Audio and Video
Audio and video share the same fundamental challenge as all nontext content: Some users will be unable to access the information since it’s available through only one sense: either vision or hearing. Audio can only be heard; video can only be seen. On the other hand, text is versatile because—thanks to text-to-speech technology—it can be both seen and heard. Consequently, the primary task of delivering accessible media is to provide a text equivalent for both visual and audible components.
Audio and video also present technical challenges. The technical requirements for network delivery of them are high—too high for some users. Users with slow Internet access may not be able to receive the large amount of data required for media. Furthermore, because digital media files are so large, Web video and audio are by necessity greatly compressed and require a fast computer processor to decompress and play. Older computers may not have the cycles needed to play media files, and some devices, such as PDAs and cell phones, may not support media playback. Finally, support for media formats is not built into browser software, which means users must install special software for playback. Users who cannot access media for technical reasons benefit from text equivalents.
For those who can access audio and video, playback must be accessible and consistent with user expectations. Users must be in control of media elements, making decisions about when to load media, when to play, and so on. For users who rely on keyboard access, media controls—play, pause, and volume—must be accessible from the keyboard.