High def TV or HD TV has a much sharper better quality picture and sound than Standard TVs to date. You can have near to Cinema quality movies and drama in your own home. To watch HighDef, in addition to your HD Ready set, you will need to have access to a HD TV service which can come via Satellite, Cable or Broadband.
The widest choice of HD channels currently in the UK is with Sky TV who give access to up to 37 channels.
The BBC started trials of HD in May 2006. Now, a growing number of high-definition TV channels are coming on-stream, notably from Sky Digital, the service that is leading the way in UK HD, offering over 30 HD channels.
High Definition is on offer from Sky, Freesat, Virgin Media and a limited service from Freeview HD service.
BT Vision is a digital TV service offered to BT Total Broadband customers throughout the UK.
The BT Vision set-top boxes support High Definition. There’s no live HD content on BT Vision, but you can download HD movies and TV shows over Broadband onto your BT Vision+ box, to watch on your TV in HD.
The two main high-definition formats that you will commonly encounter and that will be used for HDTV for the foreseeable future are 720p and 1080i. There is also a third format 1080p that will be available from next generation games consoles and DVD systems. The formats are specified as follows:
- 720p – 1280×720 pixels @ 50/60Hz Progressive
- 1080i – 1920×1080 pixels @ 50/60Hz Interlaced
- 1080p – 1920×1080 pixels @ 24/25/50/60Hz Progressive
The differences between the three formats above are their resolutions, measured in pixels and their scanning mode; progressive or interlaced. Interlaced and progressive scan are two different ways capturing, transporting and displaying video content.
The two main HDTV broadcast formats; 720p and 1080i exist to cater for needs of different programme material.
Interlacing can cause visible flickering or jagged images when displaying motion, resulting in a reduction in perceived vertical resolution as well as image quality. For fast moving content such as sport, a progressively scanned image is better, so it is likely most sports content will be broadcast in 720p, which provides 50/60 frames a second (Hz) of 1280×720 pixel resolution.
Less fast-moving content can be safely interlaced, and the bandwidth saving this produces can be used to deliver a higher resolution 1080 line image in the case of 1080i, making it suitable for other types of programming. The 1080i format delivers 50/60 higher resolution (1920×1080px) fields which combine to produce half the frame rate at 25 or 30 frames per second.
1080p is unlikely to be used to broadcast HDTV in the near future due to its increased bandwidth requirement. 1080p content will be available from other sources however, including the next-generation DVD formats; HD-DVD and Blu-ray, and also from next-generation games consoles such as the Xbox and Playstation 3. The quality improvement 1080p will provide over the other high-definition formats will be much smaller than the upgrade from standard to high-definition.
