riginally, the NTSC decided that the best way to fit a 525-line video signal into a 6MHz broadcast channel was to break each video frame into two fields, each holding half of the picture. Interlacing is a technique cameras use to take two snapshots of a scene within a frame time. During the first scan, the camera creates one field of video, contain- ing even-numbered lines, and during the second, it creates another, containing the odd- numbered lines. The fields are transmitted sequentially, and the receiver reassembles them. This technique makes for reduced flicker and therefore greater brightness on the TV receiver for the given frame rate (and bandwidth). Interlacing is rough on small text, but moving images look fine. Progressive, or noninterlaced, scanning is a method for displaying, storing, or trans- mitting moving images in which the lines of each frame are drawn in sequence. This type of scanning is used in most computer monitors. There are a number of advantages asso- ciated with progressive scanning, such as a subjective perception of an increased vertical resolution. With interlaced images, the perceived vertical resolution is usually equivalent to 60% of the active lines. This is why HDTV standards such as 1080i (1,920 X 1,080, interlaced) are generally perceived as a poorer quality than 720p (1,280 X 720, progres- sive). Additional benefits include the absence of flickering of narrow horizontal patterns, easier compression, and simpler video-processing equipment. The ATSC high-definition standard includes three basic formats: HDTV, EDTV, and SDTV. EDTV is largely a marketing term, referring to low-resolution TVs with minor enhancements. Digital TVs often have a 16:9 widescreen format and can dis- play progressive-scan content. Each of these formats is defined by the number of lines per video frame, the number of pixels per line, the aspect ratio, the frame rep- etition rate, and the frame structure (i.e., interlaced scan or progressive scan). The ATSC standard recommends that the receiver seamlessly