Tuesday
May112004
Guide to Buying HDTV
Tuesday, May 11, 2004 at 10:29PM TIP OF THE DAY
Guide to Buying HDTV
Everything you always wanted to know about HDTV, but were afraid to ask.
http://www.extremetech.com/print_article/0,1583,a=125421,00.asp
April 28, 2004
By: Loyd Case
Buying a digital capable television is an exercise in frustration and anxiety. It's not unlike Alice's trip through the looking glass, surreal and inviting, with promises of digital nirvana and dead-end traps for the unwary consumer. This guide should help you cut through the confusing jargon and conflicting claims.
What this guide is:
- A first step to understanding HDTV--as it is presented to the consumer.
- A glossary of terms, defined in a way that's actually comprehensible.
- A high-level overview of HDTV display technologies.
What this guide is not:
- A guide to what technologies offer the best image quality. We'll touch on image quality issues, but your eyeball will be the primary judge.
- A guide as to where to find HDTV source material and services. However, since the HDTV delivery vehicle may affect your choice of displays, we'll give you a brief overview of the main types of HDTV signal sources.
- An in-depth primer on the ATSC (Advanced Television Standards Committee) standard for HDTV.
With these thoughts in mind, let's move forward.
HDTV Overview
HDTV (high-definition television) has been in development since the 1960's, though it didn't really gain any momentum until the 1980's. A comprehensive definition of HDTV includes analog formats that are not currently used in the U.S. However, we'll focus on the digital side that's relevant to the U.S. market. On the other hand, not all digital television is high-definition. We'll discuss those differences shortly.
In fact, the Federal Communications Commission (FCC) has mandated that all TVs shipped in the US have digital-ready tuners by 2007. That's a pretty aggressive goal ? certainly more quickly than the adoption of color television. If we assume for a moment that the broadcasters actually make the goal of pure digital broadcasting by 2007, that doesn't mean every TV needs to be replaced. Instead, some people will simply opt for set-top boxes ? which will probably be in the sub-$100 price range by 2007.
Today, HDTV is being rolled out by broadcast television, cable providers, and satellite TV. All HDTV broadcasts are not created equal ? some HDTV streams are compressed more heavily than others to save on bandwidth. However, all true HDTV broadcasts do share common features:
- HDTV broadcasts either support 720p or 1080i (we'll discuss resolutions in a bit).
- They are purely digital in nature.
- They require dedicated HDTV tuners, which can decode the higher resolution broadcast. In the past, most HDTV-capable displays have required external tuners, but this year, we'll see quite a few units with built-in HDTV tuners.
It all seems pretty straightforward, right? Would that it were so.
HDTV Source Material
Before you rush out to buy your shiny new HD television, you need to scope you how you plan on acquiring HDTV signals. Let's look at the primary sources for HDTV material. This is only a high level overview, so you should consult your local providers for more in-depth information.
Note that you're not restricted to one broadcast type. Several companies make external tuners that will support both satellite and over-the-air broadcasts, for example.
Over-the-Air Broadcasts
This is akin to traditional broadcast television, except that the signals are broadcast in digital format, and offer the higher bandwidth needed for delivering HDTV content. Quality of broadcast HDTV varies from one region to another, or even within regions. When HDTV broadcasts were first initiated, some locales suffered from severe multipath problems. Reflections from buildings would cause multiple ghost images on the screen. That's been mostly solved.
If your primary source will be over the air broadcasts, you'll need to have a good antenna. One good place to start your search for an antenna is the CEA Antenna site. It won't give you brand names, but will list the best type of antenna for your particular location, based on building type and presence of nearby high structures.
What you'll need is either an HDTV with a built-in ATSC broadcast tuner or a display-only monitor and an external tuner.
Cable TV
Cable TV networks seemed to have lagged behind in delivering high-definition television. Part of that has been an infrastructure issue -- the companies had to invest in new capital equipment to be able to support HD. Part of the issue has been organizational. The cable companies wanted to avoid the proliferation multiple different delivery mechanisms. This was driven as much by the HDTV manufacturers, who wanted to avoid the early mistakes of digital cable, with multiple different set-top boxes that wouldn't work across geographies. So they worked through Cable Labs and developed a unified standard for cable HDTV.
The core standard is called CableCARD, which defines both a delivery and identification mechanism for cable HDTV tuners. Users of satellite TV networks will instantly understand how CableCARD works from the user perspective. The ID mechanism similar to the smart cards used in satellite TV systems.
Quite a number of HDTV manufacturers have committed to building in CableCARD-equipped tuners. If you're interested in obtaining HDTV from your cable TV provider, you'll eventually want either a CableCARD ready TV, or an external set-top box that supports the standard. Few HDTVs support CableCARD today, but many are expected later this year. As of July 1st, CableCARD will be required by the FCC for digital cable systems. Most cable systems will support first-generation CableCARDs later this year as well. You should note that the first-generation CableCARDs do not support interactive services (like video-on-demand) and you'll still need a set-top box from your cable provider to use those features. New "two-way" CableCARDs supporting interactive services are due next year. Some interactive services will still be available (for example, pay-per-view movies), but will require a phone connection.
Satellite HDTV Service
The two major satellite TV providers -- DirecTV and Dish Network -- have both been delivering HDTV content for some time now. Dish Network is even offering bundle deals that include CRT-based direct view or rear-projection HDTV displays. The only downside to HDTV delivery from these networks is that a substantial percentage of the HD signal is heavily compressed. Some satellite HD signals are compressed down as low as 5-8 megabits. This tends to have an adverse effect on image quality.
A new satellite TV service, VOOM, is stepping into the breach. Launched by Cable TV network provider Cablevision, VOOM is committed to delivering HDTV signals at a minimum of 12-13 megabits per second or better. The service is ramping up pretty rapidly, but it's still the new kid on the block. Whether it will succeed or fail depends on how many subscribers the service can sign up.
Recorded Sources
Two other sources of high-definition content are available. One is D-VHS. As the name implies, D-VHS uses tape to deliver content (mostly movies) in high-definition format. It may seem like an anachronistic delivery format in the age of DVD, but it has been well-received by high end home theater buffs. It is, however, a stopgap measure at best, as new technologies emerge.
The most interesting one is HD-DVR. TiVo, Dish Network and other providers are beginning to deliver PVR (personal video recorder) functionality for high-definition broadcasts. Note that high-definition recording can eat up 10 gigabytes or more of disk space per hour of recording, so it goes without saying that you'll want the biggest possible hard drive in these units.
Finally, we'll see high-definition optical discs arrive on the scene late this year, but a standards battle is brewing between the supporters of Blu-Ray (backed by Sony, Philips and many others) and High-definition DVD, backed mainly by Toshiba and NEC. Until this format war shakes out, it's unlikely we'll see lots of prerecorded discs arrive on your store shelves. Interestingly, players that support Microsoft's WM9HD will arrive on the scene later this year, but content support may be shaky.
DTV Versus HDTV
Let's consider resolution for a moment. To qualify as HDTV, the broadcast (and the display) must support 1080i or 720p. Specifically:
Short Description Details
720p 1280x720, progressive scan
1080i 1920x1080, interlaced
480p (Digital Television) 704x480, progressive scan
480i (Standard Definition TV) 704x480, interlaced
These are best case numbers. Some low-cost analog TVs cannot, in fact, actually deliver full resolution, standard TV images.
The key point here is that 1080i is interlaced. A full frame consists of two 1920x540 line fields, offset slightly. Your brain combines the two fields, so you "see" single, full frame. On the other hand, 720p is progressive, so the entire frame is output to the display. The field rate of standard 1080i broadcasts is 60Hz, and the frame rate is 30Hz, whereas the frame rate of 720p is 60Hz.
Which is better? Before we open this can of worms, bear in mind that both are considerably better than today's TV resolutions. However, Alvy Ray Smith, one of the luminaries in the field of computer graphics, makes a strong case that 720p is actually better. If you want to read more, check out his analysis of 720p versus 1080i.
Some degree of confusion exists when discussing Digital Television (DTV) versus High-definition Television (HDTV). Both have "DTV" in their respective acronyms, but they don't mean the same thing. HDTV is, in fact, a subset of digital television. HDTV is only 720p and 1080i. Digital television simply means that the TV signal is broadcast in digital format ? but the actual resolution can vary from 480i to 480p to 720p to 1080i. But only 720p and1080i qualify as high definition television. (Point of fact: at one point, an analog high-definition standard that supported 1125 lines of resolution, was proposed for the Japanese market.)
HDTV is compressed using MPEG-2 before it's broadcast. A properly compressed HDTV signal delivering 1080i content is about 19.2 megabits per second, but the actual bitstream rate can vary. Note that some content providers compress the signal to a greater degree, so you may see attempts to deliver HDTV streams as low as 5-6 megabits. Image quality suffers when this degree of compression is applied to the content. Unfortunately, there's no easy way for a consumer to determine the actual bitrate, other than seeing decreased image quality. In fact, many HDTVs don't even tell you the active display mode (1080i, 720p, 480p, or 480i), and no HDTV sets today can display all formats natively, which is a subject to follow.
The bottom line: when you're shopping for HDTV products, make sure they support either 720p or 1080i natively.
Resolution Confusion
The fact that two different, supported HDTV resolutions exists is the source of some confusion. After all, if you have a display that support 720p, how can it display 1080i? Any PC user with a multiscan monitor ? as most are, these days -- probably guesses that the display can sync to different resolutions. That's part of the story, but not the entire picture.
In fact, a 720p HDTV can display a 1080i image and vice versa. They simply downscale or upscale the image, as needed. However, since the image consists of multiple frames (or fields), then properly scaling the image is challenging. Some TVs handle scaling better than others. In fact, you'll see TVs with all kinds of oddball resolution figures. Here's a table of some randomly sampled, actual digital televisions, and their native resolutions:
Product Native Resolution
Panasonic TH42PA20UP 42" Plasma 848x480
Panasonic TH50PX20UP 50" Plasma 1366x768
Pioneer Pro1000HDI 50" Plasma 1280x768
NEC PlasmaSync 42XM2 42" Plasma 1024x768 (widescreen)
Samsung HLN507W 50? DLP Rear-Projection TV 1280x720
Sony KDF-60XBR950 60? LCD Rear-Projection TV 1386x788
Mitsubishi WL-82913 82? LCoS Rear-Projection TV 1920x1080
As you can see, actual resolutions vary all over the map. Of the six TVs we looked at, the 42" Panasonic and NEC displays don't offer true HDTV resolutions. But they will downscale HD streams to the native resolution of the unit. So as you're shopping, be aware of the resolution question.
The key is this: if you want a true HDTV experience, the unit you buy should natively support either 1080i or 720p. You may still get a pretty darned good picture out of a 1024x768 display, but it's not true high-definition. Be sure to check the native resolution of any digital display before you buy. Actually, only a small handful of TVs actually support (or come close to supporting) the true 1920x1080 resolution of 1080i, so sets claiming native 1080i really are not at that level in horizontal resolution.
When you ask the question of a store clerk, or peruse specs on a Web site, you need to be careful. Advertising and spec sheets are littered with terms like "Virtual HD," "1080p input," and other meaningless terms. Make sure you nail down the native resolution of the display, and that it's really 720p minimum. Otherwise, what you're getting is an image that's scaled to a lower resolution. It may still be a very good picture, but it's not true high-definition. Many low cost plasma sets are listed as EDTVs, and they are cheaper for a reason, usually around 852x480, and though they can look darn good for DVD content, they are not HD quality.
One final note: this year, we'll see a considerable number of fairly pricey displays that are truly 1920x1080 pixels. These are often labeled as "1080p." Note that no high-definition content provider actually broadcasts in 1080p, so 1080p displays will deinterlace a 1080i signal or upscale a 720p signal, as described earlier.
Display Technologies
Methods for getting the picture onto your screen are among the fastest evolving technologies in the consumer electronics industry today. The net result is a vast array of products, all with different feature sets and capabilities. The confusing morass of display types is probably the primary reason that people throw their hands up in the air and give up when trying to buy an HDTV today. If you read Nick Stam's HDTV Quest series, you'll get an idea of just how confusing it can be, even among technically accomplished people.
We're not going to cover the actual innards of the various display technologies in any detail. If you're interested in the inner workings of the various display methodologies, be sure to check out Alfred Poor's excellent article, "What's New with Displays" on PCMag.com. We'll offer an overview of the practical realities of the different technologies as they're implemented in today's products.
Monitor or Television?
If you walk into a store today, you'll find three types of high-definition displays:
- Monitors. Although you may see these referred to as "HDTVs," they are, in fact, not televisions, as they lack tuners of any type. If you buy a monitor, you'll need to add a tuner. Note that most cable TV and satellite set-top boxes are tuners too, but if you want to watch HDTV, you'll need an HD-capable tuner. Why would you buy one of an HDTV monitor? If you already have a HD-capable digital set-top box or satellite tuner, you really don't need an integrated tuner. You won't save a lot of money, though, by buying a monitor without an integrated tuner.
- HDTVs with standard NTSC tuners. This allows you to watch standard, analog TV off the air or through a set-top box. This may seem a bit odd -- why a high def TV with a standard TV tuner? This is mostly historical -- when these TVs were on the drawing board, off-the-air HDTV tuner technology was expensive, and the technology was evolving so fast that many manufacturers didn't want to risk integrating a pricey high-definition tuner that might be obsolete.
- HDTV with integrated high-definition tuners. The older models will likely have over-the-air, ATSC-only broadcast tuners, which require an antenna, and can only receive over-the-air broadcasts. Many newer HDTV displays shipping this year will ship with a HD cable ready tuner capable of handling the QAM (quadrature amplitude modulation) signal that cable broadcasters will use to pipe HDTV signals over your cable TV link. Note that you'll really want a CableCARD ready HD tuner if you really plan on buying HD cable service. CableCARD uses a type of smart card to identify and authorize the user of the unit. People who have used satellite TV services will recognize this, as the major satellite TV providers use something similar.
The CRT Question
Quite a number of CRT HDTVs exist, both direct view and rear-projection. You rarely see any of them defined as 720p; most seem to be identified as 1080i. Direct view televisions (i.e., the good old tube) max out at around 34" for a wide screen unit, while rear-projection CRT TVs can be 65" diagonal or more.
CRTs are purely analog devices. If you hook your PC up to a CRT HDTV, you might be surprised to find out that it can only support 800x600 resolution or, if you're lucky, 1024x768. At first blush, that seems to indicate that a CRT HDTV isn't a "true" HDTV. But since they're analog, they do resolve the full 1080i signal. Since 1080i is interlaced, the TV only needs to support 540 actual lines of resolution. The horizontal scan lines aren't treated as pixels by the time the electron beam paints the line. The gating factor is electron beam spot size, and the number of holes or slots in the tube mask. For example, Sony's SuperFine Direct HDTV offers an actual resolution of 1407 x 1080i. For cost reasons, however, the manufacturers don't build in electronics that will support a digital progressive scan image that's 1920 pixels wide.
CRTs do have other benefits. They're still the best displays currently available to resolve standard television. Part of this is because the analog nature of the CRT "masks" the image defects in NTSC TV. But CRTs can resolve better details in deep blacks, though the best digital displays can look pretty good. Also, CRT HDTVs have the benefit of being considerably cheaper (if bulkier) than their digital cousins.
In a purely cost/benefits analysis, CRT televisions are the best bargains currently. For the most part, they're cheaper than their purely digital cousins. The technology is mature and well understood, they offer excellent contrast and dark scene detail. Direct view CRTs also offer wide viewing areas. But they're bulky and heavy; consumers are finding flat panels and shallow, digital rear-projection TVs to be more attractive. Also, their advantages over digital displays are steadily diminishing over time.
Digital Display Technologies
More detailed overviews of the different fixed pixel display technologies follow shortly, but let's touch on a few common benefits and drawbacks.
- Cost. All these units are expensive. A 43," digital rear-projector costs nearly $3,000. A plasma or LCD display that can display true HD resolution (720p or 1080i, remember), can cost well above $5,000.
- Image quality in scenes with very low light levels isn't as robust as with CRTs. This is rapidly improving, as wider gamut decoders are released, but these types of emissive displays will have trouble approaching the low-light detail of CRTs for some time to come.
- They show every defect of poor quality transmissions. A lot of R&D goes into developing video processors that exist purely to mask or reduce defects in standard television. Although the future is digital, a vast amount of programming material exists today -- and will continue to be made -- using methods that work well in an NTSC analog environment, but don't look as good when translated to digital.
DLP Rear-Projectors
These types of televisions seem to have almost come out of nowhere in the last 18 months, mostly due to the efforts of Korean consumer electronic giant Samsung. However, other manufacturers, including Optoma, Gateway and even Sharp, known for its line of LCD TVs, will be shipping rear-projection DLP projectors.
All DLP rear-projectors currently shipping support 720p (1280x720 native resolution), and use one of several Texas Instruments micro-mirror display technologies, typically either the HD2 or HD2+ chip. Later this year, lower cost 720p units based on TI's HD3 chip will ship. HD3 is supposed to offer better low light detail, at a lower cost than the current crop of 720p TVs. In addition, units based on TI's "xHD3" chip, which will support a resolution of 1920x1080 (progressive).
DLP rear-projection TVs are typically shallow (less than 20 inches deep) and light (a 50-inch diagonal unit can weigh well under 100 pounds). They usually have a fairly wide field of view from side to side, but the vertical viewing angle is less robust. At this year's CES, Thomson demonstrated a unit based on technology developed by InFocus that's less than seven inches deep.
DLP TVs often offer very bright images, but will lose detail in very dark scenes. This makes them good solutions for a family room or living room with lots of windows and used for daytime TV viewing. But they're not as well-suited for movie buffs who like to watch movies in darkened rooms. Still, image quality is improving rapidly with every generation.
All currently shipping DLP rear-projectors use a single DMD (digital micromirror device). A DMD is built using semiconductor manufacturing techniques, and consists of thousands of tiny mirrors that reflect light directed to it from a bulb. A single DMD is really a gray-scale device. Color rendition is handled by a spinning color wheel that typically has six or more segments, each with a primary color or a shade of gray. The electronics in the TV handles the correlation between the particular color, the amount of light being reflected and the light level. The combination of reflected light and a rapidly spinning color wheel fools the eye into seeing a normal color image on the screen. You can find more technical detail on how DLP works at TI's DLP Web site
Some people are sensitive to the speed of the spinning color wheel, and can see artifacts created by wheel itself as it spins. This is commonly known as the "rainbow effect." You should definitely do some viewing tests on a variety of material to see if you're sensitive to this effect. However, even if you are somewhat sensitive, it's only prevalent in certain content. But it's definitely a factor to consider when buying a DLP projection TV.
LCD Rear-Projection
LCD rear-projection TV typically uses three high resolution LCD panels, each with independent color filters to resolve the red, green and blue portions of the light spectrum. Light is projected through the panels, then routed through an optical subsystem to the screen. Sony is the largest proponent of LCD rear-projection television, but other makers include Hitachi, Epson, Zenith (LG Electronics) and Panasonic.
LCD projection TVs tend to be somewhat heavier than DLP rear-projectors, but still considerably lighter than CRT TVs. Like DLP rear-projectors, they are fairly shallow, usually 22 inches or less for larger displays.
In the past, LCD projectors have been faulted for a noticeable "screen door" effect, in which the area between the individual pixels is visible and often highly distracting, particularly in bright scenes. Recent units have reduced this effect considerably. Current generation LCD projection TVs look seamless from a distance, though the lines are still visible if you look at the screen from a very close distance.
The price of LCD rear-projection units can vary all over the map, from just over $2,000 to over $5,000 for a larger unit. As with DLP rear-projectors, the larger unit pricing doesn't really reflect the actual cost of the unit, but perceived "value." Since the light engines in these projectors are similar, you're really paying for the larger screen real estate, plus a few additional features (more connections, for example).
LCoS
LCoS is short for liquid crystal on silicon. It's a way of building a small LCD device using silicon wafers as the substrate instead of amorphous silicon, which is the primary material for current LCD flat panel displays. Silicon wafers have advantages and disadvantages as a substrate, as Alfred Poor discusses , but the primary motivator is to use existing semiconductor fab space to build LCoS chips.
Like DLP technology, LCoS is reflective (LCD panels used in LCD rear-projectors are transmissive -- the light shines through the panels). The big news in LCoS, though, is Intel. As part of its digital home push, Intel will be building LCoS chips and light engines. The first Intel LCoS chips will support 1280x720p, with 1920x1080p following at a later date. The key feature, from the perspective of people who will be building TVs, is that the chip form factor will be identical between 720p and1080p, allowing the TV makers to leverage a single internal design for very different products.
It's Intel's stated goal to drive the price of fixed-pixel, HDTV displays down to well under $2,000 for a 30-36" TV by the fall of 2004. It remains to be seen if Intel can deliver on such an aggressive goal.
Philips, Toshiba and Mitsubishi have all shipped LCoS televisions, but the technology has been plagued by relatively poor manufacturing yields of the LCoS chips. To date, LCoS units have been priced fairly high, though Philips Cineos 55" TV can be found for a bit over $3,000 -- competitive with equivalent DLP and LCD rear-projectors. Toshiba has discontinued shipping its units. Meanwhile, Sony is readying its SXRD technology, an LCoS derivative, which may show up in products by the end of this year.
Plasma Flat Panel HDTV
Until recently, much of the attention on flat panel TVs has been focused on plasma technology. Plasma displays consist of thousands of tiny cells containing gases which are ionized by current passing through the cell. The ionized gas emits UV energy, which excites a phosphor on one end of the cell. Three cells -- red, blue and green -- make up a single pixel of a plasma display. More detail on how plasma technology works can be found here.
As we noticed earlier, the resolution of plasma displays vary all over the map, from "Enhanced Definition" (852x480, typically), to resolutions that exceed 720p. Most true HD panels are 42 inches or larger. Note that both Samsung and LG Electronics have announced large (70 inches or better), true 1920x1080p plasma displays, but these aren't' actually shipping quite yet -- and pricing is likely to be stratospheric. Plasma TVs, while thin, are heavier than digital rear-projection TVs and LCD flat panel televisions. A 61" plasma display can weigh in excess of 200 lbs.
Plasma panels have some advantages over digital rear-projection displays and LCD flat panel TVs:
- The viewing angle is wider than LCD flat panels and even most digital rear-projectors.
- Black levels are generally quite good, though not quite as good as CRTs.
- All other things equal, plasma displays offer better color fidelity than LCD flat panels, and better edge-to-edge accuracy than CRT displays.
- Plasma panels offer a faster response time than LCD TVs, so image ghosting is far less prevalent.
More variation exists in plasma panel resolution than just about any other fixed-pixel display technology. This creates a confusing array of display resolutions, along with terminology like "Virtual HD," which simply means its not really high-definition. Be sure to uncover the actual native resolution of the display before you buy. You may choose to buy a plasma panel that's less than true HD resolution (720p minimum), but it should at least be an educated decision.
LCD Flat Panel TVs
Today, plasma TV sizes start at about 32 inches and go up from there. LCD TVs top out at around 42-46 inches and go down as small as 15 inches. So while some overlap between plasma displays and LCD panels exist, both also cover market segments the other product type cannot.
We noted some of advantages of plasma displays earlier, but LCD have some advantages of their own. The chief advantage is brightness: LCD TVs are much brighter in bright light, so are well suited for daytime viewing in lighted rooms. Also, it's much easier to build a high resolution LCD panel. So we'll see true 1080p LCD panels at 42 and 46 inches by summer of 2004. Panel sizes of 50 inches may arrive next year, but not in large quantities. Even small LCD TVs, such as commonly available 17-inch wide screen units, offer 1280x720p resolution or better.
Be wary of LCD TVs that are not HD resolution, if you're shopping for an HDTV. Similar to "EDTV" plasma displays, a number of fairly large displays exist -- up to 30 inches -- that offer resolutions of 852x480. Some 20-inch units only offer 640x480 native resolution.
LCD TV manufacturers are working hard to overcome some of the shortcomings of LCD panels. Typical panel response times are down to 25ms or less, although true "gray-to-gray" response times are still pretty long. Samsung is talking about gray-to-gray response times of less than 10ms, but that particular technology probably won't arrive in the marketplace until 2005.
Also, the LCD color gamut isn't as wide as plasma or CRT TVs, but video processing technology has improved the color rendition and video image quality of LCDs substantially. Today's best LCD TVs offer very good image quality, though not quite as good as the best plasma or CRT image. In a brightly lit room, however, an LCD TV can actually look better than a good plasma TV.
HDTV Pricing
That sexy 61-inch plasma HDTV may be enticing -- until you realize that it will set you back as much as $15,000. On the other hand, a 60 or 61-inch digital rear-projector that's less than 20 inches deep may cost well under $5,000. And you can find 50-inch CRT rear-projectors for under $2,000.
The other issue is that the pricing landscape is shifting pretty rapidly. More plasma and LCD TV manufacturing capacity is coming on line this year, so prices should stabilize or even come down a bit. However, the cost of actually making the panels is fairly fixed, so big, thin displays will likely remain very expensive.
Digital rear-projectors, however, will be trending down the price curve this year. By year's end, we could see 40-inch, 720p rear-projectors as low as $1,500. That's approaching the price of lower-cost CRT HDTV units. So if you're in the market for these types of HDTVs, you should keep a watchful eye on pricing as new products arrive for the Fall shopping season.
Making the Connection
One other factor when buying an HDTV you need to consider is how you route the video and audio signals. Most HDTVs have a broad array of connection types, but certain choices may be preferable to others. This may seem like something you only need to worry about after you bring your HDTV home. But you really need to decide how you do this ahead of time. Which connection type can affect other peripherals you buy in the future and may even determine how soon your newly purchased TV becomes obsolete.
Connection Topologies
If you have a monitor, and want to connect to a digital set-top box, then you have several potential choices:
- Analog connection, via component video cable
- Analog connection via RGB connection (using VGA-style connectors)
- Digital connection, via DVI with HDCP content protection
- Digital connection via FireWire (1394a) with DTCP content protection
- Digital connection via HDMI with HDCP content protection
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Since almost all high-definition displays ship with component video inputs, it's a good fallback, even though it's not a truly digital signal path. The quality of the component video signal depends greatly on the digital-to-analog (D/A) signal conversion that occurs in the set-top box or HDTV tuner before the analog signal is sent to the HDTV. If the TV is a true digital display, an additional analog-to-digital step (A/D) occurs inside the TV itself.
A few TVs have VGA inputs, and some tuners or set-top boxes will have VGA-style outputs. However, this combination is fairly rare.
Given those conversion steps from digital to analog and back, it would be great to keep the signal entirely in the digital domain. In fact, the industry is moving rapidly towards an all-digital transport chain. No fewer than three different digital delivery mechanisms exist for moving the signal from the digital tuner to the HDTV.
The first, and earliest method is FireWire (1394a). For awhile, it looked like FireWire would become the de facto standard, especially as High-bandwidth Digital Content Protection (HDCP) was added to systems that supported FireWire. That would have been great, as FireWire can also act as a network mechanism, allowing multiple peripherals to connect. Alas, it looks like FireWire will gradually fade away.
However, a number of manufacturers still support FireWire. Most notably, Mitsubishi's line of HDTVs support the standard, and a number of set-top boxes and digital TV tuners will deliver high-definition content over FireWire. A few high end DVD players and A/V controllers also support the standard. FireWire can even deliver digital audio signals as well as digital video.
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A more common method to deliver just the video part of the signal is DVI-D. DVI, or Digital Visual Interface, is commonly available in many LCD flat panel computer displays. DVI-D, which passes only digital signals, is the flavor of choice for many HDTV displays today. Every HDTV with DVI supports HDCP content protection, required by sources which deliver DVI-D signals.
However, DVI is also being phased out for yet another connection, known as HDMI (High-definition Multimedia Interface). HDMI is a very high bandwidth (up to five gigabits per second) standard, and also supports HDCP content protection. This is much higher bandwidth than FireWire, so its lifetime is potentially greater. The internal video signal is also compatible with DVI, so integrating HDMI into new hardware is fairly straightforward. Unlike DVI, HDMI also serves as a digital audio transport, and can serve up full 7.1 channel digital audio as needed by the A/V electronics.
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Your best chance of avoiding obsolescence is to buy peripherals that support HDMI. Bear in mind that HDMI is fairly new, but the consumer electronics companies are aggressively deploying HDMI-equipped displays, A/V receivers, DVD players and set-top boxes this year. However, if you don't own HDMI gear currently, other connection methods will be supported for years to come, so don't start tossing out all you gear immediately. In fact, if you buy a DVI-equipped HDTV today, simple HDMI-to-DVI converters will be readily available.
Other Resources
Shopping for HDTV can be a time-consuming and confusing process. We've covered the barest basics to get you launched on your own personal HDTV quest. However, other great sources of additional information are available on the Internet. We list just a few here.
- AVS Forum: AVS Forum is a tremendous source of useful, but also often conflicting, information. That's because it's a user-driven forum, with hundreds of home theater enthusiasts participating. It's always useful to post a question about a product you're thinking about buying, as the forum members offer ready technical advice and reasoned opinion.
- HDTVPub: This is a rich source of information on who's broadcasting in your area, plus general information on HDTV displays.
- DigitalTelevision.com: This DigitalTV site offers news and information on what's going on during the transition to digital television. Includes links for both TV professionals and consumers.
We've only barely scratched the surface of HDTV technology in this introductory overview. Once you bring your HDTV home, issues like image calibration, tweaking the audio setup, how to integrate an A/V preamp/processor or receiver with the TV all add to the volume of stuff you have to know. It's a far cry from buying that 27-inch NTSC TV and plopping it in the family room.
The situation is made more difficult by the cost. Even low cost HDTV is still considerably more expensive than a basic TV. However, the cost of smaller units is dropping rapidly. Recently, one PC Magazine editor bought a Samsung 26-inch widescreen HDTV for under $700. But once you get the HDTV, it's all to easy to start ratcheting up the ante. Do you want a full home theater A/V setup, with six or seven speakers and a subwoofer? What about specialized seating?
As these thoughts whirl through your head, just take a deep breath and focus on what your goal is. Maybe you do want the best possible home theater system, right down to the popcorn maker in the corner. Or maybe you just want to be able to watch Monday Night Football in high-definition. Just remember to take your time and look at a lot of different TVs before making your choice. Your patience will be well rewarded.