==Phrack Inc.== Volume One, Issue Nine, Phile #8 of 10 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- "Introduction to Videoconferencing" by Knight Lightning Written On 10/3/86 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Hi, KL here welcoming you to a look at Videoconferencing. This is a relatively new field that definitely bears investigation as videoconferencing is only a step away from everyone having video communication in the home. Well enough is enough, I hope you enjoy the file --KL. ______________________________________________________________________________ Despite the growing use of videoconferencing, confusion still exists regarding what it can and cannot do. This file should begin to help answer some of the questions about videoconferencing and perhaps formulate new ideas as well. Videoconferencing is not just one thing. It takes several different forms and can be designed in many different ways. Most of these ways are probably still waiting to be discovered. First of all, there are two main categories of videoconferencing. There is Point-to-Point and Point-to-Multipoint. Point-to-point/Two-Way Videoconferencing ---------------------------------------- Two-way videoconferencing enables people to conduct meetings even though the participants are in separate locations. Using interactive video and audio equipment, participants in one location can see, hear, and interact with colleagues in another location. The most familiar example occurs regularly on TV. When a newscaster in Washington interviews a head of state on the opposite side of the world "live," that's point-to-point, full-motion, full-color videoconferencing. Point-to-multipoint/One-Way Videoconferencing --------------------------------------------- The one-way videoconference allows an organization to present video information to large audiences in multiple locations at the same time. One-way videoconferences are very different from two-way videoconferences in purpose and in implementation. Two-way videoconferences allow small groups in two, or possibly several, locations to interact audio-visually. In contrast, one-way videoconferences are designed to provide a one-way audio-visual presentation of information from an originating site to audiences at numerous receiving locations. The remote "audiences" are not seen by the initiators of the presentation. However, since both types of videoconferencing take place in real time, live, the audience can participate over the phone. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - There are two variations on the above listed categories of videoconferencing; Full-motion videoconferencing and freeze-frame videoconferencing. Each carries its own set of system requirements and each accomplishes quite different tasks. FULL-MOTION Videoconferencing ----------------------------- Full-motion videoconferencing is like watching television. You can see participants in another location in color and in "real time" motion. You can identify who is present (provided that they are within camera range) and who is speaking. You can see facial expressions, hand gestures, and general body language. Motion video is used primarily for images of people. Motion Transmission On Wideband Channels ---------------------------------------- There is far more information in moving pictures then in a still image. Consequently, the size of the communications channel required to transmit and receive motion is far greater than that required for a still image. Transmission of a television signal in its original analog form (as it would come from a TV camera), requires terrestrial television channels or a satellite transponder. Terrestrial television channels are not readily available for occasional corporate use; satellite transponders are available. Most systems therefore, incorporate digital compression techniques to reduce the bandwidth required for motion videoconferences. Example: An image in motion is refreshed on a television screen 30 times per second. This means that the bandwidth necessary to transmit the image is very high, usually 1.5 megabits per second (Mbps). This bandwidth is beyond the capacity of the standard telephone cable. A device called a "codec" digitizes the analog television signal and compresses it by eliminating redundant information. Currently, codecs can reduce the bandwidth to 56 kilobits per second (Kbps) and it is hoped that this bandwidth can be compressed even further. The resulting signal can be transmitted over less than full bandwidth channels. The picture is of somewhat less quality than the original analog image, but more than sufficient for most meetings. FREEZE-FRAME Videoconferencing ------------------------------ Freeze-frame videoconferencing is like a slide show. It captures still images either in color or black-and-white. Freeze-frame "stills" of people seem unnatural and can be distracting. Yet, freeze-frame video is best for still images of three-dimensional objects such as a product or a part, and for charts, drawings, graphics, and specially prepared presentation material. Freeze-Frame Transmission On Narrow Band Channels ------------------------------------------------- A freeze-frame system captures an image by stopping, or freezing any motion that might be present. The image can be transmitted via analog or digital signals over narrow channels. These channels are considerably narrower than those used for full-motion video conferencing. In its simplest form, freeze-frame video can utilize ordinary telephone line transmission. A single freeze-frame image will require at least 30 seconds to a minute or more for transmission. In some systems, the freeze-frame image is displayed line by line as it is received. This creates a vertical "waterfall" effect or a horizontal scanning effect. In other systems, the incoming lines of picture information are stored in a buffer until the completed picture can be displayed as a whole. In still other systems, an image emerges in successively better resolution as additional picture information is received. Enhancements To Freeze-Frame Video Systems ------------------------------------------ There are a number of ways to expand a freeze-frame video system's capabilities. One enhancement is telewriting. With a "pen" connected to a telewriting device, users can point out a portion of a freeze-frame video image, overlaying lines and markings in various colors that are displayed at all locations as they are drawn. Some telewriting devices include stored geometric shapes, logos, and symbols that can be transmitted as overlays to a freeze-frame image. Zoom capability enables close-up analysis of portions of a display. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Personal Computers and Desktop Videoconferencing ------------------------------------------------ Personal computers are beginning to be increasingly used with freeze-frame videoconferencing. PCs are used for control, for the creation of graphics, and for storage and retrieval of graphics material. There are signs that this evolution towards desktop videoconferencing has already begun. The MINX (Multimedia Information Network Exchange) work station, recently announced by Datapoint Corporation, combines a camera and speakerphone with a high-resolution-color video graphics display screen. The MINX can be configured with Datapoint's Vista-PC or with the IBM PC, AT, or XT, in which case the PC monitor is replaced by the MINX. A mode key on the workstation permits the user to shift between the video communications mode and the normal PC mode. Another indication of this revolution is provided by Northern Telecom (creators of DMS-100, 200, & 250), which recently added Meeting Communications Services (MCS) to its Meridian DV-1 voice/data system. This option allows up to 24 participants to conduct simultaneous audio communication and up to eight participants to view, modify, and exchange data using Meridian M4000 integrated terminals. A third and final example is the Luma phone from Luma Telecom. This device, which uses regular phone lines, combines audio with black-and-white freeze-frame video on a three-inch-diagonal screen. Strictly a telephone product, the Luma phone has no computer features and will not transmit data. For more information on the Luma phone, please see the November, 1986 issue of The Sharper Image catalog. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Videoconferencing is the way of the future and its only drawback is that of economic cost. Increased use of videoconferencing will depend a lot on the adoption of the Integrated Services Digital Network (ISDN), a standard, all-digital communications service promised by the regional Bell Operating Companies (BOCs). ISDN will offer users 144 Kbs or more which can be allocated among various communications tasks--data, voice, or video--in whatever proportion is necessary. This means that the available bandwidth could support simultaneous audio and video communication. ______________________________________________________________________________ References: ---------- "Electronic Meetings: Substitutes With Substance?," by Sam Dickey, Today's Office, July 1986. "Getting The Full Picture On Corporate Videoconferencing," by Marita Thomas, Facilities Design & Management, June 1986. "The Lid Is Off ISDN," Tomorrow's Communication Connection, April 1986. "Videoconferencing; An Alternative Solution," Corporate Informations Systems, General Electric (GE). ______________________________________________________________________________ Onto the next generation... --KL -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-