HDTV - High Definition Television

HDTV

High-definition television (HDTV) is a digital television broadcasting system with a significantly higher resolution than traditional formats (NTSC, SECAM, PAL).
While some early analogue HDTV formats were broadcast in Europe and Japan, HDTV is usually broadcast digitally, because digital television (DTV) broadcasting requires much less bandwidth if it uses enough video compression. HDTV technology was first introduced in the United States during the 1990s by a group of electronics companies called the Digital HDTV Grand Alliance.

Screen Resolution

HD Televisions need to be able to display pictures at the resolution set by the new standard. Resolution can be described either in terms of "lines of resolution," or pixels. The resolution you see on your TV depends on two factors, namely the resolution of your display and the resolution of the video signal you receive. Because video images are always rectangular in shape, there is both horizontal resolution and vertical resolution to consider.
A High Definition Digital TV signal delivers significantly more picture detail and audio quality than a standard signal, producing pictures that are significantly better, sharper and clearer.

Horizontal Resolution

This is the number of horizontal lines that can be resolved in an image from top to bottom. The old familiar CRT TV displays 576 lines, while Digital HD television operates at a resolution of either 720 or 1080 lines. This is the most important resolution as it is most noticeable to the human eye.

Vertical Resolution

This is the number of vertical lines that can be resolved from one side of an image to the other. Horizontal resolution varies depending on the source. The number of horizontal pixels is not quite so critical as vertical resolution as it is not as obvious to the human eye during normal viewing.

720p

720p is a screen resolution of 1,280x720 pixels, a High-definition picture that is displayed progressively. Each line is displayed on the screen simultaneously, therefore it is smoother than an interlaced picture.

1080i

1080i, is a screen resolution of 1,920x1,080 pixels. A High-definition picture that is displayed interlaced. Each odd line of the picture is displayed, followed by each even line, and the resulting image is not as smooth as a progressive feed. 1080i is therefore a more detailed picture suited to documentaries and wildlife footage, though less suitable for action-oriented material such as sports and films.

1080p

1080p, is a screen resolution of 1,920x1,080 pixels. High-definition picture that is displayed progressively. Each line is displayed on the screen simultaneously, therefore it is smoother than an interlaced picture. This is the ultimate high-definition standard -- the most detailed picture, displayed progressively.

HD Ready

The HD ready logo is designed to show you that a product is ready to handle High Definition television pictures. This also applies to other equipment like games consoles, satellite receivers, computer screens, disk players and hard drive video recorders.

HDMI

HDMI stands for High Definition Multimedia Interface. This is a bit of a mouthful. Basically it is a standardised format for the cables and sockets that connect the different pieces of an HDTV system together. It is a replacement for the commonplace SCART connection that is currently in use, as SCART is not capable of handling the high quality HD picture format.

Feed Source

The Feed Source is the origin of what you are watching on the television. This could be say, a television programme broadcast by Sky, a film on disk, a game you are playing on a console, or a movie clip you downloaded to a PC.

Sky HD

Sky HD is the brand name of the HDTV service launched by BSkyB on 22 May 2006 in the UK and the Republic of Ireland to enable high definition channels on Sky Digital to be viewed. The service requires the user to have a Sky HD Digibox (costing £299/€449), and an HD ready TV. Customers who pre-ordered by paying a £30/€45 deposit before 6 April 2006 were the first to enjoy the service, with installations starting on 22 May 2006.

Subscription Service (UK Only)

A subscription to the Sky HD service carries an extra £10/€15 per month fee on top of the standard Sky subscription. This fee allows customers to view the equivalent HD channels of their chosen channel package. To receive all HD channels, one must subscribe to the Sky Movies and Sky Sports packages.
Without a subscription to Sky Movies or Sky Sports, Sky Movies HD and Sky Sports HD respectively, will not be available.If you subscribe to any Sky Digital package, the Sky HD subscription also includes a Sky+ subscription and enables the PVR features of the box. (A Sky+ fee was previously charged at an additional £10/€15 per month, or waived if you subscribed to a premium package including sports and/or movies).

This does not apply if you have a FreeSat agreement – Sky will charge £10 for HD and an additional £10 for Sky+ (the Sky+ £10 charge was dropped in early 2007; the Sky HD page What does it cost? has more details).

BBC HD

The BBC is currently running a trial channel called BBC HD, available on the Astra 2D satellite. It is expected that this will evolve into a full channel on satellite and cable, carrying HD content principally from BBC One, when the BBC Trust has concluded its consultation, due by November 21, 2007.

BBC HD was first available to viewers of the Astra 2D satellite (Sky HD EPG No. 143) and Virgin Media cable service subscribers (EPG No. 108) with the suitable reception equipment. The channel was also broadcast as a digital terrestrial (DVB-T) service from London's Crystal Palace Transmitter until May 2007, enabling the channel to be viewed by a selected trial group of 450 homes. Both the satellite and terrestrial broadcasts were free to air, which means that anybody with the required equipment (for example, an adequately powerful personal computer with a DVB-S or DVB-T interface and suitable software) was be able to view the channel during the trial.

The broadcasts are typically at a resolution of 1440x1080, and encoded in H.264/MPEG-4 AVC.
The BBC has, therefore, been the only terrestrial broadcaster so far to offer a "platform neutral" HD offering. ITV's trial HD channel was not available by satellite, but was carried on cable. Channel 4 and Five carried out broadcasts in HD, although these were very limited and only available as part of the closed Freeview trial in London.