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What do you need to make audio and video accessible?
Creating Accessible Multimedia
There are two markup formats that support the inclusion of audio descriptions and/or closed captions in digital multimedia presentations- Synchronized Multimedia Integration Language (SMIL) and Synchronized Accessible Media Interchange (SAMI).
- SMIL is played by the QuickTime Player, RealPlayer, the Oratrix GRiNS Player and the Ambulant Player.
- SAMI is played solely by the Windows Media Player. A free utility, the Media Access Generator (MAGpie), can be used to create captions and audio descriptions for SMIL presentations, and captions only for SAMI and Adobe Flash presentations.
Synchronized Multimedia Integration Language (SMIL)
SMIL was developed by the World Wide Web Consortium (W3C), an international industry consortium that publishes protocols for the Web. SMIL 2.1 is the latest version of the specification, published in 2005. SMIL multimedia presentations are made up of elements-sound, video, pictures and text-that are stored separately and then synchronized at the time of playback. SMIL-formatted multimedia can be delivered via the Internet or a local file system via hard drive, CD or DVD. Visit the W3C's Synchronized Multimedia page for complete information about SMIL and related activities at the W3C.
When authored correctly, SMIL allows users to turn captions and descriptions on and off via a player interface. The QuickTime Player, GRiNS Player, Ambulant Player and RealPlayer each provide a menu selection or dialog box for this feature, but for better accessibility authors should consider adding accessible buttons to the player interface for easier toggling of tracks. In fact, this is crucial when embedding a player into a Web page. Below is a picture of caption and description buttons integrated into the QuickTime Player interface.
Take note that different SMIL players provide varying levels of implementation-- in other words, some players implement the entire specification, and some use only parts of it. Also, not all of SMIL's accessibility features are supported by all SMIL players. In these cases, we offer workaround solutions that will work with existing players.
Synchronized Accessible Media Interchange (SAMI)
SAMI is a Microsoft public specification that allows closed captions to be played in the Windows Media Player on the Windows OS only. When the Windows Media Player is used as a stand-alone player, viewers can turn the captions on and off using a menu selection. However, when the player is embedded in another application, such as a Web page, the developer must provide the toggling feature through a button in the application's interface. For additional flexibility, this interface can also provide options to change the font size or text color.
At the time of this writing, SAMI does not support closed audio descriptions. Instead, descriptions must be recorded permanently as open descriptions directly into a video's regular soundtrack. If this approach is used, authors should also provide a separate version of the video with the original program audio (without audio descriptions).
Multimedia in E-Books
Flash is an animation technology from Adobe Systems, Inc.. Multimedia presentations authored in Flash can contain large amounts of information yet still remain reasonable in data size, making them easy to download and play. Since Flash uses vector-based graphics, presentations can also be resized without loss of clarity-a boon to users with visual impairments.
A recent development in Flash technology is the ability to include native Flash captions within the presentation itself. NCAM developed CC For Flash, a Flash component that allows Flash developers to easily incorporate closed captions within Flash movies. It supports closed caption files which can be created using MAGpie, and can be used on all types of Flash movies, including Flash video (using external caption files or internal cuepoints), sound objects, and native timelines. Developers can set various text attributes, including font face, font size, foreground color, text box size, opacity and background color. Versions of CC For Flash are available for Actionscript 2 and 3 projects. For those situations where Flash programming is not possible, ccplayer is also available. ccPlayer is a completely accessible, precompiled Flash movie player which allows a web master to easily embed a caption-enabled media player directly in a web page.