minute while the video remains continuous. So 10:35:59:29 advances to 10:36:00:02. In addition, at every ten-minute point the jump is not done. This brings the timecode time almost exactly into step with the video. Timecode that does not use drop-frame is then called non drop-frame time- code. See also: 1000/1001 Website: www.dropframetimecode.org

DSL

Digital Subscriber Line. A general term for a number of techniques for delivering data over the telephone local loop (between exchange and user) – the copper wires that make up the so called ‘last mile’. Referred to generically as xDSL these offer much greater data speeds than modems on analog lines. See also: ADSL

DSLAM Digital Subscriber Line Access Multiplexer – usually located at the local telephone exchange, it connects multiple customer DSL lines to a high-speed ATM internet backbone line. It is the device that communicates with our ADSL (and SDSL) modems, creating a network similar to a LAN but without Ethernet distance restrictions, to provide an Internet connection for subscribers.

DSS

Digital Satellite Service. One of the terms used to describe DTV services distributed via satellite.

DTF and DTF-2 Digital Tape Format for storing data on half-inch cassettes at high data density on the tape and offering fast read and write speeds. Generally it is used for long-term file-based storage and the modern DTF-2 can store 518 GB (uncompressed) per cassette with a sustained data rate of 40 MB/s. In television/digital film applications DTF is often used as the archive in a facility with networked workstations. See also: LTO, SAIT-2

DSM See DCI

DTT

Digital Terrestrial Television – used in Europe to describe the broadcast of digital television services from traditional masts using terrestrial frequencies. See also: ATSC, DVB, ISDB, T-DMB, DMB-T/H For general information on worldwide digital transmission standards see Website: www.dvb.org/ about_dvb/dvb_worldwide

Dual link The bandwidth of SDI and HD-SDI links allow the transport of uncompressed 4:2:2 sampled video and embedded digital audio. Dual links are often used to carry larger requirements – such as video with key (4:2:2:4), RGB (4:4:4) and RGB with key (4:4:4:4). Dual link for SD is defined in ITU-R/ BT.799-2 and RP 175-1997. Dual link at HD is used for stereo3D and 50/60 P. A dual link is arranged to allow some meaningful monitoring of each of the two links with standard equipment. So RGB is sent with Link A carrying full bandwidth G, half R and B (4:2:2). Link B is just half bandwidth R and B (0:2:2). RGB + Key is sent as (4:2:2) and (4:2:2). See also: 0:2:2, 4:2:2, HD-SDI, HSDL, SDI, Y Cr Cb Website: www.itu.ch

Duplex

(Full duplex) refers to communications that are simultaneously two-way (send and receive) – like the telephone. Those referred to as half-duplex switch between send and receive.

DV

This digital VCR format was formed jointly as a co-operation between Hitachi, JVC, Sony, Matsushita, Mitsubishi, Philips, Sanyo, Sharp, Thomson and Toshiba. It uses 6.35 mm (quarter-inch) wide tape in a range of products to record 525/60 or 625/50 video for the consumer (DV) and professional markets (Panasonic’s DVCPRO and Sony’s DVCAM). All recorders use digital intra-field DCT-based ‘DV’ compression (about 5:1) to record 8-bit component digital video based on 13.5 MHz luminance sampling. The consumer versions and DVCAM sample video at 4:1:1 (525/60) or 4:2:0 (625/50) video and provide two 16-bit/48 or 44.1 kHz, or four 12-bit/32 kHz audio channels onto a 4-hour 30-minute standard cassette (125 x 78 x 14.6 mm) or smaller 1-hour ‘mini’ cassette (66 x 48 x 12.2 mm). The data rate is 25 Mb/s. The professional DVCPRO models make use of DV’s hierarchical design, being x2 and x4 versions of the basic 25 Mb/s version.

DVCAM is Sony’s professional variant of DV which records 15-micron tracks on a metal evaporated (ME) tape. As stated, video sampling is 4:2:0 for 625/50 (PAL) and 4:1:1 for 525/60 (NTSC). Audio is four 12-bit, 32 kHz channels, or two 16-bit 48 kHz channels.

DVCPRO is Panasonic’s development of native DV which records 18-micron tracks onto metal particle tape. It uses native DV compression at 5:1 from a 4:1:1, 8-bit sampled source. There are 12 tracks per frame for 625/50 and 10 tracks per frame for 525/60, tape speed is 33.8 mm/s and the data rate 25 Mb/s. It includes two 16-bit digital audio channels sampled at 48 kHz and an analog cue track. Both linear (LTC) and Vertical Interval Timecode (VITC) are supported.

DVCPRO 50

is a x2 variant of DVCPRO. With a tape speed of 67.7 mm/s, a data rate of 50 Mb/s and using 3.3:1 video compression, it is aimed at the studio/higher quality end of the market. Sampling is 4:2:2 to give enhanced chroma resolution, useful in post production processes (e.g. chroma keying). Four 16-bit audio tracks are provided.

DVCPRO HD

also known as DVCPRO100 is a high definition format that can be thought of as four DV codecs that work in parallel. Video data rate depends on frame rate and can be as low as 40 Mbit/s for 24 frame/s mode and as high as 100 Mbit/s for 50/60 frames/s modes. Like DVCPRO50, DVCPRO HD employs 4:2:2 color sampling.

DVCPRO P2 See also: P2 Website: http://panasonic-broadcast.com

DVB

Digital Video Broadcasting, the group, with over 200 members in 25 countries, which developed the preferred scheme for digital broadcasting in Europe. The DVB Group has put together a wide portfolio of broadcast standards; the major ones include a satellite system, DVB-S, and now the more efficient DVB-S2, a matching cable system, DVB-C (and now DVB-C2), and a digital terrestrial system, DVB-T. DVB-H is a newer broadcast standard designed for terrestrial operation with handheld devices where power must be conserved. A mobile-by-satellite standard,

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GLOSSARY OF TERMS