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What are digital home theaters? Is your home theater really digital? Even if it says it is, it might not be! Read on to find out why....
When you look at a TV screen or the screen on your computer you are looking at images that are made up of pixels. The images you see are little tiny blue, green and red dots that are grouped together and the term “pixels” is short for picture elements.
Lets start at the beginning with analog TV’s to see how far we’ve come in the evolution of digital home theaters… The images you see on your TV screen are those groups of pixels that change 30 times every second….but only if you sit far enough away does that appear as a smooth and coherent image. This process is known as Persistence Of Vision. Digital Home Theaters – Scanning Lines… Unlike digital home
theaters, your old analog TV viewing is based on 525 horizontal scanning lines
but only 480 lines are actually used to scan the image from top to bottom. What
you are seeing is actually an image composed of 60 still pictures that happen so
quickly that we see it as a continuous image. This system is called 480i (‘i’ for interlaced) because it is composed of 480 interlaced lines and is known as the standard definition with digital TV. A DVD image represents standard definition. All HDTV pictures are digital but not all digital TV is high definition so just because a TV is “digital” does NOT mean it is HDTV. The North American Digital TV standard was established in 1995 by the ATSC (Advanced Television Systems Committee and has 18 formats with different levels of clarity. They are: Standard Definition (SD), Enhanced Definition (EDTV) and High Definition (HDTV). A digital TV while playing a DVD’s 480 line image can be progressively scanned one line after the other rather than interlaced. This is 480p and is Enhanced Definition TV (EDTV). Almost all newer DVD players, even cheap ones, can do both interlaced and progressive scan signals. 480p (‘p’ for progressive) TV images have a smoother film like look to them. Digital Home Theaters – Square or Wide Screens… Digital home theater images can be viewed in the almost square format (4:3) or widescreen (16:9). Those numbers are based on the ratio of the width to the height of the TV screen. Most new TV’s have the rectangular shape of the widescreen (16:9) screen and it is now the standard for digital TV. The reason is because its close to the shape of the screen that most movies have been made in since the 1950’s when Panavision and Cinemascope appeared. Some new HDTV ready TV sets are still offered in the square screen version but eventually all will be the widescreen format because that is where all the programming is going. Digital Home Theaters – More Detail For Your TV Image… More scanning lines from top to bottom, whether they are progressive or interlaced means more detail in your TV picture. Some of the U.S. networks are now broadcasting in HDTV with up to 720p (ABC) or 1080i (NBC & CBS), but many digital home theater TV’s are not capable of displaying full 720p or 1080i signals. These TV’s will “scale” down the signal to 480p. This is way better than analog TV but nowhere near as good as the image you will get with a digital TV that can display the signal of HD 720p or 1080i. Its not just vertical detail with the scanning lines because there is also horizontal detail in a TV image. The number of pixels or dots across the screen will determine the horizontal detail of both standard or high def signals. Standard definition may have 704 pixels across the screen. A 1080i HDTV picture image can have 1920 pixels but the 720p. Both 1080i and 720p can offer images up to five times clearer than your analog TV but 720p will produce a better image for fast motion viewing like sports. The 1080i would be a little better for images that have little motion. Either way, you will be able to see amazing details that you could never see before on your analog TV….even details like scratches on a desk or individual blades of grass. To put it in perspective, your old VHS video’s are only able to put out 240 lines of resolution, which is why they always look out of focus. Make no mistake, HDTV is as big a leap in TV as the switch from black and white broadcasting to color! You will find that you can sit closer to a digital TV with a digital signal because the image will be so clear. A rule of thumb for the viewing distance for digital home theaters is to double the diagonal screen size for HDTV or DVD’s on a High Definition set and triple the diagonal screen size when viewing non-HD signals. With digital TV’s you will also see an absence of “graininess” that you see with analog TV’s. That’s why DVD’s can look amazing even on old analog TV’s. The only downside to a digital TV is that your image might freeze or pixelate once in awhile from a weak digital signal or physical damage to the surface of the DVD. Digital Home Theaters – What About The Sound? Dolby Digital is the standard for all SD, ED and HDTV programming. That means it is a digital audio signal of at least 2 channels and in many cases, 6 (Dolby Digital 5.1 surround). Upgrading your TV to a digital one is a good start but for the entire experience you will need to upgrade to digital audio because only then will you get the full digital home theater experience. Digital Home Theaters - Receiving An HDTV Signal... So how do you receive HDTV broadcasts? The 3 most common methods are via cable, satellite and terrestrial reception from a digital HDTV broadcast station. If you want to pick up terrestrial digital broadcasts then you will need an outboard HDTV tuner or an integrated HDTV set that has its own digital HDTV tuner because most HDTV and EDTV sets are merely monitors and don’t have an internal HDTV tuner for reception by antenna. If you go with satellite TV or cable, and I think satellite TV is better, then you won’t need that extra HDTV tuner because your satellite or cable receiver will do that for you. You need to specify an HDTV ready satellite or cable box though. Digital Home Theaters – How Long Do I Have To Change Over To A Digital TV? As quickly as people replaced their VCR’s with DVD players, they are doing the same in moving towards High Definition ready large screen TV sets and projectors. Large screen rear projection TV’s and direct view High Definition ready TV sets and flat panel displays are the fastest growing segment of sales at electronics stores. The transition to full digital HDTV throughout North America probably won’t be done until 2010 so you still have time to decide on what you want to do with your digital home theaters as far as the type of TV you want.
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