A/V Systems Specialists

High Definition TV     High Definition TV (HDTV) is the clearest form of Digital TV (DTV). The TV picture that we have been seeing for years is analog (made from varying signal levels). The digital system converts the video image (and sound) to numbers, and broadcasts them in that form (i.e. digital). The digital system (using data compression) is able to produce a much clearer image than the original analog /NTSC system. Standard analog TVs will not receive the digital broadcasts, so TV stations will transmit both signals for the time being. Digital TV broadcasts will replace analog totally by approx. 2008. The analog transmitters will then be shut down, requiring older TVs to use a converter (set top box) to receive a picture. HDTV is the sharpest of the Digital TV formats. All High Definition displays have a wide -16 x 9 (meaning the screen is 16 inches wide for every 9 inches in height) aspect ratio screen. The wider screen allows the TV image to more accurately match our natural field of view, and allows the display of movies in their native (wide) aspect ratio, with smaller, or no masking bars above and below the image. All HDTV broadcast also have Dolby Digital sound, and can therefore create a stunning sense of audio realism. The HDTV system is able show much more detail (by a factor of up to 10 times by some measurements). While you will hear the usual marketing hype about the glory of HDTV, the actual difference you will see depends on the size of the TV you watch, and the distance from which you watch it. A 19 inch HDTV image viewed from 12+ feet away does not look a whole lot different than a 19 inch non-HDTV image viewed from 12+ feet away. In this case, we simply don't have the ability to see much of the additional detail in the image. A 60+ inch HDTV viewed from 8 feet or less, on the other hand, looks drastically different than the same size non-HDTV image. The high definition image can be so clear, that it seems like you are looking out a window at what is happening on the screen. Home Theater and sports fans love watching on the "big screen", so HDTV will have a big impact on them in the coming months and years. All Digital TV does not have the resolution (the ability to show fine detail) of HDTV, however all DTV will be an improvement over the analog/NTSC TV most of us are used to seeing. It's a good bet that many movies and sporting events will be broadcast in an HDTV format. How much additional HDTV programming that will be broadcast is still in question. Prices on near-HDTV (high resolution digital sets without the wide screen) 36 inch TV systems available now are around $2,600.00. Full blown big screen (53 inch and up) HDTV systems start around $4,000.00. These prices include the digital tuner and are ready to go. Watch out for HDTV "ready" systems that are being advertised by some of the big chains - they don't include the digital tuner (an additional $700.00+). For those interested in a more in depth look - Read On. HDTV - A Closer Look The more detailed HDTV image is a result of more information being transmitted - the additional data simply describes the image in more (or finer) detail. Digital compression allows the additional picture information to be squeezed into the same (6Mhz) bandwidth allowed for a single TV channel (analog or digital). What constitutes HDTV? There are two ways to indicate a display device's ability to resolve fine detail (it's resolution). The older method is to state the number of individual lines that can be displayed - before the lines become indistinguishable from each other. The newer method counts the number of individual pixels (or picture elements - the smallest dot, square or rectangle that can be displayed) by a given display device. The pixel method is better suited to a digital device - a pixel is one single element - easy for "things digital" to understand and control. A good way to visualize the pixel concept is to think of a sheet of graph paper, the image is created by filling in the squares (you must fill in the entire square or leave it alone). The smaller the squares (of the graph paper), the clearer and more defined the image. The more squares (or pixels) you can squeeze into a given area, the clearer the image you draw will be - on graph paper or the screen of a display device. To be considered High Definition, a display needs to draw nearly 1,000,000 pixels or more. Standard  (analog) TV displays only about 300,000 pixels, maximum (generally much less). HDTV displays 1,000,000+, - so you get "the picture". There are two HDTV formats being broadcast now, 720p (720 progressively scanned lines) and 1080i (1080 interlaced lines). TV pictures (on CRT, or tube type displays) are created by scanning an electron beam, from left to right (starting at the top) across and down (one line at a time) the screen, the intensity of the beam at any given instant, dictate the brightness of the image at that location. The more lines that are scanned, the clearer (sharper/more defined) the image will be - and the more pixels it contains. The interlaced format scans every other line on the first pass (this half full image is called a field), then starts again, at the top, and fills in missing lines on the second pass (another field). The two fields make up frame of video. The progressive format scans the full frame in one pass. So, why are two different formats being used?  The broadcast and consumer electronics industries can't get together and agree on a single format (that might be good for everyone - remember VHS and Beta). Anyway, which format is best - now that's a good way to start an argument at a video engineer's convention. The bottom line is, the 1080i can display finer detail, provided the is no movement on the screen (a still image). The progressive format handles moving images better, so there is no clear answer. All HDTV tuners can handle all DTV  formats (there are 18 in all), so you don't need to worry that the system you buy won't handle everything out there. Many set manufacturers are selling the tuner (receiver) as a separate "set top box", so, if in a few years, 1080p (or something else) comes into existence, you could replace only that component to upgrade (provided the display can handle the new scan rate). It is our opinion, that unless you want a huge image, say, over 100 inches, 720p or 1080i will provide all the resolution you will ever need. We can show you a 480p (not true HDTV) image on a 90 inch screen, that is very, very clear. The 480p signal, in this case, comes from DVD with a scan line processor (doubler). Another big question with HDTV is, how much of it will be broadcast. All "over the air" broadcasters, in the U. S., are required by law, to begin transmitting "digital TV" (DTV) signals within a few years. There is no legal requirement, however, that the signal be High Definition, lower resolution digital formats (like 480p or 480i) will probably make up the bulk of programming in the beginning. Our guess is that major sporting events and some movies, will be in High Definition, with news and most other programming being 480 (i or p) line digital. If you have seen Digital Video Disc (DVD) displayed (a 480i line format), you know that it is a big improvement over what we have been seeing broadcast in analog. The Direct Broadcast Satellite people are are providing HDTV signals now, but you do need new (satellite) hardware to receive it. Where this is all going is still in question, so, it might be wise to wait a year or two and see what shakes out. On the other hand, many HDTV sets available now have unbelievably clear pictures. These sets will provide many years of great service, and the prices have already dropped to levels equal to that of "top of the line" analog TV's. Also many current HDTV displays have "on board line doublers", so analog broadcasts and other current sources (DVD, DBS, VHS etc.) look much better than you have seen in the past. We're going to be seeing some great TV images in the very near future, so why not take advantage now. Our plan is to go into more detail here as we get time, so check back if you find all this interesting. Or Contact Us at ADVANCED AUDIO VIDEO with any questions. Phone 812 373 0734 Home