FAQs:HDTV
FAQs: High-Definition Television (HDTV)
What is HDTV?
Think of it as a movie theatre experience in your own home – with a sharper, clearer picture; wider screen; and sweet surround sound.
Regular analog television shows a maximum of 480 viewable lines of resolution. HDTVmonitors, however, display up to 1080 active, viewable lines of resolution. These extra lines give you that sharper picture with the extra crisp detail.
HDTV also can offer incredibly high color resolution as well, using a greater selection of color palettes. In addition, HDTV has the ability to provide up to five full channels of audio with deep bass effects, using Dolby Digital audio encoding…just like your favorite DVDs.
Many HDTVs also offer 16:9 wide-screen “aspect ratio” – width to height of screen – similar to that of movie theatres. This is compared to the 4:3 aspect ratio that Standard TV and some Enhanced TVs use.
What do interlaced and progressive scanning mean?
TV images are divided into horizontal lines. The sequence by which those lines are redrawn on the TV screen is called the scanning mode. Two different scanning modes – interlaced and progressive – are defined for use in HDTV systems.
Interlaced scanning means the screen shows a picture using two fields with each field redrawn every 60th of a second.One field contains all of the odd lines of the picture; the other field contains all of the even lines. Thus, the entire picture is “redrawn” every 30th of a second. All existing standard-definition TV broadcast systems use interlaced scanning. This technique works in conjunction with one of our visual traits – called “persistence of vision” – in which our brains will combine multiple images that are flashed before our eyes in quick succession into one continuous, moving stream. Our eyes are “fooled” into believing we’re viewing a single, higher-resolution picture,when in reality, we’re looking at two lower-resolution pictures that are”interlaced.” As screens get larger, tricking our eyes to use interlaced images becomes more difficult. Flickering is more obvious, and picture quality deteriorates.
Progressive scanning displays all lines at once, with a single picture “redraw” every 60th of a second. The benefits are less flicker and smoother motion on the screen, but it requires greater bandwidth from broadcasters and service providers.
A picture that is 480p (480 lines using progressive scanning) is considered to be Enhanced Definition vs. Standard TV in 480i (interlaced scanning). High-definition television uses 720p or 1080i. Most, though not all, HDTVs accept the 1080i format.Support for 720p, 480p, and 480i differ from model to model. HDTVs have “native”display formats as well. An HDTV might accept 1080i but convert it to 720p.
What’s the difference between HDTV and digital television?
HDTV is a subset of the 18 digital television (DTV) formats currently available to broadcasters and media players (like DVD players). Think of HDTV as a type of digital television (DTV) service – but one that takes TV viewing to a whole new level. More pixels on the HDTV screen means richer detail and greater overall picture clarity.
To give you some numbers to play with: Standard-definition video offers roughly 338,000 pixels of resolution. High-definition video offers roughly 920,000 pixels (for 720p mode) or 2,000,000 pixels (for 1080i mode). The improvement from standard-definition to 1080i high-definition mode, therefore, can give you about 6 times more picture information – approximately 2,000,000 pixels divided by 338,000 pixels.
