starting point for your own research into the area.
Delivering audio and video on the web
There is no perfect solution to delivering accessible multimedia content on the web. The huge range of user needs, computer and software platforms and audio and video format available - ensures that no one solution will cover all accessibility needs.
The choices for any publisher of video will include,
- Sticking to creating content for a single player such as Windows Media Player, Quicktime or Flash.
- Publishing each resource in multiple formats in an effort to ensure no one is left out.
With the first option some users will not be able to play the content, as they do not have a compatible computer or software. The second option may lead to cost and resource implications for the publisher that can't be met - although if using tools that can export the resulting video in more than one format this is a route worth considering.
Some formats lend themselves to the creation of alternative content more than others. However, the most flexible or the most accessible format may not be the most widely used.
Youtube and the arrival of a new standard
The picture is complicated by the speed at which new 'standards' arrive on the web and changes in the functionality of existing formats, i.e., the extend to which a particular form is accessible changes as it is developed in line with new priorities. Flash is a case in point. Adobe reports the following statistics supporting its own case as the dominant player for web based video:
- Flash Player is on 97.3%
- Microsoft's Windows Media Player is on 83%
- QuickTime 66%, and
- Real 56%.
It is in Adobe's interest to report that their format is dominant, however this does appear to be the case in practice.
The rise of Flash for web delivery of video
There has been explosive growth in the availability and consumption of web video in the last couple of years - to the extent that a new dominant format has emerged. Flash has become the most popular way to deliver video on websites, certainly in relation to public consumption,
"in 2004 Flash Video was still a bit of a novelty. Two years later it is a standard. It is the video format of choice for two of the most popular sites on the web: YouTube and MySpace" Tom Green http://www.digital-web.com--the_rise_of_flash_video_part_1
According to Adobe-Macromedia, in less than one year Flash version 8 has been installed onto nearly 95% of the 765 million personal computers worldwide. The results is that "the Flash(R) 8 platform has grown faster than any other software in history." (See encodeflashvideo.com--default.aspx)
Flash and accessibility
Flash has traditionally been seen as an accessibility problem rather than a solution - but this is no longer the case. Web accessibility experts - on the contrary - are now recommending Flash as the most accessible way to deliver web video. Flash was the only answer forthcoming from several members of the Guild of Accessible Web Designers, when I posed the question on the mailing list about the best way to deliver accessible video.
However the rising dominance of Flash means problems for producers who want to serve up flash. My limited research indicates that Flash server software is expensive and not yet user friendly enough for use in a production environment. (see www.digital-web.com--the_rise_of_flash_video_part_2)
Andrew Kirkpatrick of Adobe had the following to say in reply to my questions about Flash Accessibility:
"For embedding video, you can make video with Flash more accessible than any other format.
You can provide captions for all media formats, but Flash provides access to the interface controls in a more robust way than other players (the typical advice for providing users withy access to the playback controls for other media players is to allow the media to load in the standalone player).
We have caption skins available for the Flash FLVPlayback component: blogs.adobe.com--captionskins.html
These currently work with Captionate for captioning, but will someday soon also offer support for DFXP captions.
Today, NCAM (the WGBH National Center for Accessible Media) released MAGpie 2.02, which includes support for DFXP captions. DFXP, by the way, is the W3C's new caption data format.
NCAM also released a new component for Flash that allows you to parse and display either DFXP or QT's caption format, and includes an API for caption searching. http://ncam.wgbh.org--ccforflash.html"
Granted he is speaking as a representative of Adobe, however, it is consistent with the views expressed by developers considering the most accessible format for delivering video on the Web.
Quicktime for video production
Quicktime continues to be the most appropriate solution for processing video prior to web consumption.
"The Flash video process starts with a source video--preferably a video in the QuickTime (.mov) format. There are two reasons behind this. The first involves the "GIGO Principle": Garbage In, Garbage Out. We shouldn't accept substandard artwork, audio, or other content, so it makes sense to apply those same quality standards to our video. The second reason is a matter of standards. The current industry standard is the QuickTime format, so it makes sense to request video in that format from your clients." http://www.digital-web.com--the_rise_of_flash_video_part_2
Serve video as both mp4 and flash?
Quicktime videos can be exported to Flash for delivery on the web. This provides the option of serving videos in both mp4 and Flash.
Technology can change quickly on the web, however in the short to medium term Flash can't be ignored as a potentially accessible vehicle for publishing video on the web.
My recommendation would be to consider either developing skills in-house in relation to Flash video development or to consider buying in a service that can provide assistance in developing resources in this area.
(See Niqui Merret Flash and Accessibility for further information, training and consultancy in relation to producing accessible Flash. www.niquimerret.com)
Audio in general is considered a highly accessible format, as it has benefits for print-impaired learners, such as people with dyslexia or blind or visual impaired users.
However, people who have a hearing impairment or who are deaf will have problems accessing audio. IMS Global Learning Consortium (see ncam.wgbh.org--sec5.html) outline the accessibility issues with audio as:
- lack of captions and/or transcripts.
- poor sound quality.
- inability to control volume.
Streaming versus downloads
Streaming is generally preferred to downloading because users with lower bandwidth connection can get quicker access to the content. Streaming may also be the preferred option in the educational context as many University and college computer labs do not permit students to save downloads to local hard disks.
Combining audio and text for greater accessibility
Accessibility can be enhanced by providing captions and/or transcripts. Provide users with the ability to control volume and providing visual equivalents to sound alerts (i.e., a beep). Further accessibility enhancements could include transcripts or captions or sign language.
A format that makes this possible is DAISY/NISO (Digital Accessible Information Systemes/Nation Information Standards Organisation). .DAISY/NISO allows simultaneous presentation of text, graphics and audio format. However, players for this format are not yet widely available.
With the DAISY/NISO format, text is provided in a XML document and the audio is syncronized with the text using SMIL (Synchronized Multimedia Integration Language). Benefits of the DAISY/NISO format include:
- Text and graphics can be provided along with the audio file.
- Text and audio descriptions of graphics can be incorporated.
- Navigation capabilities can be built in - allowing users to move around a document based on its structure.
The American Council of the Blind support the MAGPIE format,
"Individuals who read large print or have learning disabilities will also increasingly be able to benefit from reading files in this format. Currently, at least one reader allows people to control the font size or type, as well as change foreground and background colors to provide needed print contrast. People with learning disabilities are often able to track the text more easily when a player has an option to highlight words in the text while the user listens to the audio file." http://www.acb.org--accessible-formats.html
Links and resources
- A leading expert in relation to captioning and audio descriptions is Joe Clark
- Niqui Merret Flash and Accessibility expert. Provides training Flash Accessibility consulting.
- A good description of MAGPIE can be found at: http://www.acb.org--accessible-formats.html
- Captioning with MAGpie 2.0
- Guild Of Accessible Web Designers
- MAGPIE authoring tool to add captions, subtitles, and audio descriptions to digital media. This tool, MAGpie (Media Access Generator), is available from the National Center for Accessible Media (NCAM):
- CAST (the Center for Applied Special Technology) offers Tips on Presenting Alternatives to Sound.
- Proprietary software exists that allows authors to add sign language using animated characters. One company developing this software is Vcom3D. They have created "SigningAvatars" that are able to render content in Signed English and Pidgin Signed English (and possibly ASL in the future). More information is available from the Signing Avatar website.
- Creating Video and Multimedia Products that are Accessible to People with Sensory Impairments.
- ACCESSIBLE VIDEO IN A DIVERGING WEB ENVIRONMENT.
- Captionate Flash Vido Captioning Solution.
- The Rise of Flash Video, Part 1
- The Rise of Flash Video, Part 2
- The Rise of Flash Video, Part 3
- On2 Flix Software for Adobe Flash 8 and 9 allows editing of video using QuickTime-enabled applications - such as Apple Final Cut, Quicktime Pro.
- The Educational Applications of Streaming Audio: Accessible, Do-It-Yourself Multimedia.
- A Guide to Making Documents Accessible to People Who Are Blind or Visually Impaired by Jennifer Sutton.
- The DAISY Consortium
- Creating Audio Descriptions for Rich Media
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