High-definition television (HDTV)

Are you too mystified and intrigued by this new kid on the TV block: high-definition television (HDTV). Expectations run high, but so is the uncertainty - what is really different about it, when compared with standard-definition television (SDTV)?

In simplest terms, while both use digital signal, HDTV uses more pixels (pix-el/ement, physical display unit of image-forming television screen) per given screen area than standard digital television. This results in finer resolution, as well as smoother motion and better color definition. This is especially advantageous with larger TV screen formats, which with standard pixel number have them enlarged enough to cause picture granulation. Due to smaller pixel size, high-definition TV screen has 2-5 better resolution than standard TV.

Compared to the standard (analog) TV, standard digital TV (SDTV) has the same 720x480 pixels resolution, but has the advantage of progressive (continuous) scanning (denoted 480p), as opposed to inferior alternate line scanning (480i, for "interlaced" scanning) of the analog TV. But even more, digital TV owes its quality to the properties of a digital TV signal, which is code based (binary code, 0,1), thus much less affected by the amplitude loss in transmission. Unlike it, analog TV signal is flow based, and needs to be re-enforced in transmission by a number of amplifiers, creating electronic noise and distortions.

Digital TV signal also can be compressed much more efficiently, allowing for significantly higher channel capacity.

 For TV screens smaller than 27" DTV is as good as HDTV. Larger screens, however, benefit from higher density resulting in smaller pixel size.

High-definition television begins with 1 million pixel level, or 1280x720 pixel screen (also progressive scanning, thus 720p format). The next larger format is 1920x1080, which comes either as 1080i (with interlaced scanning), or 1080p (progressive scanning) format. There are intermediate formats, such as one used in Australia, which is termed HDTV there, and "enhanced digital TV" elsewhere.

While interlaced scanning has the advantage of using only half the bandwidth required by progressive scanning, allowing it to achieve higher resolution than progressive scanning for given bandwidth (due to a higher pixel count possible), its alternate line refreshing mode produces undesirable artifacts and effects, tending to cause eye strain and fatigue. Due to this disadvantage, it was quickly abandoned by the PC industry, and will likely be eclipsed by progressive scanning in the area of HDTV as well.

HDTV comes with wider screen format. Its 16:9 screen ratio is between the nearly square 4:3 ratio of standard television, but not as wide as format used for most movies (from 5:3 to 3:1 screen ratio). It will still some cause cropping, and display black top/bottom bars when playing such movies, although less than standard television. On the other hand, HDTV format will show vertical side bars with some older TV shows and movies.

Although not inherently part of HDTV, it comes with top-notch audio quality (Dolby Digital), superior to standard TV audio. Also, being using digital technology, HDTV offers steady quality and higher reliability.

So, what do you need to be able to watch HDTV? Other than high-definition TV set with high-definition screen and built-in or set-top HD tuner for HD signal processing, you need - of course - HDTV signal itself. This signal can be received either by a standard UHF antenna (for local HDTV broadcasts not transmitted through cable or satellite TV), TV cable (for HDTV from cable TV service) or HDTV-capable satellite TV dish.

While non-HDTV set still can receive HDTV channels, if hooked up with HDTV decoder, you will only have a partially improved picture quality. And vice versa, HD TV set often has standard (analog) signal picture showing worse than on standard TV sets. Part of it is that HDTV sets generally have larger screens, magnifying picture defects, which are rather numerous in the analog mode. Adding to that, the superior screen resolution of an HD television set will often show such defects more clearly than lower resolution standard TV screens.

Nothing is perfect, and that includes HDTV. But if you want large screen television, HDTV is the way to go. Available HD programming is booming, and some technical problems still plaguing the execution will likely be soon remedied. If you are for HDTV, the time is on your side.  þ

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