all digital channels are capable of transmitting HDI have no way of verifying or disputing that, but the fact is that not all channels broadcast a HD signal.
The Aussie Gummint says:
What are standard definition (SD) pictures?
Standard definition broadcast quality is superior to that obtained from analog television broadcasts, traditionally viewed on 4:3 television sets, and is ghost-free and in widescreen format. The SD picture resolution is 576 lines x 720 active pixels @ 50Hz interlaced (576i).
The Government requires broadcasters to provide a digital SD signal at all times, even when high definition programs are broadcast. This is to ensure that viewers with SD receivers will always receive a digital television service, even when the higher quality high definition television signal is transmitted.
What are high definition (HD) pictures?
High definition broadcasts have image resolution that is superior to SD and the existing analog television broadcast.
Australian broadcasters are currently using four different levels of HD:
• 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 HD pictures at the highest resolution are particularly noticeable on larger screen sets and when using projection equipment. HD pictures are also ghost-free and in widescreen format. When viewed on a HD capable television screen the viewer can enjoy cinema-quality viewing with Dolby Digital sound (where available with some HD programming).
More information is available from http://www.digitalready.gov.au.