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The Advanced Television Standards Committee (ATSC) has set voluntary standards for digital television. The ATSC has created 18 commonly used digital broadcast formats for video. Standard television has a 4:3 aspect ratio — it is four units wide by three units high. HDTV has a 16:9 aspect ratio, more like a movie screen. The lowest standard resolution (SDTV) will be about the same as analog TV and will go up to 704 x 480 pixels. The highest HDTV resolution is 1920 x 1080 pixels. HDTV can display about ten times as many pixels as an analog TV set. set’s frame rate describes how many times it creates a complete picture on the screen every second and here it varies from 24p (24 frames per second, progressive) to 60p.

DTV usually uses MPEG-2 encoding, the industry standard for most DVDs, to compress the signal to a reasonable size. MPEG-2 compression reduces the size of the data by a factor of about 55:1, and it discards a lot of the visual information the human eye would not notice was missing.

However, even though a digital signal is better quality than an analog signal, it isn’t necessarily high definition. HDTV is simply the highest of all the DTV standards. But whether you see a high-definition picture and hear the accompanying Dolby Digital® sound depends on two things. First, the station has to be broadcasting a high-definition signal. Second, you have to have the right equipment to receive and view it. We’ll look at how to get an HDTV set and signal next.