Buying guide: TVs
- — 29 September, 2010 10:10
Why are digital TV pictures sharper than analogue TV pictures? Digital TV images are sharper because they are designed to be free from errors. With analogue television signals, even the slightest interference can soften the image. Digital TV doesn't have this problem as things that cause interference with analogue don't have any effect on digital signals. If you live in an area that is within the coverage zones for digital TV, and use an outdoor antenna, you should receive crisp and clear images. The Australian Government's Digital Ready Web site notes that it is important to have a good quality signal for a digital receiver as the picture and sound will suddenly break up if the quality falls below a threshold. Also note that picture break-up can also be caused by interference generated by electrical equipment for example, your hair drier or a fan.
Is audio better on digital TV than on analogue? Yes. Analogue audio is only capable of two channel stereo whereas digital TV can do full Dolby Digital 5.1 surround sound. If you have a home theatre setup, you will definitely notice the difference. However, since the signal is digital, even stereo audio will more than likely sound better as it is not subject to poor reception issues like analogue.
What is widescreen? Widescreen refers to television screens which are much wider than they are high. This width to height measurement is called the aspect ratio. The widescreen ratio is 16 to 9, which can also be written as 16:9. The 16:9 aspect ratio means that for every 16cm wide the screen is, it is 9cm tall. Cathode ray tube (CRT) televisions generally have an aspect ratio of 4:3. On a 4:3 aspect ratio, for every 9cm high the screen is only 12cm wide. As you can see, this means that a widescreen display is much wider than a regular 4:3 television.
What are Standard Definition (SD) pictures? Standard Definition pictures are made up of 576 horizontal lines or less. For example, regular DVDs are Standard Definition at 576i. This resolution uses 576 horizontal interlaced lines to produce an image and is the standard PAL video format. In Australia, there is another 576 line signal format called 576p which is considered to be High Definition. This seems a little confusing but the difference is that the Standard Definition version is interlaced while the HD version is progressive.
A progressive signal shows each frame of the video 30 times per second while an interlaced signal shows half of each frame at a time (called a field) and does so 60 times per second. Even though 60 is a larger number than 30, that doesn't make it better quality because the 60 images are each only half a frame and all those halves have to be stuck back together. This often causes problems, particularly when watching fast moving images. The 576i version is considered Standard Definition because it doesn't look as good as the 576p version and uses less bandwidth to transmit. However, while some consider 576p to be High Definition, it is a point of contention.
What are High Definition (HD) pictures? High Definition TV is transmitted in 576p, 720p or 1080i. These numbers refer to the number of horizontal lines in the image. As you can imagine, the higher the number of lines in the image the crisper and clearer it becomes. Exactly what is considered High Definition can get a little confusing. When it comes to digital TV, television networks consider 576p, 720p and 1080i to be High Definition broadcast signals. However, TV manufacturers dismiss 576p as a HD format and only consider 720p and 1080i to be High Definition. While all modern televisions support 576p, the new wave of High Definition movies and games have a minimum resolution of 720p and anything below that resolution is considered Standard Definition. It all seems contradictory when it comes to 576p but it is really just two different definitions of HD, one from the TV networks and one from the TV manufacturers. Since 576p is still supported on all flat panel TVs, it won't affect you as the consumer.
There is also the 1080p format which is commonly referred to as Full High Definition. TV programs are not broadcast in 1080p, but 1080p movies and programs are available on Blu-ray discs. Games on the Microsoft Xbox 360 and Sony PlayStation 3 are also available in 1080p.
What is Freeview? Freeview is the name used by Australia's free-to-air broadcasters for their digital television services. It is a marketing platform for digital TV that launched in 2009, and it offers an Electronic Program Guide for ABC, SBS, the Seven, Nine and Ten networks, as well as regional broadcasters WIN, Prime Media and Southern Cross. Some products, such as personal video recorders (PVRs), will have a Freeview logo; this means that Freeview has approved their use with Australian digital TV services. However, many products don't have Freeview endorsement but will still work just fine.
What are program enhancements? Program enhancements are an added service not currently available in this country. They are essentially extra channels of video, audio or text information that relate to what is being played in the main channel and can include anything from extra camera angles to statistics and information for sporting events.
What is closed captioning? Closed captioning is a subtitle service for use by the deaf and hearing impaired. It is not available on all programs but when it is, it provides real-time subtitles for what is being said on screen. English language news and current affairs programs between 6.00pm and 10.00pm provide closed captioning across all channels. This is provided using the teletext system on teletext channel 801. Most set-top boxes should provide teletext functionality but you should be sure to check if closed captioning is important to you, since not all are compatible.