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)
I consulted the revision checklist.
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>.