competing mobile TV standard. T-DMB (ETSI standard TS 102 427 and TS 102 428) uses MPEG-4 H.264 for video and HE-AAC V2 for the audio, together encapsulated in an MPEG-2 transport stream (TS). The encoded TS is broadcast on DAB in data stream mode. Application devices include mobile phones, portable TV, and PDAs as well as data/ radio for cars. See also: DVB-H, MediaFLO

DMD™ (Texas Instruments Inc.) Digital Micromirror Device. A silicon integrated circuit used to modulate light in a wide variety of applications. The most common use is in electronic projection systems where one or more devices are used to create high quality color images. See also: DLP, DLP Cinema Website: www.dlp.com

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DNxHD Avid’s ‘mastering-quality’ HD codec with intra-frame compression designed for multi-generation compositing with reduced storage and bandwidth requirements. It has four levels to match quality requirements and manageable data volumes. 145 or 220 Mb/s 8-bit and 220 Mb/s 10-bit all at 4:2:2. There is also a 36 Mb/s version for HD offline. This offers HD post at SD data rates, or less, meaning that infrastructure and storage requirements can be as for uncompressed SD. DNxHD is currently undergoing standardization by SMPTE and may be designated VC-3. Website: www.avid.com/dnxhd

Dolby Dolby Digital (DD/AC-3) A digital audio compression system that uses auditory masking for compression. It works with from 1 to 5.1 channels of audio and can carry Dolby Surround coded two-channel material. It applies audio masking over all channels and dynamically allocates bandwidth from a ‘common pool’. Dolby Digital is a constant bit rate system supporting from 64 kb/s to 640 kb/s rates; typically 64 kb/s mono, 192 kb/s two-channel, 320 kb/s 35 mm Cinema 5.1, 384 kb/s Laserdisc/DVD 5.1 and DVD 448 kb/s 5.1. DVD players and ATSC receivers with Dolby Digital capability can provide a backward-compatible mix-down by extracting the five main channels and coding them into analog Dolby Surround for Pro Logic playback.

Dolby Digital Plus Offers more, better quality, channels and supports data rates up to 6 Mb/s. is backwards compatible with Dolby Digital players and is offered as 7.1 channels on HD DVD and Blu-ray with data rates up to 3 and 1.7 Mb/s respectively.

Dolby E An audio compression scheme which can encode/decode up to eight channels plus metadata – typically 5.1 mix (six channels) and Rt/Lt (Right Total/Left Total surround) or stereo two-channel mix, etc – onto two AES/ EBU bitstreams at 1.92 Mb/s (20-bit audio at 48 kHz). Thus video recorders, typically with four channels, can support the greater channel requirements of DVD and some DTV systems (e.g. ATSC). With audio frames matching video frames, Dolby E is a professional distribution coding system for broadcast and post production which maintains quality up to 10 code/recode cycles. Dolby E is widely used in HD production to carry 5.1 sound. As it is locked to video frames it has to be decoded and re-coded to work with a frame-rate conversion process.

Dolby Surround

(a.k.a. Dolby Stereo, Dolby 4:2:4 Matrix) offers analog coding of four audio channels – Left, Center, Right, Surround (LCRS), into two channels referred to as Right Total and Left Total (Rt, Lt). On playback, a Dolby Surround Pro Logic decoder converts the two channels to LCRS and, optionally, a sub-woofer channel. The Pro Logic circuits steer the audio and increase channel separation.

Dolby TrueHD

A lossless compression system designed for high-definition disk-based media, claims to be bit-for-bit identical to the studio master. Running up to 18 Mb/s up to eight 24-bit/96 kHz channels are supported on HD DVD and Blu-ray Disc standards, and is expected to feature in future A/V receivers and downloadable media. It can connect over HDMI. See also: Auditory masking, ATSC, Discrete 5.1 Website: www.dolby.com

Dominance

Field dominance defines whether a field type 1 or type 2 represents the start of a new interlaced TV frame. Usually it is field 1 but there is no fixed rule. Dominance may go unnoticed until flash fields occur at edits made on existing cuts. Replay dominance set the opposite way to the recording can cause a juddery image display. Much equipment allows the selection of field dominance and can handle either.

Down conversion

Down conversion is down-resing and/or changing vertical refresh rates (frame or field rates). For instance, moving from 1080/60I to 576/50I is a down-conversion. See also: Cross conversion, Standards conversion, Up-res, Versioning

Down-res

Decreasing the size of video images to fit another format. Typically this reduces an HD format to an SD format and, as the input images represent over-sampled versions of output, the final quality should be excellent – better than an SD-shot original. Moving from 1080/60I to 480/60I is down-resing. Note that down-res does not include any change of frame rate. See also: Down conversion, Format conversion, Standards conversion, Up-res, Versioning

DPX

SMPTE file format for digital film images (extension .dpx) – ANSI/SMPTE 268M-1994. This uses the same raster formats as Cineon and only differs in its file header. See Cineon file Website: www.cineon.com/ff_draft. php#tv

DRAM

(1) see RAM (2) Informal measure of Scotch Whisky

Drop-frame timecode

Alteration of timecode to match the 1000/1001 speed offset of NTSC transmissions and many newer HD video formats used in ‘NTSC’ countries – including the USA, Canada and Japan. 525-line NTSC at a nominal 30 f/s actually runs at 29.97 f/s and 1080-line HD uses the same frame rate. Even the 24 f/s of film gets modified to 23.97 when applied to TV in ‘NTSC’ countries. With timecode locked to the video, it needs to make up 1 in 1001 frames. It does this by counting two extra frames every

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GLOSSARY OF TERMS