Media
Take-up of high definition services is accelerating in the USA and in other countries, including Australia. With Sky's recent announcement that it is examining technical details for a launch of HD services in its lineup by 2006, it now appears that HDTV will become a reality in the UK over the next few years.
Standard Definition
Standard definition broadcasts are currently available in the UK both on analogue television and the digital platforms. The UK's current TV standard is 576i50 - "576" meaning a 625 line picture, with 576 lines actually displayed, and "i50" meaning an interlaced picture refreshed fifty times per second. "Interlaced" refers to the picture being drawn in two halves - half the picture is drawn with every refresh, resulting in a complete frame being drawn 25 times per second. The practice came about because early TV tubes were incapable of drawing the whole picture before the top of it began to fade, resulting in a picture with uneven brightness and intensity.
High Definition
Digital television utilises compression technology to fit multiple channels onto a single frequency. A digital terrestrial television multiplex, for example, goes out on the air on a single channel, but can carry multiple TV channels. This same compression technology can allow much more picture information to go out on a single channel instead, should the broadcaster desire.
To illustrate the point, consider the digital television situation in the United States. There, local broadcasters each operate their own multiplex. WRAL-TV in Raleigh, North Carolina - the first HD channel in the USA - transmits the following services over the air on channel 5:
5.1: WRAL High Definition - a high definition feed of its local and CBS programming.
5.2: WRAL News Channel - a standard definition channel showing non-stop local news.
5.3: WRAL Standard Definition - a standard definition channel in digital format.
In technical terms, WRAL had the choice of transmitting many standard definition channels or one HD channel and only a couple of standard channels. That's because a high definition channel takes up more space (bandwidth) in a multiplex than a standard definition service because of the vastly increased amounts of data it requires. The good news is that this increased amount of data leads to a clearer, more detailed picture.
As discussed earlier, standard definition broadcasts are 576i50. The European Broadcasting Union's preferred HDTV format is 720p50. As you'll see, the notation remains the same. So, 720p50 means: 720 lines progressively scanned, refreshed fifty times per second. Interlacing is done away with completely - instead, the entire picture is built fifty times per second. The increased resolution results in a much sharper and more detailed picture - hence, "high definition."
So, let's go back to our WRAL example and apply it to the UK. At the time this article was written, DTT multiplex 1 carries BBC1, BBC2, BBC3, BBC News 24, CBBC, CBeebies, BBCi, and various BBC radio services. The BBC made a different choice to WRAL-TV: instead of transmitting a high definition channel and a couple of standard definition services, it chose to fill the multiplex with a lot of SD and radio services.
Both WRAL and the BBC made the right decisions based on the different ways digital and HDTV services have developed in the US and the UK. It will be interesting to see whether or not HD takeup is sufficient after Sky launches HD services in 2006 to warrant a re-examination of the services available on DTT multiplexes.
Where are we now?
The BBC is already producing some content in high definition - a recent example was "The Grid" mini-series, which was a co-production between TNT in the US and the BBC in the UK. It was filmed in a high definition format, and aired in high definition in the USA. Content is ready and available, both from the BBC and other broadcasters around the world. At present though, the only relatively well-known HD service in Europe is Euro1080/HD1. This subscription-based service transmits using the 1080i standard (1080 lines, interlaced picture), and we don't know yet whether it will be switching to the EBU-preferred format. Sky has announced plans to launch a high definition service during 2006, but nothing's been mentioned about possible HD developments on DTT, let alone cable.
HD in the UK is in its infancy - Digital Spy will be following developments closely and updating this guide and our news pages as soon as information becomes available.
Questions and comments are welcome - click the "contact us" link at the top of the page.
Standard Definition
Standard definition broadcasts are currently available in the UK both on analogue television and the digital platforms. The UK's current TV standard is 576i50 - "576" meaning a 625 line picture, with 576 lines actually displayed, and "i50" meaning an interlaced picture refreshed fifty times per second. "Interlaced" refers to the picture being drawn in two halves - half the picture is drawn with every refresh, resulting in a complete frame being drawn 25 times per second. The practice came about because early TV tubes were incapable of drawing the whole picture before the top of it began to fade, resulting in a picture with uneven brightness and intensity.
High Definition
Digital television utilises compression technology to fit multiple channels onto a single frequency. A digital terrestrial television multiplex, for example, goes out on the air on a single channel, but can carry multiple TV channels. This same compression technology can allow much more picture information to go out on a single channel instead, should the broadcaster desire.
To illustrate the point, consider the digital television situation in the United States. There, local broadcasters each operate their own multiplex. WRAL-TV in Raleigh, North Carolina - the first HD channel in the USA - transmits the following services over the air on channel 5:
5.1: WRAL High Definition - a high definition feed of its local and CBS programming.
5.2: WRAL News Channel - a standard definition channel showing non-stop local news.
5.3: WRAL Standard Definition - a standard definition channel in digital format.
In technical terms, WRAL had the choice of transmitting many standard definition channels or one HD channel and only a couple of standard channels. That's because a high definition channel takes up more space (bandwidth) in a multiplex than a standard definition service because of the vastly increased amounts of data it requires. The good news is that this increased amount of data leads to a clearer, more detailed picture.
As discussed earlier, standard definition broadcasts are 576i50. The European Broadcasting Union's preferred HDTV format is 720p50. As you'll see, the notation remains the same. So, 720p50 means: 720 lines progressively scanned, refreshed fifty times per second. Interlacing is done away with completely - instead, the entire picture is built fifty times per second. The increased resolution results in a much sharper and more detailed picture - hence, "high definition."
So, let's go back to our WRAL example and apply it to the UK. At the time this article was written, DTT multiplex 1 carries BBC1, BBC2, BBC3, BBC News 24, CBBC, CBeebies, BBCi, and various BBC radio services. The BBC made a different choice to WRAL-TV: instead of transmitting a high definition channel and a couple of standard definition services, it chose to fill the multiplex with a lot of SD and radio services.
Both WRAL and the BBC made the right decisions based on the different ways digital and HDTV services have developed in the US and the UK. It will be interesting to see whether or not HD takeup is sufficient after Sky launches HD services in 2006 to warrant a re-examination of the services available on DTT multiplexes.
Where are we now?
The BBC is already producing some content in high definition - a recent example was "The Grid" mini-series, which was a co-production between TNT in the US and the BBC in the UK. It was filmed in a high definition format, and aired in high definition in the USA. Content is ready and available, both from the BBC and other broadcasters around the world. At present though, the only relatively well-known HD service in Europe is Euro1080/HD1. This subscription-based service transmits using the 1080i standard (1080 lines, interlaced picture), and we don't know yet whether it will be switching to the EBU-preferred format. Sky has announced plans to launch a high definition service during 2006, but nothing's been mentioned about possible HD developments on DTT, let alone cable.
HD in the UK is in its infancy - Digital Spy will be following developments closely and updating this guide and our news pages as soon as information becomes available.
Questions and comments are welcome - click the "contact us" link at the top of the page.
