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| Freeview HD |
Freeview HD offers high definition TV from the BBC, ITV and Channel 4 without subscription via a TV aerial. You will need a Freeview HD receiver or Freeview HD TV.
Freeview HD was the first operational TV service in the world using the DVB-T2 standard, which will require the purchase of new compatible reception equipment. A fifth channel may be available in the future, Channel 5HD may join in 2012.
The signal is encoded with MPEG-4 AVC High Profile Level 4, which supports up to 1080i30/1080p30, so 1080p50 cannot be used.
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| The system has been designed from the start to allow regional variations in the broadcast schedule. Services will be statistically multiplexed, which means bandwidth is dynamically allocated between channels, depending on the complexity of the images – with the aim of maintaining a consistent quality, rather than a specific bit rate. Video for each channel can range between 3Mb/s and 17Mb/s. Dolby Digital audio will be transmitted at 320Kb/s for 5.1 surround, with stereo audio at 128Kb/s; audio description takes up 64Kb/s, subtitles 200Kb/s and the data stream, for interactive applications, just 50Kb/s. |
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| Technical Information |
The Digital TV Group publishes and maintains the UK technical specification for high-definition services on digital terrestrial television (Freeview) based on the new DVB-T2 standard. The specification is known as the D-book. Freeview HD is the first operational TV service in the world using the DVB-T2 standard. This standard is incompatible with DVB-T, and can only be received using compatible reception equipment.
Some television receivers sold before the HD launch claimed to be "HD-ready", but this usually implies that the screen can display HD, rather than that DVB-T2 signals can be received, a suitable tuner (typically built into a STB or PVR) is additionally required. Freeview HD set-top boxes and televisions are available. In order to qualify for the Freeview HD logo, receivers will need to be IPTV-capable and display Freeview branding, including the logo, on the electronic programme guide screen.
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The Freeview HD trademark requirements state that any manufacturer applying for the Freeview HD logo should submit their product to the Digital TV Group's test centre (DTG Testing) for conformance testing.
On 2 February 2010, Vestel became the first manufacturer to gain Freeview HD certification, for the Vestel T8300 set top box. Humax released the first Freeview HD reception equipment, the Humax HD-FOX T2, on 13 February 2010. |
| It was announced on 10 February 2009 that the signal would be encoded with MPEG-4 AVC High Profile Level 4, which supports up to 1080i30/1080p30, so 1080p50 cannot be used. The system has been designed from the start to allow regional variations in the broadcast schedule. Services are statistically multiplexed – bandwidth is dynamically allocated between channels, depending on the complexity of the images – with the aim of maintaining a consistent quality, rather than a specific bit rate. Video for each channel can range between 3 Mb/s and 17 Mbit/s. AAC or Dolby Digital Plus audio is transmitted at 320 kb/s for 5.1 surround sound, with stereo audio at 128 kbit/s; audio description takes up 64 kbit/s, subtitles 200 kbit/s and the data stream, for interactive applications, just 50 kbit/s. Recording sizes for Freeview HD television transmissions average around 3 GB per hour. Between 22 and 23 March 2011, an encoder software change allowed the Freeview version of BBC HD to automatically detect progressive material and change encoding mode appropriately, meaning the channel can switch to 1080p25. |
| To ensure provision of audio description, broadcasters typically use the AAC codec. Hardware restrictions allow only a single type of audio decoder to operate at any one time, so the main audio and the audio description must use the same encoding family for them to be successfully combined at the receiver. In the case of BBC HD, the main audio is coded as AAC-LC and only the audio description is encoded as HE-AAC. Neither AAC nor Dolby Digital Plus codecs are supported by most home AV equipment, which typically accept Dolby Digital or DTS, leaving owners with stereo, rather than surround sound, output. Transcoding from AAC to Dolby Digital or DTS and multi-channel output via HDMI was not originally necessary for Freeview HD certification. As of June 2010 the DTG D-Book includes the requirement for mandatory transcoding when sending audio via S/PDIF, and for either transcoding or multi-channel PCM audio when sending it via HDMI in order for manufacturers to gain Freeview HD certification from April 2011. Thus equipment sold as Freeview HD before April 2011 may not deliver surround sound to audio equipment (some equipment may, but this is not mandatory); later equipment must be capable of surround sound compatible with most suitable audio equipment. |
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| Copy Protection |
In August 2009 the BBC wrote to Ofcom after third-party content owners asked the BBC to undertake measures to ensure that all Freeview HD boxes would include copy protection systems as required by the Digital TV Group's D-Book, which sets technical standards for digital terrestrial television in the UK. The BBC proposed to ensure compliance with copy-protection standards on the upgraded Freeview HD multiplex by compressing the service information (SI) data, which receivers need to understand the TV services in the data stream. To encourage boxes to adopt copy protection, the BBC made its own look-up tables and decompression algorithm, necessary for decoding the EPG data on high-definition channels, available without charge only to manufacturers who implement the copy-protection technology. This technology would control the way HD films and TV shows are copied onto, for example Blu-ray discs, and shared with others over the internet. No restrictions will be placed on standard-definition services. In a formal written response, Ofcom principal advisor Greg Bensberg said that wording of the licence would probably need to be changed to reflect the fact that this new arrangement is permitted. The BBC had suggested that as an alternative to the SI compression scheme, the Freeview HD multiplex may have to adopt encryption. Bensberg said that it would appear "inappropriate to encrypt public service broadcast content on DTT".
Ofcom agreed to allow the BBC to limit the full availability of its own and other broadcasters' high definition (HD) Freeview services to receivers that control how HD content can be used. Ofcom concluded that the decision to accept the BBC’s request will deliver net benefits to licence-holders by ensuring they have access to the widest possible range of HD television content on DTT. |
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| Channels |
There are currently four channels available, BBC One HD, BBC HD, ITV1 HD and Channel 4HD (and S4C Clirlun in Wales).
There is also likely to be a fifth HD channel available at some point in the future, after early testing discovered that there would almost certainly be space once the roll-out was complete.
Trials of the combined DVB-T2 and MPEG-4 transmission standard have revealed that it is up to 50 per cent more efficient than current DVB-T/MPEG-2 standards, instead of the 30 per cent improvement expected.
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| Screen Resolution |
The three channel (BBC HD, ITV1 HD and Channel 4 HD), 720-line Freeview HD service will be encoded with MPEG-4 AVC High Profile Level 4, which supports up to 1080i30/1080p30, so 1080p50 cannot be used (no Full HD). The HD multiplex will use DVB-T2, not DVB-T.
What does this mean? Well the number, 1080, represents the number of rows of pixels from top to bottom. So a 1080p LCD TV has 1080 rows of pixels. The letter next to 1080 (i.e. 1080i or 1080p) stands for either ‘interlaced’ or ‘polarised’.
In theory, 1080p is better than 1080i. 1080p is referred to as Full HD.
So if a Full HD LCD TV is 1080p, what about TVs that are 720p or 720i? These are known as HD Ready and these usually have a vertical resolution of 720 - however, 1080i TVs are also called HD Ready.
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| A 1080p Full HD TV or a 1080i HD Ready TV will display Freeview HD in its full glory. An 720i or 720p HD Ready TV will also display Freeview HD, but it will have to digitally process the picture to shrink the 1080 horizontal rows to fit its 720 screen |
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| Further Information |
| BBC Internet Blog Information from the BBC. |
| Freeview Official Freeview website. |
| HDTVFAQ Information on HDTV. |
| HDTV UK Information and news about HDTV in the UK. |
| UK Multiplexes Information on the UK's digital terrestrial multiplexes. |
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