t's Advanced Research Projects Agency (DARPA) and other federal customers. B-frame A mandatory MPEG picture coding technique that provides bi-directional interframe compression and which uses interpolation to predict a current frame of video data based on a past frame and a "future" frame. binary A method of coding in which there are only two possible values, 0 and 1, for a given digit. Each binary digit is called a "bit." binary large objects BLOBs. Events on a network caused by the transmission of bit-intensive images that cause bottlenecks. B-ISDN Broadband ISDN. The ITU-T is developing the B- ISDN standard, incorporating the existing ISDN switching, signaling, multiplexing and transmission Video Communication: the Whole Picture standards into a higher-speed specification that will support the need to move different types of information around the public switched network. Binary Digit. The basic signaling unit in all digital transmission systems. bit plane The memory used to represent, on a VDT, one bit per pixel. Multiple bit planes can be introduced to produce deeper color and, as the number of bit planes increase, SO does the color resolution. One bit plane yields two colors (monochrome). Two yields four colors (00, 01, 10, 11), four can describe 16 colors, and SO on. bit rate The number of bits of information transmitted over a channel in a given second. Typically expressed bps. bit-block transfer Bit-BLT. The movement of an associated group of pixels around on a screen. When a window is opened or moved around on a PC or X-terminal a Bit-BLT occurs. bitmap The total of all bit planes used to represent a graphic. Its size is measured in horizontal, vertical and depth of bits. In a one-bit (monochrome) system there is only one bit plane. As additional planes are added, color can be described. Two bit planes yield four possible values per pixel, eight yield 256, and SO on. black level The lowest luminance level that can occur in video or television transmission and which, when viewed on a monitor, appears as 