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DTV—What is it
and Island Ad-Vantages, 6/5/08, page 4 Digital Television is on its way and by February 17, 2009, it will replace analog signals now being broadcast by local television stations. This changeover will affect the way most of us have watched television since its inception in the 1950s. DTV brings with it a number of improvements along with a few headaches. Between now and February, I will try to explain what you need to do to prepare for the changeover. Monthly columns are planned through November, then twice a month December through February. I will also help you understand all the new television formats and the new class of televisions required to display the DTV formats. Before moving to Maine, my job at RCA was to recognize those various DTV formats and adjust the television display mode to display it correctly. RCA has been working on converting their TVs over to DTV and HDTV for several years. In fact, the mandate requires larger televisions to have a built-in digital tuner since 2005. Digital television differs from analog television primarily in the format of the signal that the television receives. The TV can receive the signal either directly through an antenna or indirectly through cable or satellite. Traditional analog television signals (known as NTSC) communicate the signal in a format that requires the full bandwidth of the broadcast channel. Analog signals are sent in real-time exactly how they were created at their source. Analog signals, by their nature, allow an infinite number of colors and contrasts, thus necessitating the full channel bandwidth for transmission. Digital signals, by contrast, compress the television signal using very complicated algorithms (known as MPEG) that allow for signals to be communicated using significantly less bandwidth. Digital television takes a snapshot of the analog signal and then digitizes and compresses the signal and sends it to your TV. Your TV (or a converter box) uncompresses the signal and then displays it on your set. The advantage of digitizing your television signal is that it uses less bandwidth so more information (such as High Definition signals) can be sent. Also, the digitized signal is not affected by some of the problems with analog signals such as ghosts and noise (“snow”). The disadvantage is that the digitizing and compression can create some distortions (artifacts) in the picture that maybe objectionable. Why did the federal government mandate the conversion to DTV? In a word, money. Because DTV uses less bandwidth than conventional analog television signals, the freed up bandwidth can be used for additional channels as well as other wireless services. Those of you with DTV compatible receivers may have already discovered some of those additional channels. For example, in addition to WABI Channel 5, there is also WABI HD channel 5-1 and The CW channel 5-2. The first channel is the conventional analog channel with the two additional channels being DTV channels. These additional channels are referred to as sub-channels and require an additional number added to the main channel to access directly. Between now and February 2009, there will be a number of changes in where channels are located since the analog signals are still being broadcast. After February 2009, the channel locations should stabilize. Cable and satellite providers can put these new digital channels wherever they want, which means you may have to hunt around some to find your favorite channels. The good news is that cable and satellite companies have already done the conversion process so if you receive your television signals through cable or satellite then you won’t need to worry about the conversion. If you receive your television signals through an antenna, either rabbit ears or a rooftop antenna, then you will lose your analog signals in February 2009. To receive the DTV signals you will need either a set that has a DTV (ATSC) tuner or a converter box. The converter box will convert the digital signals to the analog format (NTSC) so it can be displayed on your television set. In the next article, I will describe how the digital format compresses the television signal along with helping you cope with the conversion. Simmons is a physical science teacher at Deer Isle-Stonington High School and a former RCA engineer. Island Ad-Vantages, 7/3/08, page 4 With digital television coming in February of 2009, and I thought it would be helpful to understand what makes digital television different from the analog that we currently have and why the government has mandated the changeover. Digital television requires a complicated procedure to convert analog television signals into a digitally compressed format that allows several digital signals to be broadcast in the same bandwidth as a single analog television channel. The advantages of Digital Television are numerous but they also come with some problems that those watching digital television may have already noticed. Most of the problems are in the form of picture artifacts (or distortions). Some of the artifacts that you might notice are that the digitizing process takes time and since the picture and sound are digitized differently they may end up on your TV out of sync. Another artifact can be seen on images that have a lot of motion such as waterfalls. Before I describe that artifact let me tell you a little more about the digitizing and compression process. The digitizing and compression process uses motion picture expert group encoding, also known as MPEG. MPEG encoding uses algorithms that take into account that not much of the TV picture actually changes from one second to the next. Thus, MPEG encoding first sends a TV picture containing all the information (called p-frames). It then sends several intermediate transmissions (called I-frames) indicating what has changed from the last time. By not needing to send all the information the amount of bandwidth needed is considerably less. Getting back to the artifact, when there is a lot of motion the compression algorithms have a hard time keeping up and thus produce less sophisticated images resulting in motion artifacts. Another artifact, which is to me one of the most noticeable, is what is referred to as contouring. This artifact shows up even on images with no motion and occurs because digitizing a signal requires squeezing picture levels into a fixed number of points (analog signals have an infinite number of points). This means that if there is a sunset, for example, where the image goes gradually from light to dark (or changes colors) the digitizing process will need to pick a point that comes closest to each level of the sunset. When the picked point jumps to the next level a faint contour line appears. When the picture pans in or out the contour lines will appear to move to follow the brightness or color levels. One additional artifact, is that a digital signal is more tolerant of weak television signals because the signals are either present or not. If the receiver picks up even a weak signal it can usually produce a error free picture. The problem is there is a point where even the digital signal becomes to weak to be decoded correctly. At this point the picture becomes very intermittent and may even freeze for short periods of time. Another headache digital broadcasting creates is that it makes most VCRs obsolete. This is because they record analog signals and not digital signals. Also, since a digital signal can be recorded and played without degrading, you could create your own DVDs of the programs and movies if it wasn’t for the copy protection. The copy protection was added because the broadcasters knew that bootleg copies would be a big problem with digital television if it wasn’t protected. In the next article, I’ll talk about what changes are needed to take place in televisions to be able to decode the digital signals. Island Ad-Vantages, 8/14/08, page 4 With digital television coming in February of 2009, I thought it would be helpful to understand what makes digital television different from analog that we currently have, and why the government has mandated the changeover. When television was first introduced it was black and white and basically a souped-up radio with a display. Television seems like it has been around forever and to the younger folks it has. In the beginning, television had all kinds of problems, which have gradually been eliminated. Most of us can remember pictures rolling and having to adjust the vertical sync to get it to stop. There were also problems with ghost images that would cause multiple images on the screen. This was caused by the television signal bouncing off buildings and other things before reaching your antenna. One image was the signal going directly to your antenna and the second (ghost) was the image bouncing off of something else. The ghosting and syncing problems along with numerous others were fixed with technology and the digital age. Probably the biggest advance, other than color, was the remote control. The remote control as we know it and the modern television weren’t practical until the invention of the microcomputer. The microcomputer is basically your home computer stripped down to the bare essentials and then given only one program to run. Just about anything with a display in your home has a microcomputer controlling the gadget. The remote control and your TV both have microcomputers that talk to each other through an infrared or RF (radio frequency) link. With the addition of the microcomputer to the television, many things that were very difficult to do were now easily done and many were done behind the scenes to make your TV easy to use. For example, all the picture controls (things that adjust color, brightness, contrast, etc.) were individual controls that would have to be aligned at the factory. As the TV aged these controls would need to be tweaked by the customer to keep the picture looking correct. The microcomputer in your TV now adjusts those controls automatically and keeps them pretty close to the original factory settings. Of course, engineers had to keep adding bells and whistles to your TV. The on-screen display basically opened the flood gates on these bells and whistles. The OSD is the display that tells you the channel you’re watching, the menu to change your TV settings and close-captioning. We all know that the remote controls started out pretty simple: power, channel and volume. With the OSD, the remote controls needed to add buttons to access things easier. All those buttons made the controls very hard to use at first. Eventually the TV manufacturers somewhat settled on a consistent button layout. It wasn’t just TVs that used remote controls but also VCRs, DVD players, cable boxes and recently direct broadcast satellite receivers. This means that all of these devices needed their own remote control or you could change your TV with your VCR remote by accident. To help solve this problem, manufacturers added remote control codes for a whole host of devices in a single remote (i.e. universal remote). This is still a problem today and hopefully all the manufacturers will some day use the same code. All this technology made the transition to digital TV fairly straightforward for the manufacturers since they already had the microcomputer where a lot of the conversion takes place. Some of the missing pieces were the digital tuner, mpeg (video compression) decoder plus a variety of support integrated circuits. In the next article, I’ll discuss how the digital channels are organized. Island Ad-Vantages, 9/11/08, page 4 With digital television coming in February of 2009, I thought it would be helpful to understand what makes digital television different from analog, which we currently have, and why the government has mandated the changeover. The whole reason for the switch to DTV is that it will free up bandwidth because digital broadcasting takes less bandwidth to broadcast then analog broadcasting. Analog broadcasting uses 6MHz bandwidth per channel, which is a lot of bandwidth for a single channel. In contrast, chopping up the TV signal and transmitting it digitally can convert the 6MHz bandwidth into a bit stream of approximately 19Mbps. That bit stream can be used to carry anything but most likely it will carry MPEG-2 video streams and associated audio. The original analog 6 Mhz bandwidth channel, when converted to a 19 Mbps digital bit stream can carry multiple TV broadcasts; many stations use this capability to broadcast multiple “sub-channels” within the assigned digital channel. This concept of sub-channels is going to make for an interesting channel lineup. First of all, since the broadcasters haven’t switched to being totally digital they need to support the current analog channels but also need to broadcast their digital equivalent so folks can start getting use to DTV. To do this the FCC gave the broadcasters some additional bandwidth to broadcast their digital signals. The problem is that these new digital channels are usually nowhere near the existing analog channel. To help keep channel mapping more consistent, a system called the Program and System Information Protocol was developed to allow for channels to be remapped. So don’t get too comfortable with your current channel lineup because it will probably go through several iterations before it finally settles down. The good news about this PSIP re-mapping is that it will happen automatically requiring the television viewer only to keep track of their favorite channels in the interim. To help, most channels now broadcast some sort of logo indicating which channel you’re tuned to. The NBC peacock is a good example. One thing that will certainly change, and you will need to be ready for it, is hooking up your VCR and DVD players. A lot of folks still connect their VCR and DVD so that they need to tune their TV to channel 3 (or 4) to view the VCR or DVD. This method basically requires the VCR and DVD to broadcast their signals so that it can be tuned by your TV’s analog tuner on channel 3 (or 4). I would start looking into connecting your DVD and VCR through the composite inputs or ideally through a digital input such as HDMI. If you plan now for your future television viewing needs, including VCRs and DVDs, it will take this transition to DTV much smoother. Next month, I will talk about the minimum requirements that will be needed to be watching television after the transition date in February of 2009. Island Ad-Vantages, 10/9/08, page 5 With digital television coming in February 2009, I thought it would be helpful to understand what makes digital television different from analog that we currently have, and why the government has mandated the changeover. So with this change next February, what do I really need to keep watching TV? First of all, the February 2009 changeover doesn’t apply to cable and satellite providers since they are not using any of the bandwidth the FCC wants to re-allocate. Which means your current setup will still work after the changeover. Although these companies, in addition to the current channels, are also broadcasting more High Definition channels, which requires an HD compatible cable box or satellite receiver and a HDTV television to watch. In the near term, they are also broadcasting popular channels in both HD and standard definition so you will be able to watch those channels on your current analog television. If I was in the market for a new TV, I would definitely think about buying one that can display HDTV as well as upgrading my cable and satellite equipment to be HD compatible. Second, if you are watching TV through rabbit ears or a roof antenna and your TV doesn’t have a ATSC (digital) tuner (new TVs do), your TV will not receive broadcast after February 2009. Your TV will still work with your VCR and your DVD inputs, just not your antenna channels. If you never watch any broadcast TV and only use your TV to watch DVDs or VCR tapes then you have no worries. Otherwise, you have two solutions; one is to buy a TV that has a ATSC tuner built-in or buy a converter box (you’ll get a $40 rebate check from the government). The converter box will convert the digital transmissions to analog signals your analog TV will be able to receive. Obviously, buying a new TV with a built-in ATSC tuner is the easiest way to transition to DTV. A word of warning: there are TVs out there that are HDTV monitors and can display HDTV signals but do not have any kind of tuner at all (hence, the name monitor). If you have one of these HDTV monitors then you have it hooked directly to your signal source (cable, satellite, DVD, etc). Just don’t go buying one of these monitors unless you know that you won’t need a tuner of any kind. Next month I’ll talk about some of the TV brands and advantages and disadvantages of each. Island Ad-Vantages, 11/13/08, page 4 With digital television coming in February of 2009, I thought it would be helpful to understand what makes digital television different from analog that we currently have, and why the government has mandated the changeover. So with this change next February, what do I really need to do to keep watching TV? With the holiday season coming, and of course the Super Bowl, now would be a great time to buy a new TV (especially since the campaign ads are gone). Seriously, if you are receiving your TV signals through an antenna or your TV is on its last legs, you might want to look into getting a new one. Of course, TVs are expensive and the economy is a mess, but if it is an important part of your life than you can’t be without one. To help you with the selection of a new TV, there are a couple of things you won’t have to worry about. The first is that all TVs sold in the U.S. must now have a ATSC tuner (for DTV). Any TV you select will work after February 2009 as long as it has a tuner and isn’t just a monitor. Besides the size, the next big decision would be the display technology. There are basically, four technologies that are used in digital TVs. The CRT (cathode ray tube) is what almost all TVs were until about 10 years ago when plasma TVs showed up. LCDs (liquid crystal display) showed up just a few years ago as well as did DLPs (digital light processor). Plasmas are very complex but can be very thin with probably the best picture quality. LCDs are also thin and use considerably less energy than the plasmas but the quality isn’t quite as good. The DLP TVs are not as thin as LCD or Plasmas but have good quality at a lower cost. CRTs are still out there but you are seeing less and less because of their size, weight and disposal issues; I would not recommend buying one. The trend is toward LCDs because of their size, ease of moving, improving qualities and lower energy requirements. Beyond the display technologies, the most important requirement is that the TV will meet your needs. How much you plan on spending, where the TV will be located, how big your room is and what you will be connecting the TV to all factor into your decision. In selecting a TV, think not only about your current needs but also future plans since you’ll probably have the TV for a number of years. When you look at a TV in isolation it is hard to detect the subtle differences in picture quality. Try to find a store with several brands for comparison especially more expensive ones. This allows you to see how the one you’re considering compares to the next step up. Next time, I’ll discuss the ways TVs are connected to all those other boxes and why there are so many ways of connecting them together. Island Ad-Vantages, 12/20/08, page 5 With digital television coming in February of 2009, I thought it would be helpful to understand what makes digital television different from analog that we currently have, and why the government has mandated the changeover. So with this change next February, what do I really need to keep watching TV?
One thing that has always been confusing with customers is how to connect your TV to all of the other boxes that folks have in their entertainment center. In this article I try to explain what all of those connectors are used for and what do you really need. Probably, the most common way folks connect their TVs to other boxes is through the antenna coax cable. This connection method is the most problematic with the switch to DTV. The problem is that the antenna connector uses the same analog signal format that DTV is replacing. Many VCRs and some DVDs players transmit their information on channel 3 (or 4). To watch those devices you tune your TV to channel 3 (or 4) and when you’re not watching using those devices you just tune your TV normally. This will still work fine if you are using a cable or satellite system but if you are watching your TV from rabbit ears or roof antenna then you will need to make some changes. If your TV is new with a built in ATSC tuner (for digital broadcast) then you won’t need to change anything as far as your TV is concerned. There is still going to be a problem with your VCR if you use it to tune your TV channels. Confused yet? What some folks do is use their VCR to tune stations from the antenna and then rebroad cast them on channel 3 that their TV stays tuned to. Even if you buy a brand new TV with an ATSC tuner you will still have a problem if you tune your stations using your VCR. For those who use this kind of setup, make sure the tuner you use is an ATSC tuner. This may mean reconfiguring your setup to make your TV your primary tuner. What I have been describing is, those who connect their TV and other boxes, using coax cables, connected exclusively through their tuner inputs. This method will produce good HDTV pictures through the antenna to your HDTV TV but poor quality from your other boxes, namely your DVD player. To get great HD pictures from your DVD player you have a several options. The two newest ways to connect to your DVD player is using HDMI or 1394 (Firewire). Almost all new HDTV sets will have at least one HDMI input and most will have at least two. This connection method has the advantage that it not alone connects your HD video but your audio signals as well. HDMI connections also employ copy protection to prevent your from recording copyrighted material. DVI is very similar to HDMI except that it doesn’t connect up the audio and doesn’t have the copyright restriction. If you use a DVI cable you will need to connect the audio up separately. HDMI and DVI are digital video interfaces and the best way to connect digital material. The other digital interface is 1394 (firewire) and is more of a techie type of interface. Most Apple computers and digital camcorders/cameras use this interface but it is still fairly rare in TVs and is not expected to go much further. All other interfaces between TVs and other units are analog. They would include: YprPb, S-video and broadband. These work fine for analog but won’t provide the detail that the digital interfaces will. They all also require separately connectors for audio (like DVI did). Summarizing, to get the best performance out of your digital television and DVD players think about using HDMI connectors. Also, since Blu-ray has won the HD format video war, make sure your next DVD player/recorder is Blu-ray compatible. Next, month I talk about ways of making sure your system is ready to go for the switchover. 8. DTV—What is it and how will affect me? With digital television coming in February of 2009, I thought it would be helpful to understand what makes digital television different from the analog that we currently have, and why the government has mandated the changeover. So with this change next month, what do I really need to keep watching TV? With the DTV changeover happening February 17, I thought I would run through the list of things you should have done or do by next month. First to summarize, if you are currently watching TV through a cable or satellite provider then your TV viewing will not be affected. Secondly, if you recently bought a TV (since March 2007) then your TV will have a built in tuner (ATSC) that can receive the DTV signals. Actually, TV manufacturers have been including ATSC tuners in TVs over 36” since July 2005 and March 2006 for TVs over 25”. If you are not sure, the easiest DTV station to get is generally WABI-DT channel 5-1 and 5-2. If you are watching TV through rabbit ears or a roof antenna and you can get 5-1 and 5-2 then you are all set for the changeover. Well, at least as far as the TV is concerned. You may need to improve your antenna to get the rest of the digital stations but at least your TV is ready for the DTV broadcasts. If you are currently watching some rather weak analog stations (lots of snow on the screen), then your antenna may be too weak to pull in DTV signals. One disadvantage DTV signals have over old analog broadcasts is that they are either there or not. If the DTV signal is weak then the ATSC tuner and digital processing in your TV will not be able to decode the digital information successfully. Now assuming your TV is an older model and you don’t have cable or satellite then you have several choices. First, you can buy a TV with a ATSC tuner. There should be plenty of them out there in all price ranges. If buying a TV isn’t an option, then you can get a converter box that will receive the DTV broadcasts and convert them so your TV can receive them. The government will hopefully reimburse you for the converter box, assuming they still have money. Of course, your final option is to sign up for cable or satellite. That way you can continue to use your existing TV. There is a chance that February DTV changeover might be delayed due to the lack of funds for the converter box. The funds have been exhausted and there is a push to delay the changeover until the funds are available. Even if the DTV changeover is delayed you need to be prepared anyway. It is going to happen either next month or in the near future.
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