Digital TV

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What is a digital television set top box receiver?

A digital television set top box receives and decodes digital terrestrial television transmissions into a form suitable for display on analogue television sets, display panels or other screen display devices such as computer monitors or projectors.

Analogue television sets currently in use in Australia cannot display digital transmissions on their screens without being connected to such a digital television set top box receiver

What does a digital television set top box do?

The capability of a digital television set top box will depend upon its specifications.

A digital television set top box, when connected to a 4:3 analog television set, will usually give viewers an improved signal, better picture quality and multichannelling. Some set-top boxes may also provide viewers with datacasting services and video, audio and data enhancements.

What is an integrated digital television?

This is a television set with in-built digital television tuner providing the capability to receive and display digital television transmissions.

Integrated digital televisions (iDTV) generally incorporate a high quality widescreen display and a high-level audio capability with appropriate audio/video connectors. An iDTV does not require a digital television set top box to receive digital television though an additional set top box could be connected to provide recording or other functionality.

What are Standard Definition (SD) pictures?

Standard Definition picture quality is superior to that obtained from analogue television broadcasts traditionally viewed on 4:3 television sets, and is 'ghost free' and in widescreen format.

The Standard Definition picture resolution is 576 lines x 720 active pixels @ 50Hz interlaced (576i).

The Federal Government requires broadcasters to provide a digital Standard Definition signal at all times, even when High Definition programs are being broadcast. This is to ensure that viewers with Standard Definition receivers will always be able to receive a digital television service even when the higher quality High Definition television signal is being transmitted.

Why are digital TV pictures sharper than with analogue TV?

Analogue television can suffer from multipath interference, which results in a 'ghosted' picture on your screen.

Free to view digital TV is not affected by multipath interference and picture 'flutter'. So the digital result is a sharper, cleaner and clearer picture. In areas of low signal strength, viewers of analogue television may experience 'snowy' pictures. Without adequate signal strength being delivered to a digital set top box, digital television may not improve the viewing experience compared to analogue. The digital TV picture and sound may be further affected by poor quality cables and connectors. It is recommended to use quality F-type connectors and quad shielded coax cables to ensure optimum picture and sound performance.

What are High Definition (HD) pictures?

High Definition television broadcast pictures have image resolution which is superior to Standard Definition pictures and to the existing analog television broadcast offering a quality improvement of up to three times the improvement in detail.

Australian broadcasters are currently using four different levels of high definition:

  • 1920 active pixels x 1080 lines @ 50Hz interlaced
  • 1440 active pixels x 1080 lines @ 50Hz interlaced
  • 1280 active pixels x 720 lines @ 50Hz progressive
  • 720 active pixels x 576 lines @ 50Hz progressive

The benefits of High Definition pictures at the highest resolution are particularly noticeable on larger screen sets and when using projection equipment.

High Definition pictures are also ghost free and in widescreen format. When viewed on an High Definition capable television ;screen the viewer can enjoy cinema-quality viewing with Dolby Digital sound (where available with some High Definition programming).

Commercial free to air broadcasters are required to transmit a minimum of 1040 hours of 'native' High Definition programming (including advertisements) each year. In regional areas this requirement applies two years after the commencement of digital TV transmissions in an area. Programs transmitted in High Definition will also be simultaneously broadcast in Standard Definition (also known as the simulcast).

Is a new antenna required to receive digital television?

Generally viewers will have good digital reception of free to view digital TV from their existing antenna provided it is relatively new, is in good condition and is connected with good quality coaxial antenna cabling.

If the viewer currently receives good analog TV reception there should be no reason to buy a new antenna unless and until it proves to be inadequate except in some cases it may not be suitable for Channel 11 + 12.

If your free to view digital television reception is not adequate you may need to replace your existing antenna and possibly the cables from the antenna to the wall socket.

What are current antenna installation anomalies?

Now that free to view digital television is well under way in Australia, we are gaining experience in making digital terrestrial television work in the installed antenna base.

Experienced television antenna installers and broadcasters are able to identify some installation anomalies already present in domestic and commercial premises.

These anomalies usually involve the use of installation solutions in inappropriate ways. The identified anomalies include:

  • The use of poor quality cabling, connectors and associated components
  • The inappropriate use of filters - stopping distribution of additional channels while attempting to reduce interference to analog
  • Failing to reduce Band I (Ch 2) and other channel levels causing overloading in amplifiers and TV tuners
  • Failing to reduce FM (Band II) signals causing interference to analog channels in Band III
  • The use of distribution amplifiers in lieu of masthead amplifiers
  • The use of masthead amplifiers in lieu of distribution amplifiers
  • Overloading of amplifiers - inadequate derating of output level and gain
  • In general carrying out installations without consideration of requirements as set out in Australian standards (AS 1367) for analog TV

Is audio better on digital television than on analogue?

Yes. Australian television programming has traditionally been broadcast with FM stereo sound.

Digital television will be transmitted with MPEG digital stereo sound (the equivalent of CD quality) and/or Dolby Digital Sound (2, 4 or 5 channels) where available, thereby providing markedly superior audio services.

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