HDTV
HIGH DEFINITION TELEVISION
High Definition Television (HDTV) means broadcast of tele-vision signals with a higher resolution than traditional formats (NTSC, SECAM, PAL) allow. The HDTV screen uses a 16:9 aspect ratio. The high resolution images (1920 pixels × 1080 lines or 1280 pixels × 720 lines) allow much more detail to be shown. MPEG-2 is used as the compression code. The images are expected to be at least 6 times as sharp as standard definition television or analog television.
Japan had the earliest working HDTV system, with design efforts going back to 1979. Japan began broadcasting analog HDTV signals in the early 1990s using an interlaced resolution of 1035 lines (1035i). The Japanese MUSE system employed filtering tricks to reduce the original source signal to decrease bandwidth utilization. For example, three successive picture ele-ments on a line were actually derived from three separate scans. Whole camera pans would result in a loss of 50% of horizontal resolution.
SOURCES:
http://en.wikipedia.org/wiki/HDTV