D1 A format for digital video tape recording working to the ITU-R BT.601, 4:2:2 standard using 8-bit sampling. The tape is 19 mm wide and allows up to 94 minutes to be recorded on a cassette. Despite the advantages, D1 use was limited by high cost and is rarely found today. However the term 'D1' is still occasionally used to imply uncompressed component digital recording - 'D1' quality. See also: D2, DVTR
D2 A VTR standard for digital composite (coded) PAL or NTSC signals. It uses 19 mm tape and records up to 208 minutes on a single cassette. Neither cassettes nor recording formats are compatible with D1. Being relatively costly and not offering the advantages of component operation the format has fallen from favor. VTRs have not been manufactured for many years. See also: Component, D1, D3, DVTR
D3 A VTR standard using half-inch tape cassettes for recording digitized composite (coded) PAL or NTSC signals sampled at 8 bits. Cassettes record 50 to 245 minutes. Since this uses a composite PAL or NTSC signal, the characteristics are generally as for D2 except that the half-inch cassette size allowed a full family of VTR equipment to be realized in one format, including a camcorder. D3 is rarely used today.
D4 There is no D4. Most DVTR formats hail from Japan where 4 is regarded as an unlucky number.
D5 A VTR format using the same cassette as D3 but recording uncompressed component signals sampled to ITU-R BT.601 recommendations at 10-bit resolution. With internal decoding, D5 VTRs can play back D3 tapes and provide component outputs. D5 offers all the performance benefits of D1, making it suitable for high-end post production as well as more general studio use. Besides servicing the current 625 and 525 line TV standards the format extends to HDTV recording by use of about 4:1 compression (HD-D5).
D6 A little used digital tape format which uses a 19mm helical-scan cassette tape to record non-compressed HDTV material. The Thomson VooDoo Media Recorder is the only VTR based on D6 technology. The format has passed into history.
D7 This is assigned to DVCPRO.
D9 This is assigned to Digital-S.
D10 This refers to Sony's MPEG IMX VTRs that record I-frame only 4:2:2-sampled MPEG-2 SD video at 50 Mb/s onto half-inch tape. In bit rate, this sits IMX between Betacam SX and Digital Betacam. There is a Gigabit Ethernet card available which has caused some to dub it the eVTR as it can be considered more as a 'storage medium' for digital operations.
D11 The HDCAM VTR format has been assigned D11.
D12 This is assigned to DVCPRO HD.
D-20 A film-style digital camera from Arri that is highly modular and uses a single Super35mm-sized image CMOS sensor with a Bayer filter and producing the same field of view and depth of field as that of traditional 35mm film motion picture cameras. Like real film cameras it uses a detachable optical viewfinder - that is widely preferred to electronic versions on other cameras. It is capable of 1-60Hz frame rates, produces 1080-line images in 4:2:2 or 4:4:4. Website: www.arri.com
DAS Direct Attached Storage, typically on hard disks, is available only to a single user as opposed to NAS that can be available to everyone on the network. Typically this uses SCSI, SAS or Fibre Channel protocol and provides add-on storage for servers that maintains high data rate and fast access.
Data carousel This is a file system that rotates and delivers its content into a network at a defined point in a cycle - for example, teletext pages. It is a method to make a large amount of information or data files available within a reasonably short time after a request. The data is inserted into the digital broadcast transport stream. See also: IP over DVB
Data scanner Sometimes used as a generic term for film scanner.
Data recorders Machines designed to record and replay data. They usually include a high degree of error correction to ensure that the output data is absolutely correct and, due to their recording format, the data is not easily editable. These compare with digital video recorders which will conceal missing or incorrect data by repeating adjacent areas of picture and which are designed to allow direct access to every frame for editing. Where data recorders are used for recording video there has to be an attendant 'workstation' to produce signals for video and audio monitoring, whereas VTRs produce the signals directly. Although many data recorders are based on VTRs' original designs, and vice versa, VTRs are more efficient for pictures and sound while data recorders are most appropriate for data. They are useful for archiving and, as they are format-independent, can be used in multi-format environments. See also: DTF, LTO
Datacasting Broadcasting data. See: IP over DVB
dB See Decibel
DC28 SMPTE Task Force On Digital Cinema - intended to aid digital cinema development by determining standards for picture formats, audio standards and compression, etc.
DCI Digital Cinema Initiatives, LLC was formed in 2002 with members including Disney, Fox, MGM, Paramount, Sony Pictures Entertainment, Universal and Warner Bros. Studios. Its purpose was to establish and document specifications for an open architecture for Digital Cinema components that ensures a uniform and high level of technical performance, reliability and quality control. It published the Digital Cinema System Specification in July 2005 (freely available at their website) establishing a set of technical specifications that have allowed the industry to move forward and start a large-scale roll-out of Digital Cinema. DCI describes a workflow from the output of the feature post production or DI, termed the Digital Source Master (DSM), to the screen. The Digital Cinema Distribution Master (DCDM) is derived from the DSM by a digital cinema post production process, and played directly into a digital cinema projector and audio system for evaluation and approval. The approved DCDM is then compressed, encrypted and packaged for distribution as the Digital Cinema Package (DCP). At the theater, it is unpackaged, decrypted and decompressed to create a DCDM* with images visually indistinguishable from those of the original DCDM. Website: www.dcimovies.com
DCDM See DCI
DCP See DCI
DC-SDI An HD SDI dual link arrangement that is configured to carry live uncompressed DCI-sized 2K footage. That is 2048x1080 pixel images at 24P, with 12-bit 4:4:4 sampling in X'Y'Z' color space. This involves a constant data rate of at least 1913 Mb/s, too much for a single HD-SDI, designed for 1080/60I/30P 10-bit 4:2:2 bit rate of 1248 Mb/s and audio. Hence the use of a dual link. See also: Dual link
DCT (compression) Discrete Cosine Transform - as a basic operation of MPEG video compression it is widely used as the first stage of compression of digital video pictures. DCT operates on blocks (hence DCT blocks) of the picture (usually 8 x 8 pixels) resolving them into frequencies and amplitudes. In itself DCT may not reduce the amount of data but it prepares it for following processes that will. Besides MPEG, JPEG, VC9, WM9 and DV compression depend on DCT. The use of blocks can lead to blocks being visible on screen where data rates that are too low are used. See also: DV, ETSI, JPEG, MPEG-2, MPEG-4, Wavelet
Decibel (dB) Units of measurement expressing ratios of power that use logarithmic scales to give results related to human aural or visual perception. Many different attributes are given to a reference point termed 0 dB - for example a standard level of sound or power with subsequent measurements then being relative to that reference. Many performance levels are quoted in dB - for example signal to noise ratio (S/N). Decibels are given by the expression: 10 log10 P1/P2 where power levels 1 and 2 could be audio, video or any other appropriate values.
Defragmentation See Fragmentation
Deliverables Material that is delivered for use by customers - TV channels, agencies, Web, DVD, mobile phones, etc. The business of making deliverables has expanded with the widening of the scope of digital media. Today it is a considerable business in its own right. Traditionally deliverables have been made as copies from an edited master of programs and commercials. This process involves replaying the master and recording onto the customers' required storage format D5, DVCPRO, HDCAM, etc. It may also involve other treatments such as pan and scan, color grading and standards conversion from say HD 1920 x 1080/60I to SD 720 x 625/50I. If going to mobile phones that have smaller screens with different aspect ratios and supplied by relatively low bandwidth links, then the treatments such as conversion to a lower frame rate, image re-framing and further removal of image detail may be used. The 1080/24P or 25 HD format can be used to make high quality versions for any television format, and even for film. This top-down approach preserves quality as the HD image size means any resizing will be downward, making big pictures smaller, rather than up-res'd blow-ups from smaller pictures. For frame rate conversion, over half a century of running movies on TV has established straightforward ways to fast play 24 f/s material to at 25 f/s and to map it to 60 Hz vertical rates using 3:2 pull-down for television.
For film output, a popular image size is 2K. This is only very slightly wider than 1080-line HD (2048 against 1920 pixels per line), and, for digital exhibition, the same 1080 lines is used. But that material may need further editing, for example, a commercial for showing in a different country may require a new soundtrack and text for pricing. There may be censorship issues so shots need adjusting or replacing. Also the growth of digital media platforms means that more work may be required for a wider deliverables market - with escalating numbers of versions required. Some scenes of a digital film master may need re-grading for domestic TV viewing or further processing to fit the bandwidth and screen limitations of mobile viewing. This type of work may be best undertaken with the finished program in uncommitted form, where the source material and all the tools and their settings are available, so that any part of the program can be re-accessed, changed and the whole program re-output exactly as required for the target medium and without compromising the quality of other deliverables. See also: 3:2 Pull-down, ARC, Down-res, Up-res
Densitometer An instrument used to measure the density of film, usually over small areas of images. The instrument actually operates by measuring the light passing through the film. When measuring movie film density, two sets of color
DiBEG Digital Broadcasting Experts Group, founded September 1997 to drive the growth of digital broadcasting and international contribution by promoting filters are used to measure Status M density for camera negative and intermediate stocks (orange/yellow-based) and Status A for print film to correctly align with the sensiometric requirements of the stocks.
Density The density (D) of a film is expressed as the log of opacity (O). D = Log10 O Using a logarithmic expression is convenient as film opacity has a very wide range and the human sense of brightness is also logarithmic. See also: Film basics.
Depth grading (Stereoscopic) A post production process where negative and positive parallax convergence are adjusted. This is not only a creative tool used to place objects on the Z axis but also a way to ensure that stereoscopic content can be comfortably watched on the screen size it is intended for. For example, in a post suite the director may be viewing a film on a small projection screen but the final delivery format may be a large theatre or IMAX. In practice the eyes have little ability to diverge (up to one degree is considered the rule of thumb) and this is especially a consideration in depth grading for very large screens with positive parallax images, where the distance between the left and right representations of an image may be very widely spaced. Sometimes the term Depth Budget is used to refer to the combined value of positive and negative parallax and expressed as a percentage of screen width. See also: Parallax
DFS Distributed File System - used to build a hierarchical view of multiple file servers and shared files on a network. Instead of having to think of a specific machine name for each set of files, users only need to remember one name as the key to a list of shared files on multiple servers. DFS can route a client to the closest available file server and can also be installed on a cluster for even better performance and reliability. Medium-to-large sized organizations are most likely to benefit from using DFS while smaller ones should be fine with ordinary file servers.
DI See Digital intermediate
Diagnostics Tests to check the correct operation of hardware and software. As digital systems continue to become more complex, built-in automated testing becomes an essential part of the equipment for tests during both manufacture and operation. This involves some extra hardware and software to make the tests operate. Digital systems with such provisions can often be quickly assessed by a trained service engineer, so speeding repair. Remote diagnostics can make use of an Internet connection to monitor and test a product at the customer's site while working from a central service base. Thus expert attention can be used immediately on site. Interdependent multiple systems, such as a video server and its clients, may require simultaneous diagnostics of all major equipment. Here, combining data links from a number of pieces of networked equipment effectively extends the Remote Diagnostics to larger and more complex situations. See also: Diagnostics
the exchange of technical information and international co-operation. It is predominantly made up of Japanese manufacturers and the Japanese Ministry of Posts and Telecoms and has produced ISDB, a specification for digital broadcasting in Japan. See also: ISDB Website: www.dibeg.org
Digital Asset Management (DAM) The management tasks and decisions surrounding the ingestion, annotation, cataloguing, storage, retrieval and distribution of digital assets. The term “digital asset management” (DAM) also refers to the protocol for downloading, renaming, backing up, rating, grouping, archiving, optimizing, maintaining, thinning, and exporting files. Media asset management (MAM) is a sub-category of Digital Asset Management, mainly for audio, video and other media content.
In general the asset being managed is collected and stored in a digital format. There is usually a target version of that referred to as “essence” and is generally the highest resolution and fidelity representation. The asset is detailed by its metadata.
Digital Betacam See: Betacam
Digital Cinema Refers to the digital distribution and projection of cinema material. With nearly all films now using the DI process, the next step is to distribute and replay digital material. Thanks to the DCI's Digital Cinema System Specification (July 2005), a set of standards is in place and many thousands of cinemas have already been converted to digital. Installations started in the USA, and Europe is following. The digital cinema chain includes DCI-compliant equipment for mastering which includes JPEG 2000 encoding and encryption, and players and digital film projectors using usually using DLP, D-ILA and other technologies at the cinemas. These allow high quality viewing on large screens. The lack of all-too-familiar defects such as scratches and film weave - even after a few showings - has its appeal. Besides quality issues, D-cinema introduces potential new digital methods of duplication, security and distribution as well as more flexibility in screening. In addition, stereo cinema (a.k.a. 3D) is easy to set up and present using just one 'film' projector (not two), along with a left and right eye selective viewing system. This is having further implications with trials of live 3D events screened in cinemas creating new business models in the media industry. See also: DCI, DLP-cinema, D-ILA, SXRD
Digital cinematography Shooting movies with digital cameras - not film. This growing practice generally makes use of cameras designed specifically for the purpose. These differ from the television application in that the full range of brightness captured by the image sensors is offered at the output as raw data, allowing color grading, format changes, etc. to be executed as a part of the digital intermediate process. Television cameras are designed to work live, and so they include front-end processing for gamma correction, set-up for the required color look and clipping to suit home viewing conditions. See also: VFR Websites: www.panasonic.com/pbds www.thomsongrassvalley.com/ products/cameras/viper www.red.com www.arri.com
Digital disk recorder (DDR) Disk systems that record digital video and generally intended as drop-in replacements for VTRs or as video caches to provide extra digital video sources for far less cost than a DVTR. They have the advantage of not requiring pre-rolls or spooling but they are not necessarily able to randomly access video frames in realtime. DDRs can also offer the higher data rates needed for uncompressed recordings at an economic price - for SD as well as HD and 2K/4K (film) resolutions. See also: Linear, True random access
Digital intermediate (DI) The DI refers to the process that accepts exposed video or film footage and eventually delivers edited and graded masters, which either can be internegatives for the production labs to generate large numbers of release prints or as digital masters. Initially the term arose to describe a digital version of the traditional chemical intermediate lab where film is graded, cut and copied from camera negative to several interpositives and then to many internegatives. The internegatives are then distributed to the production labs to make the release prints for cinemas. These processes include creating possibly thousands of release prints from a single set of camera negatives. Although the boundaries may vary, generally the DI lab accepts developed camera negative, or data from digital movie/HD cameras, and outputs the edited and graded internegative master for a whole or part of a feature. However, the operational and decision-making processes may differ greatly from the traditional film lab, not least because of the interactive nature of the operation. In the DI lab, decisions become on-screen reality and are seen in full context as they are prepared - no waiting for the 'chemical' lab. Grading, dissolves, cuts and effects can be seen immediately and on a big screen - if needed. The interactive process can be more creative and gives complete confidence that the decisions work well. Also grading can take place after the footage is cut together, so the shots are seen, as graded, in context. The availability of large-scale digital storage means that whole movies can be sent for output to the digital lab's film recorder, exposing 1000ft reels at a time and no final grading required. To help feed the growing number of digital cinemas, the DI lab can produce a DSM (Digital Source Master) - digital cinema's equivalent of internegatives.
Digital keying and chroma keying Digital keying differs from analog chroma keying in that it can key uniquely from any one of the billion colors of component digital video. It is then possible to key from relatively subdued colors, rather than relying on highly saturated colors which can cause color-spill problems on the foreground. A high quality digital chroma keyer examines each of the three components Y, B-Y, R-Y or R, G, B of the picture and generates a linear key for each. These are then combined into a linear key for the final keying operation. The use of three keys allows much greater subtlety of selection than with a chrominance-only key. See also: Chroma keying, Keying
Digital lab A facility where digital intermediate work is carried out.
Digital mixing Digital mixing requires 'scaling' each of two digital signals and then adding them. See also: Binary, Dynamic Rounding
Digital negative Digital image material that contains all the detail (spatial and dynamic/ latitude) held in the original camera negative (OCN) film. This allows all latitude headroom to be included on the material for use in a DI process so adjustments of color and exposure can be made to the same degree as with film. See also: Camera negative
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, acompeting 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
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
DRAM Dynamic RAM. DRAM chips provide high density memories which must be powered and clocked to retain data. Synchronous DRAM (SDRAM) is faster, running up to 200 MHz clockrate. DDRSDRAM is Double Data Rate (DDR) SDRAM and is increasing the performance of many of the newer PC and graphics products. Current available capacities are up to 2 Gb per chip. Their fast access rate has allowed DRAM to replace more expensive SRAM in some applications. DDR 2 increases the data rate and DDR 3 reduces the higher power consumption of DDR 2. There are many more variations and versions to suit specific applications. Development continues.
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 everyminute 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, DVB-SH, has been agreed and awaits standardization by ETSI. It can deliver IP-based media content and data to handheld terminals - phones and PDAs and operates below 3 GHz, typically in the S-band. Terrestrial gap fillers can provide any missing coverage where there is no line-of- sight path to the satellite.
DVB-S (1995) The original DVB forward error coding and modulation standard for satellite television. DVB-S is used for both broadcast network feeds and for direct broadcast satellite services. DVB-S2 (2003) will probably be used for all future new European digital satellite multiplexes, and satellite receivers will be equipped to decode both DVB-S and DVB-S2. Currently its main use is to distribute HDTV. DVB-S2 is based on DVS-S adding two key features: allowing changing encoding parameters in realtime (VCM, Variable Coding and Modulation) and ACM (Adaptive Coding and Modulation) to optimize the transmission parameters for various users for a claimed net performance gain 30 percent.
DVB-T A transmission scheme for digital terrestrial television (DTT). Its specification was approved by ETSI in February 1997 and DVB-T services started in the UK in autumn 1998. As with the other DVB standards, MPEG-2 sound and vision coding are used. It uses Coded Orthogonal Frequency Division Multiplexing (COFDM), which enables it to operate effectively in very strong multipath environments. This means DVB-T can operate an overlapping network of transmitting stations with the same frequency. In the areas of overlap, the weaker of the two received signals is rejected. Where transmitters carry the same programming the overlapping signals provide an area of more reliable reception, known as a signal-frequency network. The DVB digital TV standard is predominant around the world. Notable exceptions are ATSC in the USA, ISDB in Japan, DMB-T/H (Digital Multimedia Broadcast - Terrestrial/Handheld) in China, and T-DMB in South Korea.
DVB-T2 The new extension of the television standard DVB-T, issued by the DVB Group and aims to deliver a minimum 30 percent increase in payload under similar channel conditions. This system transmits compressed digital audio, video, and other data in “physical layer pipes” (PLPs), using OFDM modulation with concatenated channel coding and interleaving. It is currently broadcasting in parts of the UK under the brand name Freeview HD.
DVB over IP Refers to delivery of digital television services (DVB) to homes over broadband IP networks. This could be supplied via cable or, possibly over copper telephone lines using high-speed DSL and the supplier could then achieve the 'triple play' - bundling voice (over-IP) telephone as well as Internet with the television service. This has great potential for interactive television as it includes a built-in fast return link to the service provider. See also: COFDM, IP, IP over DVB Website: www.dvb.org
DVCAM See: DV
DVCPRO See: DV
DVD Digital Versatile Disk - a high-density development of the compact disk. It is the same size as a CD, 12 cm diameter, but stores upwards of 4.38 GB of actual data (seven times CD capacity) on a single-sided, single-layer disk. DVDs can also be double-sided or dual-layer - storing even more data. The capacities commonly available are: DVD-5 Single-side, single-layer 4.38 GB DVD-9 Single-side, dual-layer 7.95 GB DVD-10 Double-sided, single-layer 8.75 GB DVD-18 Double-sided, dual-layer 15.9 GB DVD-5 and DVD-9 are widely used. However the double-sided disks are quite rare, partly because they are more difficult to make and they cannot carry a label. There are various types of DVD including: DVD-R - recordable DVDs with a data capacity of 4.38 GB are popular and low priced. DVD+R - dual layer recordable DVDs with a total capacity of two DVD-Rs. DVD-RAM - re-recordable DVD, re-use up to around 100,000 times. Capacity of 4.38 GB (single-sided). Some new camcorders use these - they offer instant access to shot material and record loop features - useful when waiting to record an event, like a goal, to happen. At home it provides a removable media alternative to VHS. A particular feature is that it can record and replay at the same time.
DVD-Video Combines the DVD with MPEG-2 video compression, with multichannel audio, subtitles and copy protection capability. Multi-channel audio DVD- Video supports PCM, MPEG and Dolby Digital audio, for anything from mono, stereo, Dolby Surround to 5.1 channels. Digital Theatre Sound (DTS) and Sony Dynamic Digital Sound (SDDS) are options. Up to eight separate audio streams can be supported, allowing multiple languages, audio description, director's commentary, etc. For example, a release may have 5.1 Dolby Digital English, two-channel Dolby Digital Spanish with Dolby Surround, and mono French. Region coding Disks can be region- coded and so only play in a particular region (as defined in the player), a set of regions or be 'code-free'. The region numbers are: 1. Canada, US, US Territories 2. Japan, Europe, South Africa, Middle East (including Egypt) 3. Southeast Asia, East Asia (including Hong Kong) 4. Australia, New Zealand, Pacific Islands, Central America, South America, Caribbean 5. Former Soviet Union, Indian Subcontinent, Africa (also North Korea, Mongolia) 6. China See also: HD DVD, Blu-ray Disc, Dolby Digital, Dolby Surround, MPEG-2, MPEG-4
DVE Digital Video Effects (systems). These have been supplied as separate machines but increasingly are being included as an integral part of systems. The list of effects varies but will always include picture manipulations such as zoom and position and may go on to rotations, 3D perspective, page turns, picture bending and curls, blurs, etc. Picture quality and control also vary widely depending on the processing techniques used. See also: Axis, Global D DVTR DVTR - Digital Video Tape Recorder. Sony showed the first DVTR for commercial use in 1986, working to the ITU-R BT.601 component digital video standard and the associated D1 standard for DVTRs. All modern tape recorders are digital and use some form of compressed component video. See also: Betacam SX, D5, D9, DV, DVCPRO, HDCAM
Dynamic range For images - the measurement of the range of brightness in a scene expressed as a ratio or the Log10 of the ratio. Typically a lighting cameraman will try to keep a scene to less than 40:1 (Log = 1.6) to avoid loss of detail in the print. A 100:1 (Log = 2) contrast range in the scene is a typical maximum. See also: Cineon file DE EBU EuropeanBroadcasting Union. An organization comprising European broadcasters which co-ordinates the production and technical interests of European broadcasting. It has within its structure a number of committees which make recommendations to ITU-R. Website: www.ebu.ch