HD - High Definition
SDTV and Aalogue broadcasts
What is HDTV?
What is the Benefits of HDTV to me?
What do I need in order to receive HDTV signals?
What if I don’t have HDTV?
Is the Digital Switchover related to High Definition?
Glossary of Terms
Before explaining HDTV, you have probably heard of or read terms such as SDTV or Analogue broadcasts – so what are they exactly?
The traditional household Television (you know - the one that takes up a significant amount of space in the living room) contains an analogue tuner and receives analogue broadcasts only ( BBC1, BBC2, ITV1, Channel 4 and Channel 5)
Many new LCD televisions now contain a digital receiver (look out for the term IDTV in the specifications of the TV) instead of an analogue tuner. This digital tuner allows you access to all Freeview(link to freeview website) terrestrial digital channels and radio stations (currently over 40 television channels - subject to coverage in your area). Freeview is broadcast digitally but is only Standard Definition Television or SDTV.
High Definition Television or HDTV as its more commonly known is the biggest thing to happen in TV broadcasting since the change from black and white to colour!
Resolution, or picture detail, is the main reason why HDTV programs look so good. The standard-definition programming (SDTV) most of us watch today has at most 480 visible lines of detail, whereas HDTV has as many as 1080. HDTV looks sharper and clearer than regular TV by a wide margin, especially on big-screen televisions.
It actually comes in two different resolutions, called 1080i and 720p. One is not necessarily better than the other; 1080i has more lines and pixels, but 720p is a progressive-scan format that should deliver a smoother image that stays sharper during motion. Another format is also becoming more well-known: 1080p, which combines the superior resolution of 1080i with the progressive-scan smoothness of 720p. True 1080p content is extremely scarce however, and none of the major networks have announced 1080p broadcasts. Take a look at our comparison chart to see how HDTV competes up against standard TV and progressive-scan DVD.
| Name | Resolution | HDTV | Wide-screen? | Progressive-scan? | 1080p | 1920 x 1080 | Y | Y | Y |
| 1080i | 1920 x 1080 | Y | Y | N |
| 720p | 1280 x 720 | Y | Y | Y |
| Widescreen 480p (DVD) | 852 x 480 | N | Y | Y |
| Regular TV | Up to 480 lines | N | N | N |
- HD has 2.1 million or more pixels. That is a lot more picture information and that is what makes HDTV so crisp and detailed.
- HD has an aspect ratio of 16:9 versus the 4:3 aspect ratio of analogue. You get one-third more image area and it's that much easier to watch movies in their original format. The 16:9 aspect ratio actually more closely matches the viewing angle of the human eye, making for a more immersive entertainment experience.
- HD images are made up of from 720 to 1080 horizontal scan lines. Again, a lot more detail is possible with that much more visual information on the screen.
- HDTV can provide 5.1 channel Dolby Digital sound, equal to what you hear in a cinema. Plug in a home theatre audio system and you can hear the distinctions between sound effects, dialogue and music. Analogue can't offer anything close to that!
With so much more visual information (more pixels and more scan lines), HDTV provides amazing detail. In fact, many people are startled by the amount of detail they see. And the multi-channel sound and widescreen format make the experience even more rewarding.
What do I need in order to receive HDTV signals?
In order to enjoy the benefits of HDTV you’ll need
You’ll also need a HD receiver. Sky have launched their High Definition service and offer the widest range of HD programmes in the UK. If you have a HD-DVD or Blu Ray player or a HD gaming console such as an XBOX 360 or Playstation 3, they are the perfect companion!
If you have not yet invested in a high definition broadcast service but are considering purchasing a new TV, you will only be future proofing yourself by opting for a HD Ready TV now. You will still be able to receive and display standard analogue and digital broadcasts.
Is the digital switchover related to High Definition?
If you are looking into replacing your current analogue television or upgrading your existing LCD television you are probably aware of the “digital switchover”.
With regards to “is the digital switchover being related to High Definition?” the answer is “No”.The digital switchover is an initiative to switch off all analogue broadcasting and move to digital. This is happening across Europe and some analogue services have already been turned off. The benefits will include extra TV channels as standard, access to subscription services, improved picture and sound quality. Many households already receive digital services via cable or satellite but after the switchover, almost everywhere will be able to receive digital terrestrial television.
If you are still receiving analogue only broadcasts, you will need to ensure you have the correct equipment to receive digital broadcasts. Conventional analogue TV’s will not work after the switchover unless you have a digital set top box attached to them.
A digital product which carries the DVB logo, means that it is designed to work before, during and after the digital switchover. On LCD TV’s the DVB means that it offers an integrated digital tuner (DVB-T) for the viewing of free to air terrestrial digital TV broadcasts without needing a set-top box. Your TV should also allow the reception of pay TV channels through a common interface.
On some LCD televisions you will see in the specifications they have a “common interface slot”. The common interface (CI) is used for accessing pay for viewing channels (such as TopUP TV or Setanta Sports) by plugging in a conditional access module (CAM). These CAM’s are usually available in major retailers and stockists and are usually accompanied by a smartcard which is plugged into the CAM to enable pay for view channels.
Brightness
Comparing published specifications for brightness values is difficult – measurement criteria differs between manufacturers and the race to quote the highest brightness and contrast values has lead to ‘dynamic brightness’ modes which through the use of extra circuitry can allow manufacturers to publish extremely high brightness and contrast values.
It is published that LCD does slightly better than plasma in bright light conditions, but that plasma has the edge in darker environments so also consider whether you will watching TV in a bright and breezy living space or a room with limited or artificial light sources.
Colour
It is generally agreed that LCD offers a sharper image than plasma and that colour is more vibrant. Plasma used to be said to produce a more realistic and wider range of colour, but LCD manufacturers have closed the gap from previous generations of LCD and plasma by incorporating colour spectrum management and tuning technologies to achieve truer, more realistic colour reproduction.
Contrast
Contrast is the measurement of the darkest black compared to the brightest white and plasma does have the ability to display blacks slightly more accurately than LCD. The result is improved contrast in darker scenes. So again, consider your environment and lighting conditions before deciding which technology to chose.
The thing to remember is that brightness and contrast are inexplicably linked. The contrast ratio is how many times brighter the brightest possible output of the screen is and if the circuitry of a product is not first class, pushing up brightness can lead to poor contrast and the ability to display true black – resulting in poor colour reproduction.
Aspect Ratio
The ratio of a pictures width in relation to its height. A traditional TV has a 4:3 aspect ratio and widescreen TV’s have an aspect ratio of 16:9.
Component Video (YpbPr)
Superior to S-video and composite video, three connectors (red, green & blue RCA jacks) that transmit component video signals.
DVB-T Digital Video Broadcasting – Terrestrial.
It will be the digital broadcasting method via terrestrial networks in Europe in the switchover from analogue to digital transmission. To receive new digital TV signals with interactive services, a TV with build-in tuner supporting DVB-T is all that is required.
DVI Digital Visual Interface.
A video interface standard designed to maximise visual quality. Your LCD must have DVI (with HDCP) or HDMI to be considered HD Ready.
HD Compatible
HD Compatible can accept HDMI signals but it does not have the physical resolution requirements of 720 vertical lines that HD Ready products do.
HD Ready
High-definition ready is the official term for products with the ability to receive and display high definition broadcastings.
HDCP
High-bandwidth Digital Content Protection is a copyright protection system that is applied to HDMI and can also be applied to DVI in order to protect video content from being copied.
HDMI
High Definition Multimedia Interface is an uncompressed digital audio/ video interface. It provides a link between any compatible source and receiver. HDMI supports standard, enhanced, or high-definition video, plus multi-channel digital audio on a single cable.
Interlacing
A scanning system where odd/even fields are transmitted so half the image is displayed each time a scan beam moves down the screen. The two fields are displayed so quickly that the human eye only ever sees one image.
PIP
Picture in Picture mode allows the user to display a smaller window within another larger window. Two independent tuners or signal sources are required to supply the large and the small picture.
Progressive Scan
Progressive scan is the method of displaying images where each line of a frame is drawn in sequence instead of alternate rows, as in the interlace method. The result is a sharper image than when the interlace method is used.
SCART
Most commonly used connection for AV equipment such as TV’s, DVD and video players and games consoles. SCART can carry composite, S-Video, RGB video and stereo audio input/ output over in a single connector.
STB
A set-top box connects to a television and converts signals into content that is then displayed as viewable images on the screen.
SDTV
SDTV simply stands for Standard Definition Television and is the 480 interlaced (480i) format for digital, as opposed to the analogue 480i of PAL, SECAM and NTSC.
Widescreen
Widescreen refers to an image or film that has a wider aspect ratio than the traditional TV and computer display format of 4:3 (meaning the screen is a ratio of 4 units wide to three units tall. Also expressed as 1.33:1). In general, an aspect ratio of 1.66:1 is considered widescreen.