Australian TV stations started broadcasting a digital television signal on January 1st 2001, in addition to the existing analog system.

It began with a whimper rather than a bang, with no equipment available for sale and almost no high definition programming (HDTV) planned at that time.

Things have improved somewhat since then, with most stores now carrying almost exclusively widescreen (16x9) Plasma or LCD TV's. Although a few of these sets still require a set-top box to receive digital signals, most now have inbuilt digital receivers - although not all are capable of receiving full 1080 HD.

All the networks now simulcast in both digital and analogue. The commercial networks, however, have up till now been frustrated by regulations (designed to protect the pay-tv industry) which prohibited them from multi-channel broadcasting. This is now changing, with most networks beginning to transmit different programming on their HD channels at certain times. Interestingly, this programming is not always in HD, and in some cases is even 4x3!

It appears that much of the content on the "HD" channels is actually SD that has been "upscaled", ie, processed up to HD resolution. Although this does usually look better than normal SD, it is not really HD. It is hard to determine which programmes are full HD, since all content on the HD channels is flagged as HD, even if it is just upscaled. One of the first local dramas to go HD was Channel Nine's McLeod's Daughters, which was transmitted in HD for several years. Because it was originated on 16mm film the picture quality in HD was still fairly ordinary, although it did make the film grain much clearer. It also went out with 5.1 sound - something which is still fairly rare for a domestic free-to-air programme, although it is more common in movies, particularly on pay-tv.

Both the ABC and SBS have a second, digital-only channel, as well as HD channels.

The Australian television industry has adopted both Dolby Digital (AC-3) and MPEG audio as the preferred sound formats for Digital TV. Both use data compression to carry anything from mono up to 5.1 audio. Programmes using MPEG appear louder than those in AC3, because of the 4dB attenuation usually built in to AC3. Mildly annoying when channel surfing!

For those of us in the sound fraternity, digital television, even without 5.1, offers interesting possibilities - for one thing, the networks' ubiquitous transmission compression (you know, the boxes that squash our mixes beyond recognition in order to reduce the dynamic range to virtually nothing) is theoretically no longer required (was it ever?). Unfortunately it appears most networks still compress the audio on transmission in both digital and analogue, although probably not so much in 5.1.

There is, by the way, no reason for stations to compress audio on digital TV - they have always done this in analogue for technical/legal reasons, to avoid having the narrow sound notch impinge on the picture signal, causing unsightly "sound bars" on the picture. Stations could lose their licence for allowing this to happen. This is simply not an issue in digital - the normal weighted dialogue level for AC-3 is -27dB, giving plenty of headroom for most programmes.

The preferred delivery format for 5.1 for television has so far been Dolby E (usually on Digital Betacam), but with new video tape formats having up to eight sound tracks, this may not always be the case.

The analogue network is due to be turned off by the end of 2013.

© Philip Purcell 2008

How low can you go? The Kross set-top box - $79

A quick look around the shops shows that most retailers now carry a large range of digital TV's (both standard and high-def) and a variety of set-top boxes (STB's). The LCD vs Plasma battle still rages, with CRT sets becoming increasingly rare. There are now very few 4x3 sets being sold. Many of the plasma and LCD monitors are capable of displaying high-definition, and most have a digital receiver built in, although not always HD. Some set-top boxes have a hard drive (these are sometimes called PVR's - personal video recorders) allowing programs to be stored digitally for viewing later, or time-shifted (delayed viewing while still recording). One of the latest of these is the TiVo, regarded as being very user-friendly, if a little expensive. TiVo only works on free-to-air channels while Foxtel's IQ and IQ2 offer similar features for pay tv. Set-top boxes have plummeted in price, with supermarkets carrying some basic models for as little as $79! Even so, many consumers can still view only in analogue, so it is likely the old analogue channels will still be with us for a while yet.

LINKS: Digital TV in Australia Department of Broadband, Communications and the Digital Economy Australian Communications and Media Authority Free TV Australia