Television Today
Most Australians are still watching broadcasts that use an analogue signal, although the popularity of digital television is growing with over a million Australian homes now having access to it.
Digital television started in Australia on 1 January 2001. Currently, all free-to-air stations in Australia are required by law to simulcast (that is, broadcast both analogue and digital signals). However, in the not-too-distant future, all television stations will be required by law to broadcast their channels using only the digital format, so as to free up the analogue signals for other uses, and move Australia into the next level of television broadcasting quality.
There are two common types of digital television transmissions – Standard Definition (SD) and High Definition (HD).
This illustrates how High Definition television gives a sharper image quality (four times the resolution) than Standard Definition television.
Source: Erstellt von mir, Andreas -horn- Hornig 
Standard Definition Television (SDTV)
Standard definition is the most common format broadcast from television stations. By Australian law, all broadcasters must deliver all content in standard definition, with at least 20 hours a week simultaneously broadcasting in high definition format.
The picture quality in SDTV is similar to what you get when you watch a DVD. With SDTV, you get a resolution of 576i, which means 576 horizontal lines interlaced. The more lines there are, the richer the picture quality will be.
Most SDTVs can accept broadcasts in either the standard 4:3 aspect ratio (where it fills out the entire screen) or a 16:9 aspect ratio, which gives you the same panoramic screenshot that you get when you watch the movies.
The sound quality you get on SDTVs is similar to CD quality, or an MPEG digital stereo sound. However, some television programs can be enhanced with Dolby Pro Logic or Dolby Digital surround sound.
Although many Australians still use analogue televisions, they can still get access to SD digital picture quality if their analogue television is connected to a digital set top box.
High Definition Television (HDTV)
High definition provides – as the name suggests – a higher picture quality than standard definition. It can provide up to twice the horizontal and almost three times the vertical resolution of standard definition, going up to as high as 1080i. Such rich picture quality is especially useful when viewing HDTV on larger screens.
Other reasons behind HDTV’s popularity are better sound quality and the release of next-generation high definition console games such as XBOX 360. Such improvements greatly enhance television watching and enable viewers to feel even more immersed in the action – especially since action on television now looks more life-like and natural.
Because HDTV is still new in Australia, not many programs are broadcast in high definition format. To cater to HDTV needs, commercial television stations were required by law from August 2003 to broadcast a minimum of 1,040 hours of high definition content a year.
There are currently almost 50 different shows available in high definition every week across all the free-to-air channels. Some of these programs are in genuine HD formats while others have been converted from the standard definition format. Learn more about HDTV in Australia .
In Canberra, TransACT television broadcasts in standard definition format, except for pure high-definition channels such as ABC2 (a channel showing mostly arts, cultural and local/regional news and information).