Digital TV in the U.S.
This is part of IEEE Spectrum's Special Report: The Day Analog TV Dies
Of the brave souls who bought any of the 13 176 digital television sets shipped in 1998, let it be said that never have so many paid so much for so few hours of programming. Sets went on sale as early as August, yet some buyers live in markets where there is no digital TV (DTV) to watch at all—and will not be for some time. That includes San Diego, Calif., where retailer Tom Campbell told IEEE Spectrum that his aggressive Dow Stereo chain in 1998 delivered nearly 100 sets to customers unlikely to receive terrestrial fs until late this year. Conspicuous consumption? Perhaps. Faith in the promise of progress? Certainly. But though digital programming is still offered in only a minority of locations, consumers have good reason to buy the US $7000-plus sets as a down payment on the future. For one thing, manufacturers have configured the digital models for the early market, and for another, they have included desirable features that can be exploited in the meantime.
In their initial marketing, TV makers have given consumers flexible ways to acquire DTV that promise instant gratification while assuaging fear of obsolescence. Some of the mostly large widescreen rear-projection DTVs are known as integrated sets because they have the DTV decoder built in. But the greater selection of models marries an optional outboard module, or set-top box, for receiving the digital broadcasts, to a widescreen monitor. Bothe types of sets can process any of the 18 standard- and hi-definition TB (SDTV and HDTV) signal formats approved by the Advanced Television Systems Committee (ATSC), although it is likely only four will be transmitted. The sets also receive and display the current National Television Standards Committee (NTSC) format.
The HDTV-ready monitors can display the 1080 interlaced lines, referred to as the 1080i format, of what is now the highest-resolution format sanctioned by the ATSC. Besides 1080i, there is the HDTV-level 720p, with 720 progressively scanned lines, and two standard-definition 480-line formats, namely 480i interlaced and 480p progressive.
The modular monitor-plus-set-top box approach is elegant enough to induce some customers in areas where digital TV is not yet broadcast to buy a new, DTV-ready display now, but to defer the purchase of the set-top box until digital broadcasts arrive—by which time the box is likely to be less expensive [see "What's on and how? "]. Issues such as cable delivery and conditional access for possible pay-DTV might be settled by then, too.
In the meantime, buyers of either type of DTB-ready set will be able to view ”enhanced” images from the beginning. Virtually every manufacturer boasts some signal-processing package designed to improve analog broadcasts and cable signals. The same package also enhances signals from home video sources, such as analog video-cassette recorders (VCRs) and laser-disk players, plus existing digital devices like satellite TB and the digital versatile disk (DVD) players.
Yet another aspect of the modular DTV arrangement might appeal to recent buyers of a high-quality analog TB who happen to reside where DTV is broadcast. Buying just the outboard decoder and adding and antenna [see ”Ghost story: antennas for DTV ”] would enable those households to receive terrestrial DTV. Granted, on-screen resolution will be limited to the capability of the existing display, but digital reception will eliminate ghosts and other distortion artifacts found in analog broadcasts.
Viewers of widescreen 16:9 DTV on an analog set will, of course, have to do so on a canvas of 4:3 proportions, but that might be acceptable if the set is a projection model. As most such TVs have a sizable display, the letterboxed 16:9 DTV program will still appear large when screened. This holds for another modular option TV makers offer—4:3-proportioned DTV-ready rear-projection sets, which can display the 1080i resolution of HDTV, but cost less than widescreen sets. For the record, programming sent over the DCTV channel will maintain a 4:3 ratio, if that’s how it was recorded. On widescreen sets, the centered image will be framed by dark pillars on either side, yet most DTVs offer some option for stretching the image gradually, either uniformly, or at the extremes, in order to fill the screen.
Although integrated DTVs seem a less flexible option for viewers in non-DTV markets, some models offer alternative means for receiving digital signals. These are the sets from Hitachi, Thomson (ProScan and RCA brands), and Toshiba, which feature built-in tuners for receiving DirecTV satellite transmissions. The satellite programmer was scheduled to begin carrying high-definition telecasts 6 March. DirecTV enables DTV makers to market throughout almost all the United States because its signal can be received by all contiguous 48 states. This marketing has implications for DTV pricing as well. Price tags will surely drop in any case, but might do so faster with the volume efficiencies that derive from manufacturing for a national mass market.
Large rear-projection sets dominated initial DTV offerings (the $9000 wide-screen 34-inch set from Tokyo’s Sony Corp. being the lone direct-view selection), but more tabletop DTVs are in the offing. So-called flat-tube models, of the kind shown by Daewoo, JVC, Konka, and Panasonic, will be costly because of the expense of non-curved glass and the need to import the tubes. But all eyes are on Thomson Consumer Electronics, Indianapolis, Ind., whose U.S.-made 38- and 34-inch tubes with a slight curvature will make for ”affordable” direct view DTVs this fall, according to the company. Those sets will be so-called integrated models (complete with internal decoder) and include the DirecTV receiver, which Thomson also incorporates in its upcoming $649 outboard decoder.
At the other end of the direct-view price spectrum are the flat-panel plasma displays, which are currently in the five-digit dollar range and only offer standard-definition TV resolution. But HDTV plasma mode3ls are coming later this year from Fujitsu, NEC, Pioneer, and Thomson—which cautions that its widescreen 50-inch ”flagship” will not be cheap.
Neither will yet another recent, non-cathode-ray-tube display technology: liquid-crystal display (LCD) rear projectors. Still, their $6000-or-so price tags are less likely to induce shock than the plasma screen HDTVs. Samsung is readying 43- and 50-inch HDTV models in that price range; Sharp has a 60-inch rear projector on tap.
DTV for the PC
Probably the first low-priced DTVs will be personal computers (PCs) rather than traditional TV sets. Much of the computational power required is already in the box, and PC monitors already perform the progressive scanning that is suitable for SDTV-480p display and, possibly, the HDTV-720p format. Several companies have announced the approaching availability of DTV decoder cards for PCs. Some of these decoders also include a TV tuner to receive the broadcasts, although others would require an add-in TV tuner card.
Among those announcing DTV products for the PC are Panasonic (Matsushita Electric Corp., Osaka) and Compaq Computer Corp., Houston, Texas, which jointly developed a DTV tuner-decoder board that they will make available to all PC manufacturers. Zenith Corp., Glenview, Ill., in conjunction with partner SkyStream Corp., Mountain View, Calif., has demonstrated a PC card that handles DTV datacasts as well as video entertainment from either broadcast or cable sources. Separately, Zenith’s corporate parent—Korea’s LG Electronics—has demonstrated its own chipset decoding signals for SDTV monitors. Royal Philips Electronics NV, Amsterdam, the Netherlands, also has announced the availability of a DTV ”reference” board, this one for installation in the PCI slot of PCs. That board has the backing of microprocessor giant Intel Corp., as it leverages the computational power of the Intel Pentium II processor in the PC.
Not to be left out, Tokyo’s Hitachi Ltd. has said that its all-format decoder, first announced in 1995, will be embedded on chips jointly designed with Equator Technologies Inc., of Campbell, Calif. The chip’s key application would be to downconvert HDTV formats for viewing on SDTV monitors.
Withy its MPEG-2 compression capability, DTV offers a great amount of flexibility in how broadcasters use their 6-MHz pipeline [see ”Squeeze plays—DTV compression and scaling”]. They can send a single channel of HDTV programming or use the lower-resolution SDTV and split the channel to simulcast multiple programs, including data transmissions. It all depens on which digital picture format the broadcaster uses [see "DTV formats," and how the station allocates bits in the data transport rate of the channel. Currently, the 6-MHz channel can transfer 19.4 Mb/s of data.
Broadcasters who opt for a multicast strategy will have to determine what combination of compression ratio and data transfer rate delivers the best picture quality for a given program. Sports and other fast action programming will require more bits and faster transfer. Movies or shows, where the background changes less, consume fewer bits and could be broadcast at lower data rates. So, whereas a ball game sent in HDTV format would occupy the entire channel, it might be possible to send two or three at SDTV resolution, or two or more alternate camera perspectives of the same game. Conversely, two HDTV movies or sitcoms might be able to share the channel; more could be broadcast as SDTV.
Given the flexibility of the ATSC system, it is even possible for a broadcaster to mix different programs of high and low data-densities and transmit them simultaneously as SDTV sub-channels. The 19.4-Mb/s channel could fit, say, a data-hungry sports program at 8 Mb/s, plus perhaps three leaner (3.8 Mb/s) programs, like a newscast, soap opera, and a movie. Meanwhile, since all four are unlikely to use all the bandwidth at any one time, any temporarily idle bits could be gainfully employed elsewhere through statistical multiplexing (or stat-mux).
Alternatively, besides being borrowed by the ball game from the soap, unused bits could be assigned to carry data to the TV. Such opportunistic bits might update information for an electronic program guide or provide scrolling text related to the onscreen show. Among the networks, the Public Broadcasting Service has said it will use its DTV channel for datacasting to raise revenue, inasmuch as the government-funded network cannot sell advertising. The network already draws income from selling data space in the vertical blanking interval (VBI) of its signal. Note that the Federal Communications Commisssion does not mandate how broadcasters use their DTV allocation or divide the bit-stream. The only legal requirement is that at least one channel of digital programming be free of charge.
The multicast option gives broadcasters a chance to sell some program channels by subscription, much as cable and satellite TV do. But two obstacles, one political and the other technical, will slow the race to the bank for quite some time.
As to the first, the prevailing sentiment in Congress is for the public airwaves to be used for the best possible pictures—HDTV. So, legislators have demanded broadcasters pay a fee for any pay-channel revenue they make on airspace they received free. The second roadblock, albeit temporary, is that pay-TV broadcasts would need a conditional access system at the set, similar to those of cable and satellite systems, in order to address the household and tally te bill. Like datacasting, conditional access has yet to be resolved, and in a way, any feasible technical solution is tied to yet another open issue: copyright protection.
Intellectual property owners (read Hollywood) demand that their content be protected from unauthorized copying. The same digital technology that produces crystal-clear originals could also yield picture-perfect replicas. Hollywood has the clout to hold the DTV transition hostage, for besides political lobbying power, the studios can simply block content release and refuse to license any compelling entertainment for digital broadcast.
For some time now, the multi-industry Copy Protection Technical Working Group, which holds its meetings in Burbank, California, has been studying methods for copyright protection that include encryption, device authorization, and digital watermarking. But the politics are at least as complex as the technologies under review—and maybe more intractable. So, it is unlikely that anything will be resolved this year in time for inclusion in next year’s DTVs.
Meanwhile, last year’s sets might be upgradable when the solutions arrive, as most manufacturers have built them with a trapdoor, in the form of a proprietary data port for adding hitherto unimplemented features. Finally, what happened to the digital VCRs or other devices to record all this broadcast eye-candy? [See ”DTV and time zones .”] Well, just think copyright. Batteries of attorneys are just waiting for the lawsuit that will inevitably greet the first electronics manufacturer to announce such an ”infringing” device.
See our sidebar, "DTV overseas" for more on DTV outside the U.S.
Spectrum editor: Paul Miller
To Probe Further
For more articles and special features, go to IEEE Spectrum's Special Report: The Day Analog TV Dies.