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High Definition Television


(High Definition TV) HDTV is the high-resolution part of the digital TV standards (see DTV). It represented the highest resolution prior to Ultra HD (see 4K TV).

"HDTV" may refer to the format or to a TV set that supports it; however, "HD" refers only to the format. For more on TV technologies, see flat panel TV, rear-projection TV and front-projection TV.

Convert Up and Down
Using algorithms to fill in the missing lines, HDTV sets upconvert DVD, cable and satellite broadcasts to 720p, 1080i or 1080p, whichever HD resolution the TV supports. HD programs are broadcast in 720p and 1080i, and 720p HDTV sets downconvert 1080i broadcasts to 720p. In addition, HDTV sets provide numerous zoom and stretch modes to accommodate standard TV formats, which exist in the form of DVDs and old movies (see HDTV display modes). See HD formats.

 HD - HIGH DEFINITION TV (HDTV)                         FrameResolution    Aspect  Rate   Pixel   Horiz x Vert  Ratio   (fps)  Shape

 1. 1920 x 1080   16:9    24p Square
 2. 1920 x 1080   16:9    30p Square
 3. 1920 x 1080   16:9    30i   Square

 4. 1280 x  720   16:9    24p Square
 5. 1280 x  720   16:9    30pSquare
 6. 1280 x  720   16:9    60p   Square

  p = progressive scan
  i = interlaced

HD Ready, Capable, Built In or Integrated
An "HD Ready" or "HD Capable" TV set means that it can display 720 progressive lines of resolution (720p) at minimum and can scale up lower and scale down higher-resolution signals to fit the screen. HD Ready requires an HD set-top box from the cable or satellite company to receive HD programs.

"HD Built In" or "integrated HDTV" refers to a TV with a built-in HD tuner for capturing HD broadcasts over the air.

HD Has Been Around Awhile
Since the turn of the century, consumers have become familiar with high definition TV; however, HD was available years before that. Japan experimented with HD formats in the 1970s and 1980s and was the first to broadcast an 1125-line signal for expensive, large-screen TV sets in the early 1990s. Both Japan and Europe's initial HD formats were analog.

For many years in the U.S., various analog and digital HD formats were used to shoot closed circuit presentations for corporate board rooms, trade shows and similar events. See interlace, deinterlace, DTV, letterbox, HD-DVD and aspect ratio.

Less Letterbox on HDTV
When a wide-screen movie is rendered intact on earlier 4:3 TVs (left), top and bottom black bars are displayed ("letterbox" effect). However, HDTVs have a 16:9 aspect ratio that shows movies without any bars or with much thinner ones (see HDTV display modes). (Image courtesy of Intergraph Computer Systems.)