Digital-S Assigned as D9, this is a half-inch digital tape format which uses a high-density metal particle tape running at 57.8mm/s to record a video data rate of 50 Mb/s. The tape can be shuttled and searched up to x32 speed. Video, sampled at 8 bits, 4:2:2, is compressed at 3.3:1 using DCT-based intra-frame compression. Two audio channels are recorded at 16-bit, 48 kHz sampling; each is individually editable. The format also includes two cue tracks and four further audio channels in a cassette housing with the same dimensions as VHS.

Digitizer A system which converts an analog input to a digital representation. Examples include analog to digital converters (ADCs) for television signals, touch tablets and mice. Some of these, mouse and touch tablet for example, are systems which take a spatial measurement and present it to a computer in a digital format. See also: A/D, Into digits (Tutorial 1), GUI

Digitizing time Time taken to record existing footage into a disk-based editing system. The name suggests the material is being played from an analog source, which it rarely is now. A better term is ‘loading’. Use of high-speed networking may enable background loading – eliminating digitizing time at an edit suite.

Dirac Dirac is an open and royalty-free video compression format, specification and system developed by BBC Research. Dirac format aims to provide high-quality video compression from web video up to ultra HD and beyond, and as such competes with existing formats such as H.264 and VC-1. The specification was finalised on 21 January 2008, and further developments will only be bug fixes and constraints. In September of that year version 1.0.0 of the reference implementation was released which corresponds to an intra-frame only subset known as Dirac Pro, which has been proposed to the SMPTE for standardisation as VC-2.

Discrete 5.1 Audio Often referred to as ‘5.1’, this reproduces six separate (discrete) channels – Left, Center, Right, Left Rear, Right Rear, and sub-woofer (the .1). All the five main channels have full frequency response which, together with a separate low-frequency sub-woofer, create a three-dimensional effect. Discrete 7.1 Audio is similar but includes more speakers. Discrete 5.1 audio is made available with many HD television broadcasts and is specified on HD DVD and BD media. See also: Dolby Digital

Disk drives See Hard disk drive, Optical disks

Display resolutions The computer industry has developed a series of display resolutions (see below) which span television’s SD and HD, and QXGA is identical to the 2K image size used for digital film production. The availability of hardware to support these resolutions has, and will continue to benefit television and digital film. There is already a QXGA projector on offer. All use square pixels and none correspond exactly to television formats so attention to size and aspect ratio is needed when using computer images on TV and vice versa.

Dither

In digital television, analog original pictures are converted to digits: a continuous range of luminance and chrominance values is translated into a finite range of numbers. While some analog values will correspond exactly to numbers, others will, inevitably, fall in between. Given that there will always be some degree of noise in the original analog signal the numbers may dither by one Least Significant Bit (LSB) between the two nearest values. This has the advantage of providing a means by which the digital system can describe analog values between LSBs to give a very accurate digital rendition of the analog world. With the use of Dynamic Rounding dither can be intelligently added to pictures to give more accurate, better looking results.

DivX

A video codec created by DivX, Inc. which can compress long video segments into relatively small data spaces while maintaining reasonable picture quality. It uses MPEG-4 H.264 or AVC compression to balance quality against file size and is commonly associated with transferring DVD audio and video to hard disks. ‘DivX Certified’ DVD players can play DivX encoded movies.

DLNA

Digital Living Network Alliance aims to deliver an interoperability framework of design guidelines based on open industry standards to complete cross-industry digital convergence. The resulting ‘digital home’ should then be a network of consumer electronic, mobile and PC devices that transparently co-operate to deliver simple, seamless interoperability that enhances and enriches users’ experience. See also: HANA Website: www.dlna.org

DLP™ (Texas Instruments Inc.) Digital Light Processing is the projection and display technology which uses digital micromirror devices (DMD) as the light modulator. It is a collection of electronic and optical subsystems which enable picture information to be decoded and projected as high-resolution digital color images. DLP technology enables the making of very compact, high brightness projectors. See also: DLP Cinema, DMD Website: www. dlp.com

DLP Cinema™ (Texas Instruments Inc.) DLP Cinema is a version of DLP technology that has been developed for digital electronic movie presentation. It contains extended color management and control and enhanced contrast performance. DLP Cinema is a major supplier of the digital cinema market with thousands of DLP Cinema technology-based projectors installed in commercial cinemas around the world. As the technology allows for fast frame rates of more than double the 24 f/s of normal cinema, it can be used to project stereo movies where left and right eye frames are sequenced through one projector – helping to make ‘3D’ movies look good and easy to show. See also: DLP, DMD Website: www.dlp.com

DMB

Digital Multimedia Broadcasting. Developed and first adopted in South Korea (2005), DMB is a digital transmission system for television, radio and datacasting to mobile devices/ phone and can operate over satellite (S-DMB) or terrestrially (T-DMB). DMB is based on the Eureka 147 Digital Audio Broadcasting (DAB) standard, and has similarities with DVB-H, a

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GLOSSARY OF TERMS