HDTV creates lifelike pictures and digital sound. High resolution produces great clarity, and films maintain their original width. This makes for a stunning visual and aural experience. The basic form of TV today is analog TV. A 6 MHz signal carries information to each scan line of a TV picture. The analog TV signal in the United States has 525 scan lines; a picture resolution of about 210,000 pixels and a horizontal resolution of 500 dots for a color set. Each image is refreshed every 30th of a second. In contrast to analog TV there is a new form of television called High Definition Television (HDTV). HDTV has the highest digital television resolution and Dolby Digital surround sound. The resolution of HDTV is 720 or 1080 lines. Three main HDTV formats are 720p (1280x720 pixels progressive scanning), 1080i (1920x1080 pixels interlaced scanning), and 1080p (1920x1080 pixels progressive scanning). Each picture contains about 2 million pixels, and an aspect ratio of 16:9, which is close to ratios used in theatrical movies. Digital TV depends on a compression scheme called MPEG-2 that reduces the amount of data by about 55:1. The Federal Communications Commission has mandated that all stations be capable of broadcasting HDTV by 2006. In order for this to occur consumers have to buy new equipment, broadcasters have to switch to HDTV, cable operators have to convert equipment and set-top boxes, and lastly cities have to decide to build towers to broadcast the digital signal.
