HDTV High Definition Television Terminology

Okay, I admit that I am addicted to my home theater. My wife and I both enjoy watching movies on Friday night and it has become a bit of a family tradition. I also think that exciting things are happening with the new high definition television (HDTV) products that are hitting the market. Prices have steadily dropped over the past few years and I think they will stabilize in 2007, so it is time to start to understand the new lingo that goes with new technology.

What do the i and p mean in the resolution standards
This is one of the most common questions. ‘i’ simply means interlaced. A television display is made up of lines of dots. Each line of dots is projected on the screen one at a time in rapid succession. Interlaced means that alternate lines are projected, which means odd numbered lines first and even numbered lines second. It takes two full passes to display an image frame on the screen, but this happens so fast that you do not notice it. ‘p’ means progressive scan. With a progressive scan, all the lines are projected in successive order, which means line1, line 2, line 3, etc., in a single sweep down the display. Moving images tend to be clearer and movement smoother with a progressive scan. Interlaced displays make two passes with image information captured at slightly different times, which sometimes makes the image look slightly jagged and movement looks slightly grainy.

What do the numbers mean in the resolution standards?
With high definition resolution standards, the 720 or 1080 simply means the number of horizontal scan lines that make up an image. 1080i uses 1080 horizontal lines that are projected in an interlaced pattern. 1080p uses 1080 horizontal lines projected using progressive scan. From a technical perspective, a minimum of 720 scan lines is required for high definition television.

Aspect Ratio This is a proportional designation for the width of a display relative to the height. Most high definition movies are best viewed in wide-screen mode, so you should look for a display with an aspect ration of 16:9 to take advantage of this. Some HDTVs have an aspect ratio of 15:9. Most standard televisions have an aspect ratio of 4:3. Once again, go for the 16:9 aspect ratio.

CableCard A CableCard can be used in newer Digital cable ready (DCR) HD televisions. A CableCard is provided by your cable company. The card plugs into a special CableCard slot in the high definition television. This eliminates the need for a cable box. You may still need a cable box for pay-per-view and interactive viewing features. Check with your cable company to see which features they offer with a CableCard. If you do not use some of the special features, you may be able to eliminate the need for the cable box.

Digital Television Resolutions Here is the current line-up for resolution option for digital television.

• 480p 480 horizontal scan lines that are interlaced. The typical standard used by EDTV. It does not meet the standards for high definition, but is an improvement over standard television.
• 720p 720 horizontal scan lines using progressive scan. If you cannot afford the higher-end 1080 scan line models, this is the next best thing. It does look great on small screens.
• 1080i Just one notch down from the top, 1080i produces 1080 horitontal interfaced scan lines. Regardless of which high-end HD technology you buy, most cable companies are only capable of transmitting using 1080i or 720p. 1080p televisions default to 1080i or 720p mode if a full 1080p signal cannot be achieved.
• 1080p1080 horizontal scan lines using progressive scan technology. The current gold standard and high end resolution that is theoretically capable of producing the very best viewing quality in high definition television. Right now, it doesn’t get any better than this, so if you can afford it, check it out. Be aware that most cable companies are not yet capable of transmitting 1080p signals, so your favorite sport will probably be displayed using a different standard.

EDTV This means Enhanced Definition Television. While it is digital, it is not HDTV and does not meet the requirements for the high definition standard. The picture quality is usually much better than standard television, but it is not as good as HDTV. EDTVs typically display 480p signals and can convert HD signals to this standard.

Front Projectors For the real movie theater experience, nothing beats a good front projector installation. This approach uses a high definition projector to display movies on a projection screen. The projector can be ceiling mounted, floor mounted or mounted on a rear wall if the room is small enough. Projectors can display movies on very large wall-sized screens, which makes this method most akin to a real movie theater experience. These installations can get to be very expensive and are typically used in high-end homes where a room is dedicated as a home theater. There are two projection technologies commonly found in front projectors: LCD and DLP. LCD uses light projected through a transparent LCD filter that uses colored pixels to create images. DLP (Digital Light Processing) is a technology developed by Texas Instruments that uses mirror pixels to create a reflected image. DLP projectors tend to produce deeper blacks, which enhance colors and therefore tend to look much better. Some DLP projectors do exhibit a problem called "the rainbow effect" where there is a visible flash of color with bright objects on dark backgrounds. More expensive models may use multiple chips to produce individual red, green and blue, which tends to reduce or eliminate the problem. Front projector systems may require an almost totally darkened room–much like a movie theater–for the best movie experience.

HDMI Input This is a new interface standard for high definition televisions. HDMI stands for High Definition Multimedia Interface. If you are looking for an high definition television, it should have at least one of these connectors. If you want to connect multiple HD devices, such as a cable box and a high definition DVD player, look for a television with multiple HDMI connections. Switching boxes are also available, but right now they tend to be pricey. HDMI cables are also a bit pricey and can run $60 for a six-foot cable. If your high definition devices do not come with a cable, see if you can get the sales person to toss it in to close the deal.

Static versus Dynamic Contrast Ratio In simple terms, the contrast ratio is the difference between the whitest white and the darkest black. Many televisions do not produce a black color (no illumination) on a screen, but rather produce a gray color. A darker black makes the colors stand out much better and the picture therefore looks brighter.

The contrast ratios touted in the specs are mostly “smoke and mirrors” because there are multiple methods for measuring contrast ratios and no one standard is being used. You have to view a television in a showroom lighting conditions that are similar to the room in your home where you spend the most time watching television. Focus on the black areas of a video and you will understand what to look for with contrast ratios.

Plasma screens inherently have better contrast ratios and brighter colors than LCD screens, but LCDs are catching up. Plasma screen look better than LCDs in a very dark room, while LCDs typically look better than plasma in a moderate to well-lit room. The only factor that is really important with contrast ratio is how the video image looks to you. Make sure that you have the showroom sales rep turn the room lights up or down to match the lighting in your home theater.

HDTV Monitor This is a high definition display without a tuner. They are sometimes called "HD Ready" television. If you are using a high definition cable or satellite signal for your high definition viewing, you do not need a tuner. Your cable or satellite box will decode the signal. A tuner is only necessary if you will be receiving your television signals via antenna.

LCD Televisions LCD stands for Liquid Crystal Display. It is the same technology used in LCD computer monitors. LCD televisions are slimmer, lighter and brighter than plasma displays. They may be a better choice under normal lighting conditions. LCDs do tend to suffer from viewing angle problems, which means that colors and images tend to be best when viewed perpendicular to the screen. The viewing angle issue is getting to be less of a problem with newer models, but be sure to check this out when you visit a showroom. If you tend to invite 10 friends over to watch football, it can be a bit difficult to cram them all directly in from of the screen.

Plasma Televisions Plasma display televisions can produce spectacular images, particularly in darker room settings. They have a much wider viewing angle than LCD televisions. Plasma images are crisp, with bright colors and very good contrast. Plasma televisions tend to be heavier and run warmer than LCD televisions and many do have a problem with screen burn-in. Burn-in produces a residual ghost image if a pattern, such as a logo, is displayed on the screen for long periods of time. Most of the time, this image will fade over time when movies are displayed, but a few sets have had problems with permanent burn-in. I’ve also been told that plasma displays do not work above 3,000 feet in altitude, but I have not been able to verify this.

Rear Projection Televisions Rear projection televisions offer a real bargain in high definition viewing. Although they are much bulkier than LCD or plasma displays, rear projection televisions are priced substantially less than HD televisions using those technologies. Like some LCDs, rear projection televisions do tend to exhibit problems with viewing angles, so check this out in the showroom. Also, there is a lamp in these models that can cost $200 to $500 to replace. keep this in mind because you may have to replace it some time over the life of the television.

So… which features do I want in a high definition television?
In a nutshell, go for the largest screen you can afford. Test it in the showroom while sitting at approximately the same distance as you would at home. Check the viewing angle. If it’s just you and a significant other, most HD televisions will have a good viewing angle. If you expect to entertain a crowd, give consideration to people who may be sitting on the fringe areas.

Don’t expect 1080p resolution from your cable or satellite service provider for some time. 1080p is currently great for Blu-ray movies and is an investment in 1080p reception for the future.

Don’t consider anything other than a 16:9 aspect ratio.

Try to simulate your expected room lighting while in the showroom. Some showrooms have dimmers on their room lighting so that you can do this. LCDs may look better in normal room lighting, plasma displays may look better in darker rooms, while front projectors may require an almost totally darkened room.

Other References:
CNet HDTV World

The Relationship Between HDTV Refresh Rate and Frame Rate