HDTV stands for high definition television, a new means of broadcasting and the machines that take advantage of it. HDTV broadcasts video digitally, in contrast to the common analog formats PAL, NTSC, and SECAM. HDTVs first became available in 1998. Since then, television manufacturers have been doing as much as they can to encourage their customers to buy an HDTV for their next television.
HDTVs require an HDTV tuner to pick up high definition programming. These typically run about 150 US dollars (USD) and are compatible with any HDTV. Some HDTVs come with built-in tuners.
HDTV is defined as having 1080 active pixel lines and a screen with a length-to-height ratio of 16:9. This screen shape departs from decades of the conventional ratio of 4:3. The new ratio lends itself better to widescreen movies. HDTV resolution is about twice as high as typical CRT sets, which have 480 active pixel lines instead of 1080.
The increase in resolution is just one of the benefits of HDTV. Because the image is digital rather than analog, it tends to be much sharper on televisions of all sizes. Its image display technology is "progressive" rather than "interlaced", meaning that the entire picture is continuously shown, rather than alternating between partial picture displays as in a conventional television. Interlaced pixels and low refresh rates are responsible for the flickering effect seen in older televisions.
HDTV has been slow to catch on. The sets are still very expensive, in the neighborhood of 1000 USD. The Internet is causing people to watch TV less. There is limited high definition programming available although more and more channels support high definition. Getting the programming often requires a dedicated subscription although some programming can be received by a VHF/UHF antenna.
Digital television uses the MPEG-2 image compression standard, also used by DVDs, to minimize the data size of video for transmission. In 2006, it will be required for all new televisions to support digital signals, but not necessarily high definition signals.