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- Introduction to
HDTV -
Introduction
High Definition Television refers to a television broadcast with a considerably higher resolution than standard definition broadcasts currently allow. Today's high definition broadcasts, also known as HDTV are all digital, allowing for both higher resolution and also digital compression, both of which are not available with traditional analog broadcasts.
To fully receive high definition broadcasts with the maximum picture resolution, you require a HDTV compatible television that supports HDTV's native 16:9 aspect ratio. The high resolution picture, (1920X1080 pixels or 1280X720) allows a much greater detail than standard broadcasts allow.
The earliest known working HDTV system came from Japan, which began broadcasting analog high definition signals in the early 1990's using an interlaced 1035i resolution scheme which had engineering roots stretching back to the very early 1980's. This was referred to as the Japanese MUSE system. This system was later replaced by a digital high definition scheme.
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Sony's first high definition television developed in 1993 for the Japanese analog MUSE HDTV system.
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The mid 1980's also saw the emergence of uncompressed high definition broadcasts in Europe. The early standard was known as HD-MAC and although it was mandated for use, it never caught onto the main stream due to high transmission costs and other disadvantages. The standard was abandoned in 1993 by the European Union to make way for the more advantageous DVB (Digital Video Broadcast) system, which allowed bother digital standard definition as well as high definition digital broadcasts.
Engineering a high definition system in the United States began in the late 1980's. The first high definition television systems came onto the U.S. market in 1998, with the first digital high definition television broadcasts beginning in November of 1998. The Federal Communication Commission (FCC) has aggressively pushed for total adoption of digital standards and has made a number of mandates that all full power television broadcast stations must convert to digital broadcasts by 2007. The FCC has also mandated that 50% of all 36"+ televisions must be HDTV capable by 2004, with total inclusion by late 2005. At this time, analog off air broadcasts will cease to exist and the FCC will be able to resell the freed up spectrum to other industries. When this switch over happens, people receiving off air television signals will need to purchase a digital receiver to continue receiving off air broadcasts using analog televisions or purchase a digital capable television. The FCC's mandate covers only digital broadcasts, not high definition, so many of the analog stations will conceivably switch to a digital standard definition broadcast as it offers a lower transmission cost. To date, high definition in the U.S. has been fairly widely adopted, with thousands of digital off air broadcasts available across the nation, with more being added every day. Additionally, digital direct to home satellite broadcasters, such as Directv and Dish Network, which already broadcast a digital standard definition signal have limited offering of high definition signals to their subscribers. Most major cable vision companies also offer their customers a limited amount of high definition and standard definition signals.
In Canada, adoption of the high definition and digital standards has progressed at a much slower pace. Unlike the U.S., which has a digital adoption mandate, Canada's broadcasting system has progressed more slowly as it is currently voluntary. The CBC was the first in Canada to offer high definition broadcasts in 2003. To date, there is little more than a dozen off air digital high definition broadcasts available across Canada, mostly centered in large centers in Toronto, Ontario and Vancouver, British Columbia. Canada's 2 direct to home digital satellite companies, Star Choice and Bell Expressvu, have limited offerings of high definition broadcasts as well as the major Canadian cable broadcasters, such as Rogers, Shaw and few others.
HDTV or High Definition
Television has been capturing a lot of attention for the
past several years. In its infancy, a person wishing to receive
television programming in high definition needed
to spend tens of thousands of dollars. In the past couple of
years however many mainstream television and video manufacturers
have brought the price down substantially. Today, most mid-range
to high end wide screen televisions and rear projection systems
have HDTV capability. While most system available today are sold
"HDTV capable" or "HDTV Ready", meaning they still require an
external HDTV decoder, however some high end models, such as
LCD's and Plasma televisions have a built in decoder for
reception of off the air HDTV broadcasts. By 2006, nearly all new
televisions sold must be capable of receiving digital
broadcasts.
One of HDTV appeals is that it offers a much more lifelike
picture and digital sound quality. As it offers more than double
the resolution compared to regular television broadcasts, it
produces a much great degree of clarity and picture quality. The
highest HDTV format delivers approximately 2 million pixels, more
than 10 times the amount on standard analog broadcasts. Standard
analog television broadcasts in North America are limited to 525
lines of resolution, of which 45 lines are lost in synchronizing
the television to the NTSC video signal. This leaves 480 visible
lines of resolution, approximately 210 000 pixels.
Digital Television Formats
There are currently 18 different North American digital
television (DTV) formats, of which 6 are distinct HDTV
formats;
- HDTV Format 16:9 Aspect
Ratio
- High Definition 1080p -1920x1080 pixels
progressive, 24 frames per second
- High Definition 1080p -1920x1080 pixels
progressive, 30 frames per second
- High Definition 1080i -1920x1080 pixels
interlaced, 60 frames per second
- High Definition 720p -1280x720 pixels
progressive, 24 frames per second
- High Definition 720p -1280x720 pixels
progressive, 30 frames per second
- High Definition 720p -1280x720 pixels
progressive, 60 frames per second
There are also 5 formats of 480 lines of resolution progressive,
known as EDTV (Enhanced Definition Television),
which offers less that HDTV, but more than SDTV. EDTV use a 4:3
aspect ratio. The 5 formats of EDTV are;
- EDTV Format 4:3 Aspect
Ratio
- 480p -704x480 pixels progressive, 30 frames
per second
- 480p -704x480 pixels progressive, 60 frames
per second
- 480p -640x480 pixels progressive, 24 frames
per second
- 480p -640x480 pixels progressive, 30 frames
per second
- 480p -640x480 pixels progressive, 60 frames
per second
In addition, there are 3 formats of 480 lines of resolution
interlaced known as SDTV (Standard Definition
Television), which offers a much improved picture quality than
that of standard television, while less that that of HDTV and
EDTV. SDTV picture quality is comparable to that delivered from
digital satellite systems. Most analog NTSC programming that is
up-converted to digital is delivered in the final SDTV format.
The eight formats of SDTV are;
The terms interlaced and
progressive refer to the scanning system. The
interlaced format shows every odd line with one scan of the
screen and then follows with the even lines in the second scan.
Since there are 30 frames shown per second, the screen is only
able to show one frame every 60th of a second. On larger screen
sets, this translates into a noticable flicker effect. The
progressive format shows the entire picture, all lines in one
showing, every 60th of a second. This provides a smoother
picture, but uses a higher amount of bandwidth. The more frames
per second, the better the picture quality.
To put things into perspective, standard analog televisions
are capable of receiving a maximum of 480 lines of resolution,
however what you actually receive will be limited to your source
material and connections to your television. For example, a DVD
player connected to your television via composite video cable can
deliver only 330 lines of resolution, using an S-video connection
can deliver up to 400 lines of resolution. The same DVD player
can deliver nearly 500 lines if a composite video connection is
utilized. A standard VHS VCR delivers only 225 lines, while a
SVHS VCR delivers up to 400 lines and a standard analog
television broadcast delivers only 330 lines of resolution.
The aspect ratio of a television refers to its screen width
relative to its height. Conventional televisions use a 4:3 aspect
ratio, giving them a squarish appearance. Wide screen televisions
use a 16:9 aspect ratio, meaning they are nearly twice as wide as
they are high.
Sources of High Definition Television Programming
Today, high definition programming comes from three sources,
off the air, which requires a HDTV decoder & HDTV antenna,
cablevision, which requires a cable HDTV decoder, and satellite,
which requires a special satellite decoder box or integrated
satellite HDTV receiver.
Off the Air
In the early days of HDTV, it was very rare to be able to
receive a high definition off the air broadcasts, so consumers
had to turn to satellite or cablevision for a taste of high
definition. Today in the USA, there are now a wide selection of
off the air local channel broadcasts nation-wide in most major
cities with more being added all the time, primarily due to a FCC
mandate to begin phasing out standard analog broadcasts in favor
of digital ones by 2006. Having ones local channels broadcast in
high definition will also help to entice people to watch off the
air programming, as opposed to paying to receive it from a
satellite or cable provider. When 2006 approaches and analog
broadcasts are phased out, consumers in the USA will either need
to upgrade to a digital capable television or invest in a HDTV
set top box that receives and converts the digital signals to
analog to continue receiving their television programming on
their analog televisions.
In order to receive off the air programming, you will need a
HDTV capable antenna and a high definition set top receiver. For maximum
picture quality and resolution, you will need a HDTV capable
television that will be able to take full advantage of the 1080
lines of resolution. You will be able to receive the high
definition signals on a regular analog television using a HDTV
receiver, however your picture quality will be limited to near
DVD quality. As part of the FCC digital mandate, most local
networks (ABC,NBC,CBS,PBS) began broadcasting digital signals in
2003. Additionally there are also a multitude of other networks
such as PBS and FOX that are currently or will be broadcasting
digital programming in the near future.
Off the air HDTV signals operates on an eight level vestigial
sideband (VSB) technique that utilizes UHF channels. Unlike
analog off the air reception, with digital signals, you will
either receive the signal or you won't. There are no "fringe
areas" with snowy picture. However, homes located outside of
urban areas will need more powerful outdoor antennas to receive
the signal at an adequate strength to permit reception. Since
there are no restrictions on which DTV format broadcasters can
use, you can expect a difference in picture quality and
resolution between broadcasters as some will be using the various
HDTV formats while others will use the SDTV format. Regardless of
the format used however you can expect a much great degree of
picture clarity compared to analog television.
In Canada, there are now a limited selection of off the air
HDTV channels available in a number of major urban cities such as
Vancouver and Toronto and surrounding areas with many more in
most major Canadian cities expected by the end of 2004. By 2006,
most major Canadian cities and surrounding areas should offer a
good selection of high definition programming. If you are a Canadian living
near the U.S. border, you may also be able to receive off the air
U.S. HDTV signals as well.
More information on off the air receivers and antennas can be
found on our High Definition
Buyers Guide.
Satellite High Definition Providers
Direct to home satellite providers are also a means of
obtaining HDTV programming. DTH satellite providers are already
broadcasting in digital format, however their standard set top
receivers must convert the digital signal into analog for viewing
on standard televisions which has a negative effect on picture
quality. You will still receive a better picture in most cases
than an analog equivalent, however not nearly as good as you
would if the digital-analog conversion did not take place.
In order to receive HDTV signals off satellite, you will need
a special HDTV IRD or receiver, which is capable of receiving
both standard and high definition programming. As an alternative,
some HDTV decoders for receiving off the air broadcasts are also
capable of interfacing with a standard satellite IRD allowing
HDTV reception.
At the moment, most satellite providers offer a limited amount
of HDTV programming in the range of 7-10 channels. The exception
to this is the U.S. satellite provider, VOOM which based is
business model on HDTV and is currently providing up to 40 HDTV
channels in addition to standard definition ones.
U.S. Satellite HDTV Programming
Canadian Satellite HDTV Providers
More information on satellite HDTV products is available on our
HDTV
buyers guide
Cable Vision High Definition Providers
In addition to off the air and satellite providers, your local
cable provider should also have a limited selection of HDTV
channels. More cable providers currently have less than 10 HDTV
channels. Some smaller regional cable providers have not yet
added HDTV to their programming lineup. You should check with
your local cable provider for an up to date listing of HDTV
programming.
In order to receive HDTV via cable, you will need a special
HDTV receiver which can be purchased or rented from your cable
provider. This will allow you to receive and send the digital
signal to both digital televisions and also analog
televisions.
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09/19/2007 12:08 AM
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