TV -- PRESENT & FUTURE
Buying a television used to be really easy. As recently as
the mid 1980s, once you'd settled on a 17, 21 or 25-inch screen, the big
decision was whether or not to splash out on luxury extras, like finger-touch
push-button tuning, remote control and if you were really flush, teletext. You
also got to choose between plastic, painted mockwood or genuine wood veneer cabinets.
Life was tough!
The arrival of stereo sound, satellite broadcasts and
plummeting VCR prices in the late 1980s changed all that. Almost overnight the
humble living-room telly was transformed from a passive display for four
terrestrial television channels into a sophisticated multimedia terminal.
Nowadays you have to know your way around terms like widescreen and flat
screen, analogue and digital, mono, stereo, pseudo, 3D, Dolby Pro Logic or
Dolby Digital surround, to name just a few. Then there are the widgets and
gadgets on offer, and that's before we get to the really technical stuff…
WIDESCREEN OR 4:3
Like it or not within the next five years the majority of
new TVs will have widescreen displays, but why? Time for a brief history
lesson. The TV screens we're all familiar with are is known as 'Academy' shape
with an aspect ratio of 4:3. In other words the screen is 4 units wide by 3
units deep, or almost square. The Academy shape was decided upon almost
arbitrarily by cinema pioneers in the late 19th century and adopted more or less
without question by the founding fathers of television in the 1920 and 30s.
However, in response to the growing success of TV in the 1950s Hollywood tried
to win back audiences by dabbling with various widescreen formats. Many
different styles were tried, from Cinemascope to Cinerama but the concept stuck
and the Academy screen virtually disappeared from cinemas by the 60s. Analogue
television technology is not very flexible and despite a few half-hearted
attempts to introduce widescreen systems during the 70s and 80s, the 4:3 shape
stuck, until now that is.
TVs with widescreen or 16:9 aspect ratio displays have been
in the shops for the past seven or eight years and analogue widescreen
technologies have been around for more than a decade but there's been precious
little to watch on them. Nevertheless
the changeover has begun and will accelerate as digital broadcasting gets
underway. Digital TV is very adaptable and it will makes it easier for
widescreen and 4:3 services to co-exist during the decade long changeover
A widescreen display is a more natural way of seeing things,
don't forget it's how we see the world. Widescreen displays have the same
general proportions as a cinema screen, so you can watch movies as they are
meant to be seen, without black borders at the top and bottom of the picture,
or with bits lopped off the sides. Since the early nineties most new made for
TV productions have been made in widescreen format, and that will be the norm
from now on.
Needless to say there are a few minus points. Widescreen TVs
are more expensive, but prices are falling rapidly. 4:3 pictures look a bit
weedy on a widescreen TV, especially on smaller models (sub 28-inches), when
the picture will actually be some 10-15% smaller than on an equivalent-sized
4:3 TV. So rule number one, when buying a widescreen TV, is to get the biggest
screen you can afford and comfortably fit into your home!
NICAM OR DOLBY PRO LOGIC?
Stereo sound came relatively late to British television but
it was worth the wait. Introduced in the late 1980s, Near Instantaneously
Companded Audio Multiplexing, (NICAM to its friends) uses digital technology to
provide near CD-quality stereo sound. Initially it was expensive but these days
NICAM sound adds little to the price. Unless you live alone and have only one
working ear you might as well have it. Do listen to a few sets first though,
performance varies a lot and some cheapo models sound only marginally better
than mono TVs.
NICAM also happens to be an efficient carrier for Dolby
Surround soundtracks. Dolby Surround is the name given to the Dolby Stereo
surround system originally developed for the cinema in the 1970s. Four sound
channels are cunningly entwined with a normal stereo soundtrack; there's the
usual right and left stereo channels, plus a centre front channel for dialogue
and a rear channel, used mainly for sound effects.
The two extra channels are extracted using a decoder, the
most popular being the active matrix or Dolby Pro Logic (DPL) type. Other types
of decoder are available but you can take it as read that none of them are as
good as pukka DPL. There are also a number of halfway-house solutions,
sometimes called 3D sound, that attempt to recreate a surround-sound effect
using only two stereo speakers, built into the TV. Again the effect is not as
good as proper DPL, with extra speakers behind the viewing position, even on
models that use a Dolby Pro Logic decoder to extract the extra information.
Some TVs have digital signal processing (DSP) systems in addition to, or
instead of DPL. These use a mixture of acoustic tricks to generate a range of
pseudo surround and spatial sound effects from mono or non-Dolby encoded
material. It's not the real thing but it can help to liven up old movies.
The most recent innovation is Dolby Digital also known as
AC-3. It's known in the trade as a 5.1 sound system and is another spin-off
from the movie industry. A 5.1 system like AC-3 has five independent CD quality
sound channels, (right, left, centre and stereo rear) plus a narrower bandwidth
channel carrying bass effects. Dolby Digital is the preferred standard for DVD
and similar 5.1 systems will be used by digital TV services from satellite and
terrestrial sources. So far only Toshiba have launched TVs with built-in Dolby
Digital sound systems, but it's a feature we can expect to see a lot more of,
as DVD players and disc fall in price. There is still some confusion over the
sound schemes that will be used by digital satellite and terrestrial
broadcasters, On Digital (formerly British Digital Broadcasting) say they won't
be using 5.1 channel sound, BSKYB who have the satellite franchise remain
vague, but do not rule it out.
IMPROVING THE PICTURE
TV manufacturers continually strive to improve the quality
of the pictures we see on our TV screens, though be aware of marketing hype.
One brand's super whizzo picture enhancement system may be a standard,
unannounced feature on another maker's TV range. That's why it's important to
use your eyes, not just to read feature lists and price tags, but to make side
by side comparisons.
The ultimate goal is of course high definition television
(HDTV), but for the moment at least all current systems have to work within the
constraints of the 625-line PAL system we use in the UK. The situation is
different in the US where digital TV is taking a slightly different path but
the bottom line is that digital TV pictures will not look significantly better
than current analogue TV -- if at all -- unless you happen to live in a fringe
However digital transmission systems do allow for an easy
upgrade path to HDTV, with pictures made up from more than 1000 lines. Because
of the narrowness and closeness of the lines, coupled with the increase in the
amount of detail in a HDTV image, it will look more like movie film. TV
manufacturers have devised many varied and ingenious ways to eliminate or
minimise so-called line structure from 625 line pictures. The best known, and
most successful method is known as line doubling. The gaps between the lines
are filled in with extra picture lines, generated by the TV (or decoder).
Clearly the extra lines cannot contain any additional picture information but
sophisticated digital processing circuitry can take an educated guess at what would
be on a dummy line, by looking at what is on the real picture lines either side
of it. This technique, known as interpolation, involves a lot of expensive
microchip circuitry, and it will be a while before it reaches the mass-market,
but keep an eye out for it, the effect is very impressive!
The other big problem with PAL pictures is flicker. It
doesn't seem to worry most people watching sub 28-inch screens, but for some it
can be very annoying. However, flicker becomes a lot more noticeable on larger
TVs, especially wide screen models, when it can become quite intrusive. The
problem is the PAL system has a screen refresh rate of 50Hz. The picture is made
up of two interlaced scans each lasting 1/25th of a second; thus a complete
picture is assembled on the screen 50 times a second. This figure was chosen
for a number of reasons -- mostly concerned with the way our eyes work --
though interestingly one of the deciding factors was the frequency of our
household mains supply. This is very carefully controlled and it provided early
set makers with a source of stable and reliable synchronisation signals.
(Incidentally, that is why the American NTSC system has a 60Hz refresh rate,
and as a consequence picture flicker is far less of a problem)
The most successful method of eliminating flicker is the
100Hz display. This works by doubling the picture refresh rate, so the picture
is scanned 100 times each second, putting it well outside the perception range
of our eyes. It works well, though it can cause motion artefacts, where rapid
movement can appear slightly jerky. This was a problem on early 100Hz sets but
improvements in digital processing have gradually lessened the effect. Even so,
if you're auditioning 100Hz sets it is always worth asking to see programmes or
tapes featuring sports or fast action sequences.
Picture tubes can have a big impact on image quality, though
the gap between the best and the worst is narrowing all the time. A lot of
people swear by the Sony Trinitron tube family, and it has to be said they are
generally very good indeed but do make sure you compare like with like, both in
terms of size and price range.
Noise can be a significant problem on analogue television
pictures (digital TV will suffer far less). It shows up in a variety of ways.
The most obvious one is the snowstorm effect, though it has to be said that a
lot of the time this is down to the quality of the TV signal or performance of
a source component (VCR, satellite receiver etc.), rather than the TV itself.
There is a noticeable difference in the way TVs deal with noisy signals, so pay
particular attention and make side by side comparisons on models in dealer
showrooms, especially if you live in a fringe reception area. If in doubt don't
be afraid to ask for a home trial.
Internally generated noise and poor noise rejection usually
shows up in highly saturated colours -- reds in particular -- and instead of a
solid clean colour, it may have a characteristic 'fizz'. Noise also robs a
picture of detail, sharp edges are less clearly defined, grass, leaves on a
tree, or hair, all looks muddy or indistinct. TVs with digital noise reduction
systems can also create artefacts, rapidly moving objects may appear to blur,
jerk or smear, so if you get the chance compare pictures with noise reduction
features, and any other picture enhancements switched on and off.
Teletext is one of the great, unsung heroes of television
technology. It was the first part of the broadcast signal to be digitised,
which is remarkable considering it was developed almost thirty years ago. The
first teletext broadcasts consisted of no more than a handful of pages,
containing news and television schedules -- even the clock was a later
addition. Today's magazines run to several thousand pages, since information is
sent sequentially -- i.e. one page at a time -- a particular page can take a
long time to appear.
To get around this problem broadcasters and set-makers have
adopted a number of strategies. The first is to send index pages, and those
that are likely to be accessed more often, more frequently in the sequence.
Most teletext equipped TVs have the facility to store frequently used pages
numbers, though this shouldn't be confused with page memory, where complete
pages are stored, for instantaneous access. This requires a great deal more
memory capacity and until recently it was an expensive option. As the price of
memory chips has fallen this feature is getting cheaper; the problem is to
decide which of the thousands of pages should be stored.
Fastext is one of the simplest methods for reduces the time
taken for a page to appear. Fastext is one of a number of refinements that goes
under the acronym FLOF (full level one features). Each page contains a number
of colour-coded links to related topics or key pages (news weather, TV guide
etc), assigned to coloured buttons on the remote handset. When the relevant
button is pressed the page number is automatically entered -- this alone saves
several seconds. To speed things still further some teletext decoder
automatically download and store linked pages in a page memory, so when the
fastext button is pressed the page instantly appears. A similar technique is
used to store all the pages following an index page.
Further improvements to teletext, including provision for
full colour, high quality photographic images and smooth graphics have been
included in the teletext technical specification for some time. UK broadcasters
dallied briefly with Level 2 teletext but wasn't adopted due to the big
increase in the amount of data, which drastically slows access time still
further. That's not a problem with digital broadcasting systems, which have far
greater data carrying capacity, and this has already spawned son-of-teletext,
in the shape of the Electronic Programme Guide (EPG), that will contain vastly
more detailed information, including high quality still pictures.
You have probably noticed that TVs have become a lot more
complicated in recent years. Some 'convenience' features can actually make your
life easier, though it has to be said that a lot of them are little more than
selling aids, designed to help dealers shift sets, or make one manufacturer's
product stand apart from the regiment of black boxes.
One newish feature that does earn its keep is auto
installation. Gone are the days when you had to twiddle and tweak little knobs,
or wait an age for the TV to tune itself in, then spend half an hour weeding
out all the fringe stations and minicab radio transmissions the TV locked on
to. Even so, some auto installation systems are not as easy as they purport to
be. If you're out shopping for a TV ask the salesperson to show you how it
works, and if they can't figure it out, without resorting to the manual or
expert help then give it a miss.
The extensive use of digital video processing microchips in
televisions has enabled manufacturers to tack on extra features at relatively
little cost. Some are patently pointless, for example, what possible use is a
freeze-frame mode on a TV? Picture zoom also falls into that category, but it
looks great in the shop. A few years ago there was a brief spate of sets with
digital strobe effect (a jerky picture), mosaic (a picture made up of coloured
blocks) but they disappeared almost as quickly as they came. Picture-in-picture
or PIP is a more useful extra, though it only really makes sense if the TV is
fitted with twin-tuners -- so you can watch two channels at once -- or the TV
is connected to a VCR or satellite receiver (by SCART AV cable). TVs with PIP
(or POP, picture outside of picture, in the case of some widescreen models)
often have a channel scan facility. This generates a display of miniature
sub-screens, showing a still image captured from each channel and AV input in
turn. It's clever and visually dramatic, but usually a whole lot slower than
surfing with the channel up/down button on the remote.
Now that digital TV is upon us some manufacturers and
dealers have taken to plastering their tellies with stickers saying 'Digital
Ready' or 'Digital Compatible'. Don't be suckered, every PAL TV made since the
late 1960's is theoretically digital ready. Most set-top decoders will have
aerial sockets, so they work like a VCR or satellite receiver, though picture
quality won't be as good as a direct AV connection, using a SCART lead.
Artificial intelligence, fuzzy logic and automatic picture
controls pop up from time to time. Most TVs with this type of feature have a
small light sensor somewhere on the front panel, the idea is screen brightness
and contrast are automatically adjusted to suit room lighting conditions. It's
rarely satisfactory, people's tastes vary too much to allow for factory set
preferences and we suspect most of these systems are switched off after a few
Always give remote control handsets and on-screen display
systems a thorough road test. See how easy it is to get the TV into the
teletext mode, and then back again to a normal picture. How many button presses
does it take to select an external input, adjust the sound or picture? How easy
will it be to find buttons in subdued light and does it look like the labelling
on the buttons are going to rub off over time? These things are important!
If you have kids then some form of parental lock might come
in handy, though most systems are fairly easy to crack, especially if you leave
the instruction book lying around. Sleep timers that automatically switch the
TV off after a pre-determined period could be useful if you regularly fall
asleep in front of the TV. Systems that turn the TV off when the station you're
watching closes down for the night might have been okay a few years ago, but
they're next to useless nowadays with round the clock broadcasting…
TVs with multi-system displays that can cope with AV inputs
from NTSC or SECAM VCRs laserdisc and DVD players only make sense if you
already possess such devices. Unless you're a real movie buff, who regularly
uses that kind of hardware and software it's really not worth bothering about,
and certainly not worth paying any extra for.
Don't forget the sound features. Large, open-faced widely
set speakers are better than small squitty ones, firing though slots in the
side of the cabinet. It is better to have tone controls -- however rudimentary
-- than none at all, count sub-woofers, external speakers, (or connections for
same) and any visible signs that the designers have tried to improve the sound
quality as a bonus.
ROUND THE BACK
The backside of a late 1990s mid-market television contrasts
strongly with sets made a few years ago. As befits the modern living room TVs
wider role there has been a dramatic increase in the number of sockets. Until
the mid 1980s most TVs had a single aerial socket, and possibly a 21-pin SCART
connector, though they were by no means as common as they are today. The
coaxial aerial socket is still there, but SCART sockets have become a more or
less standard fitment, and a growing number of mid-market models have two,
One SCART is no longer sufficient since most TV owners now
have at least two AV source components in their living rooms. Satellite
receivers, laserdisc players, video game consoles, and camcorders have joined
the ubiquitous VCR, now there's DVD to contend with. It is possible to 'chain'
a TV and satellite receiver together, indeed it is a good idea if you want to
record satellite programmes, but the best advice is not to skimp on the SCARTs,
and treat two as an absolute minimum.
Whilst SCART connectors are a useful (if somewhat clumsy)
means of conveying audio, video and control signals they lack flexibility, and
are rarely if ever used on equipment sold outside the EU. Many TVs have
additional sockets, to simplify connection to other devices. Simple, push-fit
Phono connectors (aka RCA and Cinch) almost always handle line-level audio
signals. Phono connectors are also used for composite video signals, the
convention is to colour the socket and plugs yellow, whilst audio connections
are coloured red and black (or white). A few manufacturers also use Phonos for
speaker connection, two-pin DINs are also seen from time to time, though spring
terminals are more common.
SCART connectors on some TVs are also configured for S-Video
(aka Y/C or component video). However, most manufacturers now seem to prefer
the 4-pin mini DIN (or Hoshiden) connector. Since this is a video-only link, it
does mean additional cables are needed for the audio connections, so the
backsides of well-used TVs can end up looking a bit of a mess.
Several top-end tellies can display computer video signals
(VGA or SVGA standard), so don't be surprised if you come across a 15 pin D-Sub
socket on the back panel, the same as those used on PC monitors.
The new generation of digital televisions will doubtless
spawn a whole new series of weird and wonderful connectors. Leading the pack is
IEEE 1394 or FireWire, a 2-way high-speed serial data link. The currently
favoured style is the DV jack, a small rectangular shaped plug and socket, but
don't worry, as far as we're aware no TVs have them, yet!
THREE TOP TELLIES
The Toshiba 3787DB is quite simply the dog's dangly bits, a
truly wonderful 37-incher Dolby Pro Logic model costing the thick end of two
grand. It scores on all counts, picture quality is outstanding, and it has a
100Hz display, Dolby Digital sound and no less than 11 speakers to hear it
through. Okay, so it's not a 16:9 model, but with a screen that size it hardly
matters and it is as near future-proof as it's possible to be.
If you can't scrape together the readies for the big Tosh,
or you haven't the room, then how about this cutie from Philips? The 28PW6332
is a 28inch widescreen set costing just under £900. That's good value when you
consider it comes equipped with Dolby Pro Logic sound, a built-in subwoofer and
loads of display modes.
When it comes to out and out picture quality the one to beat
is the Sony KV-32FD1, at your local dealer now for just £2800. It's all down to
the newly developed FD Trinitron picture tube, which is the flattest CRT to
date. The picture is so sharp you could
cut yourself on it, the sound is okay too, though if you've got that much money
to spend, you'll want to use it with some serious audio kit!
Crystal ball gazing is notoriously risky when it comes to TV
technology. Industry pundits have been predicting the imminent arrival of the
flat, hang-on-the-wall video display for at least the last thirty years. True,
you can now buy 42-inch flat plasma-screen displays, but only if you've got around
£12,000 to spare, and don't mind putting up with a fairly ordinary picture.
They're getting better, and cheaper, but the CRT still has a few years left in
Plasma screens have the flat screen market pretty much to
themselves at the moment. Liquid crystal displays (LCD) showed promise for a
while but production problems increase, and commercial yields fall dramatically
once they get past 15 to 18 inches across. LCD screens certainly haven't gone
away, though, and they've carved out a useful niche as computer monitors, where
the thin screen is a great space saver on crowded desktops.
The technology to watch is LEP or light emitting plastic.
LEP displays are still very much at the development stage but the technology
holds a lot of promise. A LEP screen is thin and flexible -- the developers
even talk about being able to rolling them up. Another significant advantage is
they can be produced using relatively simple manufacturing processes; it's no
coincidence that the leading UK company in this area has teamed up with a
manufacturer of inkjet printers. Small
prototype single colour LEP screens have been publicly demonstrated, it remains
to be seen if they can be scaled up to a useable size, with a colour display.
We'll keep you posted.
Another display technology worth keeping an eye on is the
digital micro-mirror also known as micro mirror devices (MMDs), from Texas
instruments. They've been around for a few years and were developed for use
used in projection systems. If successful could make current LCD and
high-intensity CRT display systems a thing of the past. On the top surface of
the chip is a matrix of microscopic mirrors, each one can be individually
addressed, and wobbled slightly. Thus each micro-mirror is effectively a single
picture element or pixel, so when a beam of light is shone onto the chip the
resultant reflection will form a picture, when focused through a suitable lens.
A colour image can be built up using three MMDs -- one for each primary colour
-- and suitably designed optics and light sources.
3D remains the Holy Grail of video displays and over the
years there's been no shortage of ingenious systems. The usual problem concerns
the need to wear special glasses or visors; such systems are unlikely ever to
succeed for the simple reason that people won't put up with such an imposition.
Lenticular systems, which use multi-faceted screens, so the eye sees two images
simultaneously, show a lot of promise but the 3D effect dissolves requires the viewer
to hold their head quite still. If a workable system is developed you can be
sure we'll let you know, but don't hold your breath…
BOX COPY 1
HOW WIDESCREEN WORKS
One of the main reasons why widescreen TV has been so slow
to arrive has been the need to retain compatibility with existing 4:3 displays.
The simplest solution is to broadcast (or record) the material in a letterboxed
format, with black bars at the top and bottom of the screen. When shown on a
16:9 TV the image can be electronically inflated, so that it fills the screen.
Either way it's a compromise, the black bars are irritating for the 4:3 viewer
and picture quality suffers when the image is enlarged. Panning and scanning a
widescreen image is very unsatisfactory, everyone looses, action at the side of
the screen is lost and it looks really odd.
Anamorphic compression, where a widescreen image is stretched
vertically so it fits in the confines of a 4:3 display gets around the quality
issue. The zoom facility on a 16:9 TV returns the picture to its natural
proportions, without loss of detail, but distorted anamorphic pictures are simply
unacceptable to most 4:3 TV viewers.
For a short while a widescreen transmission system called PALplus
looked like it might take off. The additional information, needed to produce a
widescreen picture, (actually extra picture lines) are made invisible and contained
within narrow bands at the top and bottom of the picture. The reduction in
picture height on a 4:3 set is tolerable and there's no loss of quality when
shown on a PALplus widescreen TV. Channel 4 still show the occasional PALplus
programme or movie, but other broadcasters decided not to back the system and it
was effectively killed off by the development of digital TV.
Digital TV from terrestrial and satellite broadcasters will
be almost exclusively transmitted in 16:9 widescreen format. Digital set-top decoders
electronically re-configure the picture to suit the shape of the TV screen to
which they are connected. It will involve some losses for 4:3 viewers -- a
slice of the picture is lost from both sides of the screen, like pan and scan -- but with some suitable electronic sleight
of hand the disruption is deemed to be acceptable.
BOX COPY 2
WHY DO TV PICTURES NEED IMPROVING? Digital TV has a lot
going for it but be very wary of anyone who tells you the picture quality will
be better than existing analogue services. Digital signals are less susceptible
to interference and noise should be much less a problem, but the overall
display remains the same, namely 625 picture lines (actually only 575 are
visible on the screen, the others carry data signals, like teletext, and
control signals). In fact there is a possibility that some digital broadcasts
will not look as good as analogue channel, on a properly set-up TV. The data
rate of some digital channels will be reduced to quite low levels, in order to
squeeze more out of the system.
Back in the analogue domain the biggest influence on picture
quality is not screen size, the sophistication of the receiver circuitry or any
noise reduction widgets, it is signal strength. In other words, before you dash
out and blow a couple of grand on the latest widescreen wonder, spend a few
pounds on a new aerial, or having your satellite dish checked over.
BOX COPY 3
THE HISTORY OF TELETEXT
The BBC claim to have come up with the basic concepts of
teletext back in 1970, however they didn't tell anyone about it until 1972,
when they announced the development of CEEFAX (see facts). IBA engineers began
work on their system, called ORACLE in 1972 and they gave the first public
demonstration (broadcast from the Crystal Palace transmitter) in April 1973.
Both systems were subsequently integrated and by 1974 teletext had been adopted
as a world standard.
The concept is simple. Sending pages of static text and graphics,
as normal television images would eat up frequency bandwidth, moreover it
doesn't work very well. Detail is lost and a still TV image is ironically far
too unstable for fine text, which would be very difficult to read. The solution,
which BBC and IBA engineers came up with independently, was the first outing
for digital technology in television broadcasting. Instead of sending actual images,
teletext pages are generated internally inside the TV, using a character
generator or graphics chip. The design and makeup of each page is determined by
a stream of digital data, sent by the broadcaster on blank, unused picture
lines, within the 625-line TV signal.
First generation teletext TVs were horribly expensive; the
facility typically added between £100 to £150 to the price (remember that was
25 years ago, when £150 was worth something…). Most of the cost was due to the large
number of decoder and display microchips required; though teletext TVs also
needed sophisticated remote control systems. Hitherto remote control was a
luxury extra, and more often than not, capable of little more of channel change,
volume and on/off switching. At the time ultrasonic remote controls were the
norm, and it was only with some difficulty that systems were developed that
were able to cope with the extra commands needed for controlling a teletext decoder.
The development of infra-red control systems
in the late 70s and simpler decoders, using dedicated LSI (large-scale
integration) microchips eventually helped bring teletext TV prices down.
R. Maybury 1998 0508