Videotelephones are devices that transmit and receive video images as well as sound. This category includes standalone dedicated products as well as systems based on personal computers. Standalone systems have a camera, a video processor, a video encoder and decoder (codec), and a screen. These units are relatively expensive and may be built into the audio-visual equipment of a conference room; smaller units roll about on a cart. Computer-based videotelephones add a camera and microphone to the computer hardware and use the computer’s processor and data transmission equipment (modem or other).
In either case the videotelephone hardware digitizes the video and audio, transmits it over the telecommunications line, and displays the video and audio received from the other end. One advantage of the dedicated standalone systems is that they are generally easier to set up, since they do not require hardware or software installations. They may be easier to operate and more reliable as well. Additionally, most of them use direct calls over whatever facilities they have. This means that they “own” a standard or high-speed circuit; their performance is thus not degraded by network congestion. Computer-based videotelephones are much less expensive, even including the original cost of the computer, but may not perform as well in ease of use and reliability. Since they usually use the Internet, they are subject to congestion and the corresponding choppy video and audio.
The telecommunications facilities used for videotelephony range from standard analog lines to multiple ISDN and high-speed digital lines. The higher the available bandwidth, the more information that can be sent and received. This translates into several characteristics that affect the accessibility of the medium. Higher bandwidth means:
In addition to audio and video, many videotelephone systems permit the transmission of a text stream in both directions. This allows for both real-time captioning (if a captioner is provided and connected properly) and a text dialogue when needed. This text capability is not compatible with TTYs.
Videotelephony is covered by a number of International Telecommunications Union (ITU) standards that allow different products to communicate together. Some of these cover video and audio coding for analog, ISDN, and Internet videotelephony. Some cover interoperability between high-speed multimedia and low-speed single medium equipment. Some cover text transmission as part of a multimedia stream. Taken together, these standards establish a base upon which videotelephony can address the needs of users with disabilities.
It is important to understand that a technical capability does not automatically make a particular service accessible. For example, the ability to have a text box on a videotelephone screen does not fill that text box with a transcript of what is being said on the audio track. Whoever is producing the content or moderating the call must make arrangements for the text information to be provided.
Videotelephony has three main modes:
Videotelephony devices and services are capable of sending and receiving sign language, and for use in speech reading. The problem is quality, which is dependent on the equipment and the data capacity of the lines used. Both the video and audio signals are digitized and compressed; this requires significant computing power (as does the task of converting the compressed digital content back into images and sounds on the receiving end). The lines carrying the content must be capable of carrying it sufficiently fast, without loss. Dedicated lines or circuit connections can use their full bandwidth for the application. Their performance is better than that of a shared resource such as the Internet. Internet traffic can cause delays and loss of data, resulting in incomprehensible sign language on the receiving side. The key concepts are image size and frame rate. As each increases, both the computing power and the transmission speed requirements also increase.
Video Relay Service (VRS) is an extension to TRS that allows users to communicate point-to-point with a sign language interpreter over a videotelephone link. The interpreter then communicates with the hearing person over a regular phone line. VRS lets sign language users communicate more naturally. It has not been mandated by the FCC in the latest proposed TRS Rules. It is in place in only a few states. Users cannot call in from their own videotelephones, but must use a limited number of public stations.
Remote video interpreting (RVI) is a videotelephone-based sign language interpreting service. It may be point-to-point, with only the sign language user and the interpreter connected by video, while the sign language user is at a conference or class. Or it may be multipoint, with the sign language user and the interpreter connected to a videoconference. In either case the interpreter and the sign language user do not need to be at the same place.
Videotelephony and still-picture telephony have both been found beneficial
and useful to people with cognitive disabilities (Francik et al, 1999).
1193.41(c) Operable with little or no color perception.
1193.41(d) Operable without hearing.
1193.41(h) Operable without speech.
1193.43(a) Availability of visual information. Note: product provides this capability, but the appropriate content must be actively transmitted by the other party.
1193.43(b) Availability of visual information for low vision users. Note: product provides this capability, but the appropriate content must be actively transmitted by the other party.
1193.43(c) Access to moving text. Note: product provides this capability, but the appropriate content must be actively transmitted by the other party.
1193.43(d) Availability of auditory information. Note: product provides this capability, but the appropriate content must be actively transmitted by the other party.
1193.43(e) Availability of auditory information for people who are hard of hearing. [Audio output can be set to a high level.]
1193.43(f) Prevention of visually-induced seizures.
1193.43(g) Availability of audio cutoff.
1193.51(b) Connection for external audio. [Audio output can be connected to assistive listening devices.]