 system information that a switch can use to assess network device capabilities, and are hot-swappable. Group of Blocks. The ITU-T's H.261 Recommendation process divides a video frame into a group of blocks (GOB). At CIF resolutions there are 12 such blocks and at QCIF there are three. A GOB is made up of 12 macroblocks (MB) that contain luminance and chrominance information for 8448 pixels. A GOB relates to 176 pixels by 48 lines of Y and the spatially-corresponding 88 pixels by 24 lines of CB and CR. Each GOB is divided in 33 macroblocks, in which the macroblocks are arranged in three rows that each contain 11 macroblocks. A codec manufacturer. GEC and Plessy combined their efforts to create an early video codec that depended on BT's compression algorithm. GPT codecs are prevalent in Europe. Grand Alliance The merger of four competitive HDTV systems, previously proposed to the FCC as individual standards, into a collaborative venture that is backed by all the supporters of the original four separate Glossary of Terms systems. The companies that comprise the Grand Alliance include AT&T, the David Sarnoff Research Center, General Instrument, MIT, North American Philips, Thomson Consumer Electronics, and Zenith Electronics. The new HDTV standard was approved in late 1996 after a compromise between the computer and broadcasting industries was reached. graphical user interface (GUI). A "point and click" computing environment that depends on a pointing device such as a mouse to evoke commands and move around a screen as opposed to a standard computer keyboard. graphics Artwork, captions, lettering, and photos used in programs, or the presentation of data of this nature, in a video communications system. graphics accelerator A video adapter with a special processor that can enhance performance levels during graphical transformations. A CPU can often become bogged down during an activity of this type. The accelerator allows the CPU to execute other commands while it takes care of the compute-intensive graphics processi