Arcing

Aspect ratio conversion.

Bandwidth

The amount of data transmitted in a given time.

Bit rate

A bit is a binary digit representing two different states, either ON or OFF. The bit rate is the number of bits transmitted per second.

Byte

8 bits or 256 discrete items of information such as colour, brightness etc. One full frame of CCIR 601 requires just under 1Mb of storage. One full frame of HD/24p video requires about nine times the storage.

Compression

Compression expresses the given picture will less data and compression rate alone does not give an indication of final picture quality. It is necessary to compress the data in order to store and transmit digital television data using an economical amount of bandwidth. Different rates of compression are used with different and practically, the more data used the better the image quality. Multiple generations of compressed images always result in image degradation.

Common Image Format (CIF)

The internationally accepted 1920x1080 pixels.

Contrast ratio

Refers to the difference in light intensity between the whitest white and blackest black the monitor is able to produce. The higher the ratio, the better the color representation of the monitor. eg a 500:1 contrast ratio is significantly better than a 150:1 contrast ratio. A higher contrast ratio means the monitor is better able to differentiate fine details in color.

Digital cinema

The theatrical display of images originally created electronically, but may be projected on film.

Digital cinematography

Digital acquisition using film-style operational practises.

Dolby E

The preferred digital audio system for HDTV transmission, incorporating eight channels (six channels 5.1 and 2 channels stereo).

Dolby 5.1

Dolby digital full surround sound, front left and right, rear left and right and centre together with a sub-woofer for extra bass.

Downconversion

The reproduction of an image in high definition to a standard definition image.

Frame rate

The number of complete images per second.

Freesat

A digital satellite TV service from the BBC and ITV - with over 80 TV and radio channels. A subscription-free service, only a set-top box and satellite dish are required. Once installed you can receive free HD TV with no additional costs. An alternative to Freeview, Cable and SKY.

HDCAM

The name given by Sony to the family of HD/24p products for acquisition and post.

High-definition television

A video format superior to a PAL or NTSC image, using 16:9. these include 18 different permutations of frame rate and raster lines. Mastering on 24p allows conversion to any of these standards.

Interlace

Video scanning where each frame comprises of two fields which together produce a complete image. Note that the two fields are spaced 1/50 or 1/60 second apart. Two interlace fields are not equivalent to one progressive frame.

JPEG

A compression scheme optimised for still pictures which can reduce image size to up to a hundredth of the original.

LCD

LCD HDTVs work by shining a light behind an LCD panel made up of a fixed number of pixels. Each pixel is either red, blue or green and is switched on or off when a voltage is applied to it. When voltage is applied to a pixel, it is switched off, meaning that light can’t shine through it.
The main advantage of LCD vs plasma HDTV is that LCD panels don’t suffer from what's called burn-in. This is a feature of plasma TVs where they are used to watch TV stations with logos permanently displayed on-screen or where they are used for video gaming with games that have static images such as a cockpit on flight simulators. The image literally ‘burns-in’ the screen meaning that even when the image is not present you can still see a faint trace of it on screen. So for video gamers in particular, LCD is a better choice than plasma.

MPEG

A compression scheme optimised for moving pictures whereby the potential for compression is based on the similarity of successive pictures.

NTSC

A 525-line 59.94Hz composite analogue colour television system at 4.2Mhz bandwidth used in the USA and Japan.

PAL

A 625-line 50Hz composite analogue colour television system at 5.5Mhz bandwidth used in Europe, Australia and other parts of the world.

Pixel

One picture element or one sample of digital picture information.

Plasma

Plasma HDTVs have over a million chambers which house one or a combination of gasses. When a voltage is applied to one of these chambers the gas ionizes and emits ultra-violet light. This light strikes red, green or plue phophors coated on the inside of the chamber and a pixel emits this color light.
Plasma HDTVs tend to have better contrast than LCDs because, even when a pixel on an LCD panel is switched off it doesn’t block all the light coming through and therefore the pixel isn’t completely black. Plasma HDTVs also tend to have a wider viewing angle than LCDs, as on LCD HDTVs the contrast and colour of the image can change when the screen is viewed from different angles.

Progressive

Video capture or display by scanning such that a frame contains a complete image. Each frame contains a complete picture and uses more bandwidth than interlace scanning. Your home computer scans progressively which is why DVD movies look better on a computer than on a conventional television, which is interlace.

Resolution

The technical equivalent of sharpness and the maximum amount of picture information that can be resolved in a reproduced image. Resolution is dependant on the number of pixels and the production tools used such as lenses, film processing, scanning and telecine transfer.

RGB

The signals of red, green and blue.

Segmented Frame

A technique to display a progressive image on a standard interlace monitor.

Spatial Resolution

The resolution/clarity of an image across a static frame.

Temporal Resolution

The resolution/clarity of an image between successive frames.

Upconversion

The reproduction of a lower resolution image such as PAL/NTSC to a higher definition image.

Up-resing

The process whereby an image of a lesser resolution is displayed at a higher resolution to match the quality of the intercut high-resolution material.