Digital television is a new way of broadcasting television signals. It is different from today’s way of doing it, known as ‘analog.’ In analog broadcasting the signal is in the form of a continuous wave form whereas a digital signal is in the form of discrete bits of information.
Digital television is better than analog for several reasons.
Analog and digital television differ in the way the information is carried from the source to the receiver. In simple terms, in analog broadcasting the signal is in the form of a continuous wave, whereas digital is in the form of discrete bits of information.
For viewers, digital television will mean clearer, sharper pictures and a reduction in the interference and ghosting that currently affect many viewers in built-up areas or hilly terrain.
Other advantages of digital television will include cinema quality images with widescreen pictures and the added benefit of surround sound.
The change to digital television will also enable viewers to receive datacasting and enhanced television services which may include subtitles, captioning, further information on programming and a choice of viewing angles.
Digital television is a far more efficient and flexible transmission system than the current analog system. It allows broadcasters to offer viewers a range of new and different services. Digital television features can include:
Free-to-air broadcasters will simulcast (ie, broadcast both analog and digital signals), so viewers will continue to be able to use current analog television sets to receive broadcasts. And, beyond the end of simulcasting, the addition of a digital-to-analog converter in the form of a set-top box will allow viewers to continue to receive digital transmissions with their analog sets.
Viewers using set top boxes will be able to receive other features of digital, such as additional program streams. Because most existing analog sets have a 4x3 screen format (shape), using a digital set top box with a 4x3 analog television set may affect the way widescreen transmissions are displayed.
Use of a widescreen analog display will enhance the digital experience. The full picture quality benefits of digital television, including High Definition television (HDTV), will require a widescreen digital receiver that is capable of receiving and displaying a HDTV signal.
Viewers will be able to access most of the enhanced features of the digital signal, including clearer pictures and improved reception in built-up areas. The set-top box, however, will not cause an analog television to display a high definition picture. With the addition of a set-top box, an analog television will either display the images in the current 4:3 aspect ratio (width relative to height) or in a widescreen 16:9 ratio with the addition of black bands above and below the image.
Digital channels have been allotted in such a way as to minimise costs to consumers. When allotting channels for a market, particular attention was given to ensuring that, as far as possible, consumers will not be required to purchase an additional receive antenna.
In the majority of cases, existing antennas, which are appropriate for receiving the local analog television services, are maintained in good condition and are properly installed, will be adequate to receive digital television transmissions.
A set-top box for digital television receives and decodes digital transmissions into a form suitable for display on analog television sets or other display devices, eg computer monitors or projection screens. Analog television sets cannot display digital transmissions on their screens without being connected to such a set-top box converter.
The capability of a set top box will depend upon its specifications.
A set top box, when connected to an analog television set, will usually give viewers an improved signal, SDTV-equivalent picture quality and multichannelling. Some set top boxes may also provide viewers with datacasting services and video, audio and data enhancements.
Set top boxes capable of receiving and displaying a HDTV signal may not be available initially.
Set top boxes can provide a picture output to either analog or digital screen displays.
This is a television set which contains all the components necessary to receive and display digital transmissions. Integrated digital television receivers will generally be distinguished by wide screens, high level audio capability and high resolution displays. They will not require a set top box.
Standard Definition television (SDTV) is digital television with improved reception capability when compared to the existing analog service.
SDTV will be in widescreen format, provide enhancements and multichannelling, and eliminate ghosting and other errors found in analog transmissions. The aspect ratio of SDTV is either 4:3 or 16:9.
High Definition television is the premium version of digital television, offering picture and sound quality which is much better than today's analog television. In fact, it is closer to cinema quality than what we are used to as television. The reason is that it offers up to twice the vertical and horizontal resolution of a traditional analog (PAL) signal. The higher resolution picture is particularly suited to large screen television displays.
This means that the benefits of HDTV are particularly noticeable on larger screen sets and when using projection equipment. HDTV will be in widescreen format and provide cinema-quality viewing with Dolby surround sound.
HDTV provides a sharper picture than SDTV because there are more lines and pixel's on the screen. These make the picture look sharper and more detailed to a viewer.
However, perceptions of 'quality', as seen by the viewer, are affected by other factors besides sharpness, such as:
On a good quality television set, of the size typically seen in Australian family rooms, an SDTV receiver is capable of providing very high quality television experience.
Because a digital signal can carry much more data than an analog signal, more than one channel of television programs can be broadcast in SDTV at the same time. This is known as multichannelling.
Viewers of digital television will have a wide choice of 'enhancements' to regular programming.
Enhancements are separate channels of video, data or audio, which are related to the program on the primary channel.
Sporting events will offer the choice of different camera angles, action replays, player profiles or other information. Across a range of programming, digital viewers will have a choice to select more information related to the regular program - product information, recipes, news background and much more.
In addition, if a sports event overlaps with the news, digital viewers may be offered the opportunity to watch the regularly scheduled news bulletin or the completion of the event on a separate channel.
Because a digital signal can carry much more data than an analog signal, broadcasters and other licence holders will have the option to provide information services to viewers, in addition to regular program channels. This is known as datacasting.