Figure 17.1 Example of finger spelling
Courtesy of Omnitor ABThe example in Figure 17.1 is interesting for designers, since it conveys a
sense of the size and quality of the video images, and also the frame rate, as
will be discussed here.
The frame rate is measured in frames per second (fps).
The most common video resolutions are:
■■ Common Interchange Format (CIF)—325 ×288 pixels
■■ Quarter CIF (QCIF)—176 ×144 pixels
■■ Sub QCIF (SQCIF)—112 ×96 pixels.The video quality required for sign language is shown in Figure 17.2
expressed as usability (that is, as a function of the temporal resolution or fps,
and the image resolution).
Text over IP has its own requirements, which will be discussed next.Text over IP (ToIP)
Although instant messaging (IM) is considered an interactive text communi-
cation capability, it does not meet the needs of the hearing and speech disabled
users:
■■ IM is used with times of seconds to minutes between messages. The
Message Composition Indicator, such as “is typing” indicator (see
Chapter 13) tells the other party to wait.290 Chapter 17