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Introduction
Short for high-definition television, HDTV
is a digital television format, with the combination of high-resolution video
and theater like sound to create a movie theater quality TV viewing experience.
The original schemes were analog, but HDTV almost exclusively refers to
various digital audio and video technologies and standards.
Features of HDTV
HDTV is approximately twice the vertical and
horizontal picture resolution of today's NTSC TV, which in effect makes the
picture twice as sharp. HDTV also has a screen ratio of 16:9 as opposed to
most of today's TV screens, which have a screen ratio of 4:3. HDTV offers
reduced motion artifacts (ie ghosting, dot crawl), and offers
5.1 independent channels of CD-quality stereo surround sound.
Regular NTSC signals have 525 lines of resolution.
HDTV has 1125 lines of resolution having over five times the video information
than that of a conventional NTSC-type TV set. In spite of its obvious
advantages, transmission requires extraordinary bandwidth of five times the
capacity of a conventional TV signal.
HDTV also come with the following
minimum performance attributes: a receiver that receives ATSC terrestrial
digital transmissions and decodes all ATSC Table 3 video formats; a display
scanning format with active vertical scanning lines of 720 progressive (720p),
1080 interlaced (1080i), or higher. Following are the formats used in HDTV:
480i - 640 x 480 pixels interlaced · 480p - 640 x 480 pixels progressive · 720p
- 640 x 480 pixels progressive · 1080p - 1920 x 1080 pixels progressive
Types of HDTV Displays
There are four major types or High Definition
televisions in the market,
Direct-view TV
A direct-view television is the type we are all familiar with. Direct view
televisions are based on CRT (Cathode Ray tube technology), a scanning
electronic gun to "paint" an image on a phosphor coated screen. Direct-view
televisions are now available in analog, digital and HDTV versions. The later
models are often over 28" size with the largest hovering at 40". CRTs are
popular for near total blacks and wide contrast range that produces the
creamiest of pictures that pleases most eye. Recent breakthroughs include
shallow tubes.
Flat Panel
This is the newest type of high tech television. Flat panels fall into two
categories: LCD and Plasma. Flat panels are generally slim (only a few inches
deep) and very attractive. LCD's are commonly much smaller than plasma's and
make great sets for kitchens or rooms where space is at a premium
Rear Screen TV
Rear projection televisions (RPTV) generally use analog CRT's but more
recently consumer electronics companies have introduced digital rear
projection televisions. These digital rear projectors employ LCD, DLP or LCosS
based technology. The screen size for rear projection televisions typically
range from 40 to 70 inches. CRT based sets tend to be much cheaper than the
newer technologies but are usually much bulkier and heavier. Rear screen TVs
offer high resolution and bright colors, and newer models use high-quality
screens that allow for many viewing angles.
Front Screen Projection TV
Generally used in larger rooms like home theaters, and are great for
replicating the movie theatre experience. Front projectors are available
in variety of technologies as listed above (CRT, LCD, DLP, LCOS) that exhibit
advantages of each in the picture image characteristics and resolutions
capability.
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