HDTV At The Front Lines
Dear Gary The birth of HDTV has been an interesting yet difficult experience. I own a company that specializes in the calibration and optimization of HDTVs. I have been feverishly working on HDTV sets and now it’s April 1999 and I am finally at the point where all my labors are starting to bear fruit. I will take you through some of the wonders, difficulties, problems and solutions of this process. First, the good news. I am pleased to report that a number of my clients are enjoying a steady diet of fabulous clear HDTV programming including live sports, movies, and the occasional TV program. I am in Long Island, New York and kudos go to the magnificent efforts of Cablevision of Long Island, Time Warner of New York, Unity Motion and WCBS-TV. My clients own a mix of HDTV-ready front and rear projectors by Toshiba, Zenith, Runco, Samsung and others. They are receiving HBO and Madison Square Gardens (MSG) via cable, Unity Motion via satellite and WCBS-DT terrestrially on Long Island and HBO and WCBS-DT via cable in NYC. The pictures are outstanding. The best picture quality is programming that is video based rather than film based. It possesses a grain free, noise free picture with remarkable realism. Whether a live sports or a news show like 48 Hours; the quality of video is very lifelike. My goal as an Imaging Science Foundation (ISF) calibrator/optimizer of HDTVs is to provide the customer with the highest level of performance his/her TV is capable of. It has not been easy. There have been many potholes along the road to magnificent reception. I will not only point them out but also provide the solutions I have found. The problems fall into two categories. First, I will go over transmission/reception problems and then I will explain the equipment problems. The transmission/reception problem I will start with is called upconverted HDTV. In New York, WCBS-DT is taking their regular 4:3 480i signal (when the program is not recorded in 16:9 true HDTV) and upconverting the programs to 1080i, stretched to wider than 4:3 (1.33:1) but not as wide 16:9 (1.78:1). The result is a picture that does not horizontally fill the screen on either a 16:9 or 4:3 set. What you end up with is a proportioned smaller 4:3 picture than the screen size on a 4:3 TV —sort of a “framed picture inside the screen.” To make matters worse there is no consensus of opinion between the HDTV set-top box companies and the TV makers on displaying HDTV on a 4:3 TV. The result is that some 4:3 sets and set-top box (STB) combinations display HDTV distorted (looking tall and skinny yet covering the full vertical screen). In other words, some HDTV makers feel that the STB should adjust the proportion of the set in HD while some STB makes feel that the set makers should have made the adjustment. I have brought this problem to the attention of the manufacturers and they need to work it out. The easy solution for now is to buy the set maker’s own STB, it will be totally compatible. If you want to mix the makes of the two you need to first check it out to avoid incompatibility. In the future, I feel the manufactures need to put HDTV stretch modes in all their sets, similar to what they do now on their 16:9 sets. This way the viewer can always have the option of always totally filling the screen, undistorted, if desired. How about it set makers? The most frustrating problems that I have encountered have been bad reception. With our old analog tuners we just plug in and play to see if the picture is good, bad or in-between. With a HDTV it’s wait and see. Every STB I have used has to first scan the broadcast spectrum before displaying a picture. If it does not get a lock, there will be no picture. Since you are effectively blind to whether there is a picture or not till you see it, the whole process is by trial and error. In Manhattan, the urban HDTV enemy, called multipath, plagued me. In the old analog days it was called ghosting. It is a result of the HDTV signal reflecting off the many tall buildings. In HD, the result is no picture (and no lock in the STB’s memory) or a mosaic breakup along with an audio breakup. I have found two solutions to this nightmare. The first is a new type of indoor antenna that was shown in prototype form at the January Consumer Electronics Show (CES). It looks like a 9-inch cube and it virtually eliminated the multipath picture killers when I tested it in NYC. This antenna should be available soon by Terk, one of the leading makers of indoor antennas. The second solution was Time Warner Cable of New York to the rescue. They started transmitting both HBO-HD and WCBS-DTV over their cable system in the same form that it is being broadcast. Just plug the cable from the wall into the STB, scan and lock and viola, HDTV. The last reception problems I encountered were audio dropouts and video dropouts. When I started using STBs in December 1998 these were occurring all the time. The audio difficulties were a combination of reception problems and encoding changes on the broadcast end. All parties involved were very forthright and I am happy to report that audio dropouts are now history. You can now listen to beautiful Dolby Digital 2.0 (Dolby Surround-encoded) on movies and TV programs. Later this year, I am told that the broadcasters will switch over to Dolby Digital 5.1. I am looking forward to it. In the mean time, the digital sound is terrific. The video dropouts look like brief freeze frames lasting 2-6 frames or no more than a quarter of a second. This problem is also being resolved by the broadcasters. In the past week, I have only seen it occur on HBO-HD. When I started looking at HBO about three weeks ago, freezes occurred about every twenty minutes. Now they are happening about once a movie or about once in two hours. I have not spoken to HBO but since the freezes are so infrequent and they don’t occur any more on MSG or CBS, I am sure they will be excised completely by the time you read this. The manufacturers have designed some fantastic remarkable products. Due to various factors, they are not performing the way they could “out of the box.” Fortunately, most of these problems can be corrected and eliminated. The vast majority of the HDTV-ready sets sold are of the rear projection variety. I will concentrate on them. The first problem I have encountered with many rear projection HDTVs has been imprecise focus. I have discussed this problem with some of the vendors and they are working on the problem. The way most RPTVs are optically focused is by using a substitute screen on the production line that has large holes cut into at the bottom of the screen. The production line worker sticks their hands through the hole and moves the lens barrel back and forth until each of the lenses of the red ,blue and green CRTs are focused. The problem lies in the fact that the holed screen might not be set at precisely the same focal plane as the actual screen that will be installed at the factory. If it is the slightest bit off of the same focal plane, the definition drops perceptibly. The solution is to examine the individual set. If optical focus is off, I refocus it. The set must be on to do this and the chassis of all TVs are electrically hot with high lethal voltage. Leave this up to a trained professional and don’t try this yourself. The other type of focus is called electronic focus. Unlike optical focus, (which has been a hit and miss situation as far as set to set accuracy is concerned) electronic focus has been off on 100 percent of the HDTV sets that I have ISF-calibrated and optimized. This situation is a continuation of the manufacturers purposely defocusing more apparent brightness and less noticeable (to a novice) convergence errors. All of the HDTV sets I have optimized/calibrated have significantly sharpened as soon as they are electronically focused properly. I believe that eventually the practice of intentional misfocus will go the way of the buggy whip. In the meantime, it’s a procedure that gives instant benefits to all sets. The electronic focus is hidden behind a panel on sets as to keep unqualified hands away. The next area of problems is called raster geometry. This simply means that the picture will be properly proportioned and that straight lines stay straight and not bent or distorted. The problem lies with the fact that most companies in the past only had to be concerned with one set of settings, namely 4:3 NTSC. Now even the lowest-priced HDTV ready set has at least two sets of memories and therefore two raster settings and many of the sets have three, four or five. All of the raster memories must be set properly from edge to edge. Due to the fact that true HDTV is 16:9 and not 4:3, all HD programs appear letterboxed on a 4:3 HDTV-ready set. It is very apparent when theses black bars are bowed. Manufactures have been working on new test patterns and better quality control to get this under control. The problems seem to be very consistent with certain makes and models being almost always off and others being almost always right. Fortunately, all companies have had the wisdom to put service adjustments in all the sets so these problems are all curable with the help of a qualified servicer. All these adjustments can be made in your home. Once this is completed, another definition destroyer rears its ugly head; convergence. All the focusing and raster adjustments play havoc with the perfect overlaying of the red, green and blue color content that makes up the high-definition picture. A picture that is slightly misconverged will have its picture sharpness degraded down to normal NTSC definition. If it is further off, you will see red or blue halos around objects on the screen. A novice will describe it as a blurry picture. I attended a HDTV demo at a local appliance store and a customer remarked that the NTSC sets around the HDTV set were sharper. I explained that this HDTV set was out of convergence and that it was not what a high-definition picture should look like. The ability to make the convergence perfect is the key to getting the highest resolution possible. Without the ability to do this, you will never get the sharpness and high-definition you paid for. The ability and ease to get the set perfectly converged has really created a completely new set of problems. HDTV operates at a different scanning frequency than NTSC or line doubled NTSC. There is a different convergence memory built into every HDTV for this scan rate or sync. Even if the HDTV’s convergence was set perfectly at the factory, it will be off in your home. The earth’s natural magnetic field and other factors cause this. Unless you live next to the factory, the magnetic field will be different enough in your home to create convergence havoc. So while the set might be close to adequately converged for NTSC resolution out of the box, it is way off for the precision needed for HDTV. The solution is to converge the entire picture area of the set, not just the center which has been the only point you could precisely converge on many of the previous NTSC sets. This is where a problem arises with some HDTV sets. Most, but not all of the HDTV sets have what is known as full screen point convergence. This feature allows the calibrator/ optimizer the ability to get the sharpest most precise picture across the entire screen. In order to tune it, the calibrator/optimizer requires that the set display a grid pattern. If not, he must hook up an external HDTV signal generator. All the sets that I have seen that have point convergence also produce their own grid test pattern. The optimizer or set owner must also hook up a HDTV set-top box in order to create the proper sync signal for HDTV. Once this is done, the set can be very precisely converged. Unfortunately, at least two companies marketing HDTV sets do not include either a grid pattern or a full screen point convergence feature. These sets require a HDTV signal generator, which currently sell for $8,000 and up. This other type of convergence is called analog/digital and is very difficult and time consuming to perform properly. It is almost impossible to perfectly converge these sets and to come fairly close is very tedious work that requires a lot of prior experience. Check out the type of convergence the HDTV set has before you buy. If it has analog/digital make sure someone in your market area is equipped with a HDTV signal generator and the expertise to converge this type of set. If not, the set can not be converged properly. Color is the next area. With a pattern generator and a color analyzer, the white balance can be set, however, the manufacturers have not created separate internal memories for the HDTV’s STB inputs regarding the white balance. They are close, but with all HDTV sets I have set up, I must choose to ideally optimize for either NTSC or HDTV. The manufacturers need to either make color for all inputs and scan rates consistent or provide for separate adjustments. The good news is that differences I have observed are considerably less than the amount the sets are off “out of the box.” The end result will be a vast improvement. There you have it. If you want to join the group of HD pioneers, you now know what to expect. With the help of an Optimizer/ISF Calibrator, you too can be enjoying a steady diet of the most beautiful video images you have ever seen, every day.
Gary Merson - Home Theater Perfection Long Island, New York
Editor Gary Reber Comments:
Thank you, Gary, for a most informative report with recommendation on obtaining good pictures with first generation HDTV signals and displays. I am sure our readers will appreciate the valuable insight you bring, based on real world experience as a top-notch Optimizer/ ISF Calibrator. I know our readers would like to hear from you in the future about your experiences with HDTV at the front lines.
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