Glossary of HDTV Terms
If you’re a technical communication professional writing about HDTV (High Definition TV) you should know the meaning of the following industry terms:
Aspect Ratio
The ratio of a TV screen’s width to it’s height. An HDTV screen is much wider than a traditional cathode-ray tube (CRT) screen. A typical HDTV aspect ratio is 16:9. That is, a typical HDTV screen would have 16 inches in width for every 9 inches it has in its height. If for example, it is 48 inches wide, it’s height would be 27 inches. Traditional cathode-ray tube sets have 4:3 aspect ratio. That is, a 48 inch wide traditional TV screen would be 36 inches high. Wide-screen films display much better on a HDTV set. The same film would leave black bands on the top and bottom of a traditional TV set.
CRT
Cathode-Ray Tube. The good-old fat TV monitors that operate with a cathode-ray tube shooting electrons onto a fluorescent screen to create moving images. If you have one, you can’t sell it to anybody today. It is so 20th century…
HDMI Cable
High Definition Multimedia Interface cable yields the best uncompressed video and multi-channel stereo audio quality for such consumer electronic devices as HDTV, tuners, set-top boxes, Blue Ray players, video consoles, personal computers, and similar gadgets.
HD Tuner
If you do not have satellite or cable TV service then you need to have a HD tuner in your TV set to receive your local high-definition TV channels. HD tuners are either built into the HDTV sets or are available as external add-on components.
Interlacing (i)
Interlaced HDTV image labels carry the small-cap letter “i” after their numeric designations, such as 1080i or 480i. It is an old technology for showing images in terms of ODD and EVEN lines. Instead of drawing each line one after the other (as in “progressive scanning”), first the odd lines are painted from top of the screen to the bottom, followed by a second sweep of even lines, creating “flickering”. The image “field” is created inside the picture “frame” by painting ODD and EVEN lines separately, lines which are also called FIELDS. Traditional TV sets paint 50 (PAL system) lines a second (25 odd and 25 even fields), painting 25 frames per second. It’s opposite technology is “progressive scan” which does not create any flickering.
LCD (Liquid-Crystal Display)
A flat-panel TV technology that displays images by using liquid crystals to illuminate red, blue and green pixels. LCD is recommended especially if your TV set will display unchanging images for a long period of time, like a company logo. LCD screens can display sharp colors and text by using the anti-aliasing technology. One disadvantage of the LCD screens is that, compared to CRT and Plasma monitors, LCD is not that good in displaying deep blacks and rich grays. LCDs also have a longer “response time” than Plasma screens when rendering fast moving objects. Some LCDs also have a narrow viewing angle and “glare out” part of the images when viewed from an off-center position.
Plasma
A Plasma screen works with tiny tubes of noble gases illuminating the image and creating deep rich blacks and bright colors. However, when a static image is left for too long on a Plasma screen it can burn it and create a permanent image “ghost”. Plasma screens also do have a wider viewing angles compared to LCD screens. Plasma screens create high-contrast images in TV screens as large as 150 inches diagonally. Plasma screens are usually very thin and can be mounted on the wall like a picture frame. They do not have the kind of “motion blur” that some LCD screens have. One drawback is its high energy consumption.
Progressive Scan
An image display technology which paints a picture on screen by scanning lines consecutively, from top of the screen to the bottom. In contrast to”interlacing,” this technology, which is also referred to as “full framing,”does not create any flickering and results in sharper images. The only disadvantage of Progressive Scan is its need for higher bandwidth than Interlaced signals.
RPTV
Rear-Projection TV sets project the image from behind to a large screen upfront. It does not create images as sharp as LCD or Plasma but it is much cheaper and works well for watching sports or other events in a large room with many people. It comes in three different varieties of projection: CRT projection, LCD projection, and DLP (Digital Light Processing) projector. Although it used to be available only in bulky packages, some of the late models are light and thin enough to be mounted on the wall.
