ShareDigital Television (DTV) and UEN TV
- Analog Television
- Digital Television (DTV)
- Over-the-air
- Screen Resolution
- Set-top Converter Box
- HD Ready / HD Monitor
- Multicasting
- Datacasting
- Additional Information
Analog Television
Since television was introduced to the public at the 1939 NY World’s Fair, TV broadcasters have used radio signals to transmit both pictures and sound using a continuously-variable electromagnetic waveform. This technology is referred to as analog broadcasting and is subject to interference and other types of signal degradation leading to static, “ghost” images, and other problems.
Digital Television (DTV)
While digital broadcasting still uses radio waves (although with a different frequency), pictures and sound are converted to a digital format, much like CDs and DVDs, before being broadcast. A digital tuner then takes this information and decodes it to yield pictures and sound. Using digital technology allows broadcasters to transmit and receive information much more accurately and efficiently and eliminates static, “ghost” images, and other signal problems. In addition, broadcasters can now embed multiple channels into their broadcast signal, allowing them to broadcast high-definition programming and multiple standard-definition programming streams.
Over-the-air
Most radio listeners and many television viewers use an antenna or “rabbit ears” to receive radio and television signals. This method, in contrast to receiving signals through a cable or satellite network, is referred to as “over-the-air.” Some television viewers use both over-the-air and cable or satellite delivery in their homes.
Screen Resolution
Because they have happened at about the same time, changes in television screen resolution often get confused with changes in broadcast technologies. As with computer monitors, a higher resolution television screen gives both more detail and a greater range of colors. Following is a short description of the screen resolutions and technologies currently used by televisions in the United States.
Standard Definition (SD)
This is the normal screen resolution for televisions over the past several decades. It consists of a 4x3 aspect ratio and a 480-interlaced (480i) resolution. Most programming is still filmed and broadcast in standard definition.
Enhanced Definition (ED)
Enhanced definition has become popular with DVDs; it consists of a slightly higher resolution (480-progressive, or 480p) and can be in either a 4x3 or a 16x9 aspect ratio. In addition, enhanced definition can include Dolby digital surround sound.
High Definition (HD)
High definition screens can display at least a 720p resolution, and in some cases a 1080i or 1080p resolution. They have a 16x9 aspect ration. High definition also can include Dolby digital surround sound. The 1080i and 1080p screens have the highest resolution currently on the market and are able to display a much greater level of detail and richness of color than any other screen. However, programs filmed at a lower resolution will lack the clarity and richness of programs filmed in high definition, even when viewed on an HD screen.
Interlaced Scan (i)
Televisions display a picture by scanning from left to right in rows. An interlaced scan fills in the even rows first, then goes back and fills in the odd rows (see “interlace” in Wikipedia for more information). An interlaced image lacks the ability to display high levels of detail.
Progressive Scan (p)
In a progressive scan, rows are still scanned from left to right, but no lines are skipped (see “progressive scan” in Wikipedia for more information). This method, while it requires a higher bandwidth, produces a much clearer and more detailed picture than interlacing.
Aspect Ratio
Aspect ratio refers to the ratio of a screen’s width to its height (see "aspect ratio (image)" in Wikipedia for more information). Hence, a 4x3 screen with a 40-inch width will have a 30-inch height, while a 16x9 screen with a 40-inch width will have a height of 22.5 inches. 16x9 is referred to as “widescreen” and has an aspect ratio similar to a movie screen.
Set-top Converter Box
With regard to DTV, a set-top box, or converter box, is a standalone digital tuner. It receives the digital signal from an antenna and decodes it into a format that an ordinary television can display. Apply for a converter box coupon here.
HD Ready / HD Monitor
Some televisions produced over the past several years have screens capable of displaying high-definition television programming, but they do not contain an integrated digital tuner. Such televisions are referred to as “HD Monitors” or “HD Ready.” A set-top converter box is needed when using such a television to view DTV programming.
Multicasting
Digital broadcasting allows television stations to transmit multiple standard definition and/or high definition channels simultaneously. This practice is called multicasting. A broadcaster who is multicasting uses sub-channels (e.g., 9-1 and 9-2) to transmit different programming.
Datacasting
Digital broadcasting also allows television stations to transmit data files using their broadcast signal. These data files can be received and decoded by various pieces of equipment, including some computers and televisions. Broadcasters can transmit information about shows, program schedules, and any other piece of relevant data. This technology can also be used to transmit computer files from the broadcast antenna to a receive site.