high-definition television (HDTV)

Any system producing significantly greater picture resolution than that of the ordinary 525-line (625-line in Europe) television screen. Conventional television transmits signals in analog form. Digital HDTV systems, by contrast, transmit pictures and sounds in the form of digital data. These numerical data are broadcast using the same high radio frequencies that carry analog waves, and computer processors in the digital television set then decode the data. Digital HDTV can provide sharper, clearer pictures and sound with very little interference or other imperfections. Of perhaps greater importance, digital television sets will potentially be able to send, store, and manipulate images as well as receive them, thereby merging the functions of the television set and the computer.

HDTV

(High Definition TV) A set of digital television (DTV) standards that offer the highest resolution and sharpest picture. Although some HDTV sets are available in standard (rather square) screen sizes, the overwhelming majority of sets are wide screen, which eliminates most or all of the letterbox effect when watching movies delivered in their original wide format (see image below). See HDTV display modes and high-def DVD formats.

HDTV Vs. HD
"HDTV" may refer to the format or to a TV set that supports it; however, "HD" refers only to the format. To review the different types of TV sets on the market, see CRT, flat panel TV, rear-projection TV and front-projection TV.

720p, 1080i and 1080p
There are three HDTV resolutions. The first HDTV sets supported the 720p or 1080i HD format. By 2006, sets began to support 1080p. The number is the lines of resolution, and the "i" and "p" stand for interlaced or progressive scan, the latter being the sharpest (see interlace).

Convert Up and Down
Using sophisticated algorithms to fill in the missing lines, HDTV sets upconvert DVD, cable and satellite broadcasts from 480i or 480p to 720p, 1080i or 1080p, whichever HD resolution the TV supports. HD programs are broadcast in 720p or 1080i, and 720p HDTV sets downconvert 1080i broadcasts to 720p. Following are the HDTV standards (see DTV for all digital standards).

In addition, HDTV sets provide numerous zoom and stretch modes to accommodate standard TV formats, which will exist in the form of videos and DVDs for years to come (see HDTV display modes).

        p = progressive scan (non-interlaced)
        i = interlaced
                            Frame
      Resolution    Aspect  Rate    Pixel
      Horiz x Vert  Ratio   (fps)   Shape

  HD - High Definition TV (HDTV)
   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    30p     Square
   6. 1280 x  720   16:9    60p**   Square

 ** = most popular formats

HD Ready or Built In
An "HD Ready" or "HD Capable" TV set means 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" means there is a built-in HD tuner for capturing HD broadcasts over the air.

Been Around a While
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 very 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 HD formats in both analog and digital were used for creating higher-quality video than regular TV (NTSC). HD was used to shoot closed circuit presentations in corporate theaters and board rooms, trade shows and similar events. See interlace, deinterlace, DTV, letterbox, HD-DVD and aspect ratio.

Wide Screen HDTV

When a movie is displayed without modification on a standard 4:3 TV screen, the black bars at the top and bottom take up the unused space (the "letterbox" effect). Wide screen HDTVs with a 16:9 aspect ratio show wide screen movies without black bars entirely or with much thinner black bars (see HDTV display modes). (Image courtesy of Intergraph Computer Systems.)

HDTV

(communications)

high-definition television

HDTV - High Definition Television