The original HDTV technology offers vertical resolution that ranges from 720 lines withprogressive scanning (720p) to 1080 lines with interlaced scanning (1080i). Full HDTV provides 1080 lines with progressive scanning (sometimes referred to as 1080p). In these specifications, the numeral indicates the number of horizontal lines in the complete raster, the p stands for progressive scanning (where each scan displays every line in the imageraster sequentially from top to bottom), and the i stands for interlaced scanning (where each scan displays alternate lines in the image raster, and two complete scans are therefore required to display the entire image).
Progressive scanning is considered superior to interlaced scanning for full-motion video displays, because there is less jitter, particularly for the portrayal of objects that move diagonally or vertically across the screen. The improvement is especially noticeable for fast-moving images, typical of television and DVD programs. Another advantage of progressive scanning is the fact that it is required for satisfactory video on TV sets that use micro displays, plasma displays, or liquid-crystal display (LCD) flat panels, all of which are becoming increasingly popular. The improved image quality afforded by full HDTV is well suited to the extra-large-screen displays used in home theater systems.