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Guidelines: Accessible Video Applications



Categories: Must Should MAY

The "May Items" can provide added functionality for people with disabilities.

 

  1. If a video contains text, charts, graphs, or images that are important for the viewer to see and are not in the forefront of the image, provide an expanded version of the text, chart, graph, or image alongside the video using the SMIL format.If the video is small or in poor quality, it may be hard to distinguish information that is being displayed on screen. This may occur is a PowerPoint is being shown through a video camera. The best way to display such information is to obtain the images of the slides and present them next to the video in a synchronized format. This can be done using the SMIL format. For more information about SMIL, visit the link: http://www.w3.org/AudioVideo/If the slides cannot be obtained, create a new PowerPoint that contains the same information as the slides on the video. Make sure the slides are in accordance with the PowerPoint accessibility guidelines. If SMIL cannot be instituted, and the PowerPoint slides cannot be obtained, copy the information from the video and include that file along with the disclaimer, transcript, and video when distributing the video.

  2. Provide a sequence of chapters that can be accessed with a Table of Contents that is visible the entire time the video is playing.Using the SMIL format, make a Chapter Index that is present with the video file, so a user can skip from part to part within the file to a point of their choosing. The Chapter Index increases the usability of the file by letting users find a specific point of the video quickly and easily.

  3. Keep frame rate (frames per second) between 15 and 30 frames per second.The size of video files is determined, among other factors, by the frames per second of the video. Theless frames per second, the more choppy the video appears to be, thus lowering the quality, but at the same time decreasing the size of the video file. This decrease in size is beneficial if the video is put on the internet for users to download. The low frame rate also decreases the size of the file, making it more accessible to those with slower internet connections. On the other hand, a frame rate that is too high will have minimal benefits with an unnecessary high file size. Ideally, keep the frame rate between 15 and 30 frames per second to balance the size of the video with the quality of the video.

  4. Keep resolutions of video relatively small to keep file size down.The quality of a video is also determined by the resolution, or height and width in pixels. If a video is too large, it makes the video file very large, and thus inaccessible to those with slow computers or slow internet connections. If a video's resolution is too small, the picture becomes blurry and thus inaccessible to those who have vision disabilities. Both the height and the width of the video should be divisible by 16, when put into pixels, because other heights and widths cause problems for media players. A video file should be no larger than 640 by 480 if it is placed on the internet, because of the large file size.


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