DIGITAL TELEVSION: THE ENHANCEMENT OF TELEVISION
The Federal Communications Commission states, “DTV [Digital
Television] is a new type of broadcasting technology that will transform
television as we now know it” (2008). DTV is a broad term that includes high
definition TV (HDTV), standard definition TV (SDTV), data casting, multicasting
and interactivity. Today, most TV broadcasters in USA transmit both analog and
digital TV signals. However, all full power TV stations will be required to
change their broadcasting into an all digital transmission on February 17,
2009. The transition into an all digital
broadcast will increase transmission efficiency enabling broadcasters to
transmit high quality images, digitally enhanced sound, and other data ("Digital
Television (Dtv) Tomorrow's Tv
Today! ").
At present, broadcasters transmit analog TV signals by using radio
waves. Analog TV consists of PAL, NTSC, and SECAM system televisions. DTV signals
are different from analog TV signals. DTV signals are coded in 0’s and 1’s, and
they are similar to binary computer language. Both analog and digital TV signals
are transmitted on a broadcast spectrum of a specific bandwidth. The size of
the broadcast spectrum is limited and only changes by adjusting the size of the
bandwidth. DTV signals occupy less space on the broadcast spectrum, which allows
broadcasters to transmit more information using the same amount of bandwidth.
Imagine the broadcast spectrum to be an interstate highway. The size or width
of a highway can only increase by reconstruction, similarly, the size of the
broadcast spectrum only increases by changing the bandwidth. On this interstate
highway analog signals would represent large trucks, and digital signals would
be motor bikes. The use of digital signals, over analog signals, would free up space
on the spectrum, or highway, and make transmission more efficient. Broadcasters
will be able to use this extra space to transmit more information and other
data. This efficient use of bandwidth space is called bandwidth squeeze. Bandwidth
squeeze, and the nature of digital signals in DTV, will provide DTV viewers
with enhanced visual images, improved sound quality, and better information. (Commission; Cringley).
Enhanced Visual
Experience: HDTV images are sharper and clearer than analog TV images. SDTV
provides images that are similar to analog TV; however, most DTV’s in the U.S.
are HDTVs. Bandwidth squeeze, the nature of digital signals, and the physical
design of HDTV’s all contribute to create an enhanced visual experience. Bandwidth
squeeze allows broadcasters to transmit more visual data which results in an improved
picture quality. An image transmitted in a digital format will be exactly the
same at both the source and the receiving TV; however, analog TV images are
weaker than the original broadcasted image. Both analog and digital TV signals grow
weaker as they distance from their source. The strength of the analog signal
that reaches the TV is directly proportional to the image quality, a weaker
signal results in a poorer picture. Examples of analog signal deterioration are
snowy and hazy TV images. DTV images remain constant, from source to recipient,
because of the nature of digital signals. As long as a digital signal is
detected, regardless of its strength, the image displayed will be the same as
the one that was transmitted. The exact image of a house sent from the
broadcaster will display on the viewer’s TV, regardless of how far away the
viewer is located from the broadcasting station. However, digital signals suffer
from the cliff effect in which the data is either perfect or nonexistent. The cliff effect is
depicted when a cell phone call is suddenly ‘dropped’ as a user enters a tunnel,
or a location, where there is no signal (Cringley).
Digital signals received on HDTVs provide sharper, and clearer, TV
images than those seen on analog TVs. The physical design of a HDTV also allows
HDTV images to be better than NTSC image. All TV screens use pixels which are,”…the
smallest resolvable small rectangular area of an image…” (Cringley)
In a painting, that uses the stripling technique, a multitude of individual
dots create a larger picture when viewed from a distance. A dot in the painting
would represent a pixel on a TV screen. HDTV pixels are smaller, squarer, and closer
together than NTSC pixels. Four and a half HDTV pixels will fit in place of one
NTSC pixel, resulting in four times more detail for the same area. HDTV images are
better than what the human eye actually sees. If a viewer compared the image of
a flower, as seen by the naked eye, to the same flower on HDTV, the HDTV image would
seem magnified (Cringley).
HDTV uses rectangular screens which are similar to movie theater
screens. HDTV’s have screens with vertical to horizontal ratios of 9 to 16;
this compliments our sight lines by making it similar to the manner in which we
actually see. A car race viewed on HDTV will encompass more background images
on the right and left sides. The race would also appear magnified, and the viewer
will be able to discern the clothes worn by the spectators. HDTV images are
better than analog TV images because of the larger and clearer pictures. HDTV
images are further enhanced by high quality digital sound(Commission; Cringley).
Enhanced digital quality
sound: Bandwidth squeeze will also enable broadcasters
to transmit sound in the Dolby Digital/AC-3 audio encoding format. This is the
same sound quality heard in movie theaters. Traditional NTSC supports 2 channels
of stereo sound; however, HDTV will provide 5.1 channels of surround sound. The
5.1 channel sound consists of three sources of sound from the front, two from
the rear, and a subwoofer for impact. The subwoofer is the .1, in the 5.1
channels of sound. The 5.1 channels of sound will allow the audience to hear
sound from all directions. A viewer watching a nature program would hear
background sounds, such as birds chirping, from the rear speakers. The sudden
roar of a tiger would also be heard from the rear, however, the sound effect
would make the viewer jump and look behind. A video of a race car accelerating
will be accompanied by sound that travels, whereby, the engine noise of the race
car will start from the one direction and move to the opposite direction. The
5.1 channel sound system will enable viewers to hear sound from all directions
making it similar to ‘actual sound.’ Bandwidth squeeze will allow broadcasters
to transmit larger amounts of audio data; this would improve the quality of
sound. DTV sound will be similar to CD quality sound. The enhanced sound
quality, and the 5.1 channel sound effect, will bring the high resolution images
of HDTV to life. ("Digital
Television (Dtv) Tomorrow's Tv
Today! "; Cringley).
The enhanced audio, and video, effects in DTV will be furthered by
TV programs that are interactive and informative.
Enhanced information and
data: Bandwidth
squeeze enables digital transmission to go beyond audio and visual information.
The space that is saved on the broadcast spectrum can be used to transmit
digital data. Bandwidth squeeze will permit broadcasters to multicast, and data
cast, making DTV informative, and interactive.
Multicasting will allow broadcasters to split their ‘bit streams,’
or single channels, into multiple channels. The space required to transmit an HDTV program
can be split into four SDTV channels that play simultaneously. Channel 5 could
be multicast and would have extensions such as: channel 5.1, channel 5.2,
channel 5.3 and channel 5.4. Channel 5, may have been a children’s program.
Bandwidth squeeze would allow channel 5 to be multicast into multiple
selections such as: channel 5.1 showing Sam reciting poetry, selection 5.2 would
depict Norma reciting poetry, selection 5.3 would be children’s learning games,
and selection 5.4 maybe sing along karaoke songs for children that can be
selected and replayed. ("Digital
Television (Dtv) Tomorrow's Tv
Today! "; Cringley).
Multicasting allows viewers to receive more information, related
to a channel or program, making DTV more informative than analog TV. Bandwidth
squeeze will also make DTV interactive, a feature not available on analog TVs.
Data casting will let broadcasters transmit multimedia games and
other interactive programs. Data casting
would also allow digital data to be transmitted enabling viewers to customize their
TV experience. The morning news could be customized to check for relevant
weather conditions, to follow the sports and the teams of a viewer’s interests,
and to attain information on specific news stories. Data casting will also
enable Electronic Program Guides (EPG) to be used on DTV. EPG would be similar
to a computerized ‘program guide.’ The EPG can be developed to be interactive,
thus, allowing viewers to select and view programs by preference. EPG could
also be enhanced to allow viewers to perform ‘program searches.’ A viewer could
locate a program, or related programs, by performing a key word search similar
to those on ‘Google.’ For example, inputting ‘cardiology’ into an interactive
EPG search would list multiple medical science programs. This, and other,
interactive data casting options are being developed to enhance the DTV
transition to extend TV beyond sound and image. ("Digital
Television (Dtv) Tomorrow's Tv
Today! "; Commission).
Data casting and multicasting are made possible by bandwidth
squeeze, which is a result of changing from an analog to digital transmission.
The transition into an all digital broadcast will also create additional
benefits for society. A complete digital
broadcast will free certain broadcast frequencies, which can be used for
essential public safety communications like police and fire emergencies. In
this manner DTV will not only benefit the viewer, with a better TV experience,
but will also benefit society. The complete enhancement of TV into DTV will
make February 19, 2007, a milestone in the history of TV. DTV will bring the
audio and visual effects of movie theaters into the homes of viewers, and completely
“…transform your [the viewer’s] TV experience…”(FCC,
2008)
IUSED ENDNOTE
I consulted the revision checklist.
Works Cited
Commission, Federal Communications. "Digital Television (Dtv)". Washington DC, 2008. Ed. FCC. (3/07/08): Webpage. FCC2008. <http://www.fcc.gov/dtv/>.
Cringley, Robert X. "Digital Tv: A Cringley Crash Course". 2008. webpage. Public Broadcasting Service. PBS. <http://www.pbs.org/opb/crashcourse/>.
"Digital Television (Dtv) Tomorrow's Tv Today! " Washington, 2008. webpage. Ed. Federal Communications Commission. (02/29/08): FCC2008. <http://www.dtv.gov/index.html>.