TVs Today
So far we've been concentrating on the audio aspect of the
home theater on the assumption that most people already have some form of video display
and want to enhance its performance with good sound. As assumptions go, that one's
probably more valid than most, but it conveniently ignores how complex the whole subject
of television has become in the early days of the 21st century.
In the good old days, a TV was a box -- most likely a
direct-view picture tube -- and the biggest question confronting most consumers was how to
hide it when company came. These days, we have direct-view monitors, rear-projection sets,
front-projection systems with separate screens, plasma monitors, and a question of almost
Shakespearean proportions: TV or HDTV?
Ah, that's the question!
Each choice deserves an essay of its own, but before we
start we need to look at the big picture (so to speak), so this time out we'll survey the
whole scene and then we'll break it down and -- over the next few months -- explore the
individual choices in more detail.
First, let's look at how TV currently works. Whether you
use an antenna for over-the-air (OTA) reception or use cable or a satellite receiver, your
TV (in North America, at any rate) employs a protocol known as NTSC (National Television
Standards Committee). This mandates a composite signal with a refresh rate
of 60 interlaced half-frames per second. In other words, the signal's red, green,
and blue color elements are mixed together as a single element and that picture is
broadcast in two parts which alternately restore themselves. Each frame is divided into
two half-frames, each of which contains every other line of the complete image. When those
two images are switched back and forth rapidly (60 times per second), the eye/brain persistence
of vision mixes them together into a single image. This is why the light from a TV
screen seems to flicker in a dark room -- the picture really is flickering back and
forth between the two half-frames.
This is a fairly crude method of developing a video image
that dates back to the early ‘50s. Most computer screens, for example, don't employ
NTSC. Not only do they divide the three color components into discrete signals (RGB), they
use progressive scanning, which does away with alternating (interlaced)
half-frames.
After years of debate (which still hasn’t been
completely settled), the Federal Communications Commission (FCC) has mandated a changeover
from analog to digital broadcasting (tentatively slated for January 1, 2007). The Advanced
Television Standards Committee (ATSC) advocates an over-the-air signal
transmission protocol, called Table 3, and manufacturers are producing DTV-ready sets,
which are called high-definition televisions (HDTVs).
The definition of an HDTV, according to the Consumer
Electronics Association (CEA), is one which can: 1) receive ATSC terrestrial
digital transmissions and decode all ATSC Table 3 video formats, 2) display vertical
scanning lines of at least 720 progressive (720p) or 1080 interlaced (1080i), 3) display
an image in a 16:9 (width:height) aspect ratio, and 4) receive and then reproduce or
output Dolby Digital audio.
There is finally some HDTV programming available, and most
manufacturers are producing HDTV sets -- or at least HDTV-ready sets, which require
separate set-top boxes (STBs) -- to actually process HDTV signals, but we currently seem
to be stuck in a battle between manufacturers and broadcasters in which each party is
blaming the other for the slowness of the rollout to HDTV. Manufacturers say sales are
sluggish because of the paucity of true HDTV programming, while broadcasters are reluctant
to spend money on upgrading to HDTV transmission before a certain number of HDTV-equipped
households exist.
But there is HDTV out there if you want it bad
enough. You'll either need to live within line-of-sight of a broadcaster transmitting HDTV
(and use an external HDTV antenna) or subscribe to one of the small-dish satellite TV
services, which offer HDTV programming (which requires a special converter box). The
recent winter Olympics were broadcast in HDTV and it seems as though everyone who got to
experience the HDTV coverage now wants as much hi-def sports coverage as possible.
There is the question of cost, however. A really good HDTV
system can set you back $10,000 or more. You can buy 32" direct-view or 40"
rear-projection TVs for as little as $2000, but the larger units go up in price at a rapid
pace. Add to that $500-1500 for a STB or satellite STB and another $500 for an antenna and
it starts adding up fast.
Many people have solved the problem by buying HDTV-ready
monitors and putting off the STB until they have more OTA and satellite options to choose
from.
Whether you choose HDTV right now, adopt a wait-and-see
attitude, or compromise with an HDTV-ready television, you'll get to choose from a wide
variety of options. They all fall into one of the following categories: Direct View (CRT
or PDP displays), Rear-Projection TVs (RPTVs), or Front-Screen Projectors.
Brief descriptions of these technologies are outlined
below:
- CRT: The most conventional form of TV uses
a Cathode Ray Tube (CRT). CRT TVs range in screen size from 13 inches to about 40
inches (measured on the diagonal) and range in price from around $280 to $4000.
- PDP: A flat-screen direct-view television,
the Plasma Display Panel (PDP) is thinner and lighter than a CRT. Because CRTs
create their pictures by stimulating phosphor cells with an electron beam, they need to be
deep boxes so the electron-firing gun can reach the entire screen. Plasma panels stimulate
phosphor cells individually with electrodes. The panel's focus remains uniform and there
are no distorted areas caused by curved screens or hot spots (unusually bright areas). The
result is a bright, richly colored, clearly detailed HDTV-ready picture in a frame shallow
enough to hang directly on the wall -- PDPs range from about four-to six-inches deep. They
don’t come cheap, however; expect to pay upwards of 8 grand.
- RPTV: Rear-Projection TVs (RPTV)
projects an image directly on the inside of the screen, enlarging the picture with a
series of mirrors and lenses. These televisions are large -- sometimes too big to fit
through conventionally sized doors (always measure before ordering!), but they can boast
screen sizes of 60 inches or more -- far larger than is possible with a direct-view
screen. Prices range from around $2000 to around $7500.
- Front-Screen Projectors: At the top of the
home-video heap are the Front-Screen Projectors, which come in three main types: Liquid
Crystal Display (LCD), Cathode Ray Tube (CRT), and Digital Light
Processing (DLP). They can deliver a picture size anywhere from a 60" diagonal to
a 10’ diagonal, but they require dedicated screens and a low-ambient-light
environment. However, if you want to experience the same vivid picture quality at home
that you get at an Academy-certified theater, they're the obvious choice. Affordable
data-grade DLP projectors can cost as little as $2500; state-of-the-art CRT projectors can
cost as much as $40,000.
Next time we'll take an in-depth look at HDTV and its
future.
...Wes Phillips
wes@onhometheater.com
|
