Glossary Of Terms

Disclaimer: this document has been created based upon research gathered from numerous websites (Quantel, SMPTE, etc). This document is not to be considered a definmitive guide or resource. This document has been gerenated as a courtesy of proxivision media. Industry Glossary of Terms A: A/D or ADC Analogue to Digital Conversion. Also referred to as digitization or quantization. The conversion of analogue signals into digital data - normally for subsequent use in a digital machine. For TV, samples of audio and video are taken, the accuracy of the process depending on both the sampling frequency and the resolution of the analogue amplitude information - how many bits are used to describe the analogue levels. For TV pictures 8 or 10 bits are normally used; for sound, 16 or 20 bits are common while 24 bits is also possible. The ITU-R 601 standard defines the sampling of video components based on 13.5 MHz, and AES/EBU defines sampling of 44.1 and 48 kHz for audio. For pictures the samples are called pixels, which contain data for brightness and color. Active Picture The area of a TV frame that carries picture information. Outside the active area there are line and field blanking which roughly, but not exactly, correspond to the areas defined for the original 525 and 625 line analogue systems. In digital TV the blanked/active areas are defined by ITU-R 601, SMPTE RP125 and EBU -E. For both 625 and 525 line formats active line length is 720 luminance samples at 13.5 MHz = 53.3 microseconds. In digital video there are no half lines as there are in analogue. The field blanking is: Format 625/50 525/60 Field 1 24 lines 19 lines Field 2 25 lines 19 lines Active lines/frame 576 487 AES/EBU The Audio Engineering Society (AES) and the EBU together have defined a standard for Digital Audio, now adopted by ANSI (American National Standards Institute). Commonly referred to as 'AES/EBU', this digital audio standard permits a variety of sampling frequencies, for example CDs at 44.1 kHz, or digital VTRs at 48 kHz. 48 kHz is widely used in broadcast TV production. Aliasing Undesirable distortion/effects caused by low sampling frequencies when reproducing an image. Examples are: 1. Temporal aliasing - e.g. vehicle wheel spokes apparently reversing. 2. Raster scan aliasing – Glimmering/Shimmering effects on sharp edges such as horizontal lines. Caused by insufficient filtering this vertical aliasing, and its horizontal equivalent. Aliens A familiar term for alias effects, such as ringing, contouring and jaggy edges caused by lack of resolution in a raster image. Sometimes avoided by filtering or dynamic rounding. Alpha channel Also known in the industry as key channel - a channel to carry a key signal. Glossary of Terms 2 proxivision media

Anamorphic Anamorphic generally refers to the use of 16 x 9 aspect ratio pictures in a 4 x 3 system. For example, anamorphic supplementary lenses are used to change the proportions of an image to 16 x 9 on the surface of a 4 x 3 sensor by either extending the horizontal axis or compressing the vertical. Signals from 16 x 9 cameras and telecines produce an 'anamorphic' signal which is electrically the same as with 4 x 3 images but will appear horizontally squashed if displayed at 4 x 3. The alternative way of carrying 16:9 pictures within 4:3 systems is letterbox. Letterbox has the advantage of showing the correct 16:9 aspect ratio on 4:3 displays; the vertical resolution is less than 16:9 anamorphic. Anti-aliasing Smoothing of aliasing effects by filtering and other techniques. Most, but not all, DVEs and character generators contain anti-aliasing facilities. Application Programming Interface (API) A set of interface definitions (functions, subroutines, data structures or class descriptions) that allow an interface to the functions of a subsystem. They also simplify the work by insulating the application programmer from minutiae of the implementation. Arbitrated Loop A technique used on computer networks to ensure that the network is clear before a fresh message is sent. When it is not carrying data frames the loop carries 'keep-alive' frames. Any node that wants to transmit places its own ID into a 'keep-alive' frame. When it receives that frame back it knows that the loop is clear and that it can send its message. Artifact Particular visible effects directly resulting from technical limitations. Artifacts are generally not described by traditional methods of signal evaluation. For instance, the visual perception of contouring in a picture cannot be described by a signal-to-noise ratio or linearity measurement. ASCII American Standard Code for Information Interchange. This is a standard computer character set used throughout the industry to represent keyboard characters as digital information. There is an ASCII table containing 127 characters covering all the upper and lower case characters in normal and non displayed controls such as carriage return, line feed etc. Variations and extensions of the basic code are used in special applications. ASIC Application Specific Integrated Circuit. A custom designed integrated circuit with functions specifically tailored to a particular application. This effectively replaces the many discrete devices that could otherwise do the job but its performance will be superior. Being far more compact than the separate components, the single chip can work faster than an array of separate chips. Often a ten-fold increase in speed is achieved, while the power consumption can drop by a similar factor and reliability is greatly increased. Glossary of Terms 3 proxivision media

Aspect ratio 1. - of pictures. The ratio of length to height of pictures. Nearly all TV screens are currently 4:3, ie four units across to three units in height but there is a growing move towards widescreen 16:9. Pictures presented this way are believed to absorb more of our attention and have obvious advantages in certain productions, such as sport. In the change towards 16:9 some in-between ratios have been used, such as 14:9. 2. - of pixels. The aspect ratio of the area of a picture described by one pixel. The ITU-R 601 digital coding standard defines luminance pixels that are not square. In the 525/60 format there are 486 active lines each with 720 samples of which 711 may be viewable due to blanking. Therefore the pixel aspect ratio on a 4:3 screen is: • 486/711 x 4/3 = 0.911 (i.e. the pixels are 10% taller than they are wide) For the 625/50 format there are 576 active lines each with 720 samples of which 702 are viewable so the pixel aspect ratio is: • 576/702 x 4/3 = 1.094 (ie the pixels are 9% wider than they are tall) Account must be taken of pixel aspect ratios - for example in executing a DVE move - when rotating a circle, the circle must always remain circular and not become elliptical. Another area where it is important is the movement of images between (standard) computer platforms and television systems. Computers nearly always use square pixels so their aspect ratio must be adjusted to suit television. This process takes time and will not be perfect and the quality of the result will depend on the quality of the processing used. ATM Asynchronous Transfer Mode. A high speed switched data communications system capable of both local area network (LAN) and wide area network (WAN) operation. Website: www.atmforum.com ATSC The (US) Advanced Television Systems Committee. Established in 1982 to co-ordinate the development of voluntary national technical standards for the generation, distribution and reception of high definition television. In 1995 the ATSC published \"The Digital Television Standard\" which describes the US Advanced Television System. This uses MPEG-2 compression for the video and AC-3 for the audio and includes a wide range of video resolutions (as described in ATSC Table 3) and audio services (Table 2). It uses 8 and 16 VSB modulation respectively for terrestrial and cable transmission. Website: www.atsc.org ATV Advanced Television; Television with capabilities beyond greater than analogue NTSC, i.e. digital television (DTV) and high definition (HDTV). Auditory Masking The psycho-acoustic phenomenon of human hearing where what can be heard is affected by the components of the sound. For example, a loud sound will mask a soft sound close to it in frequency. Audio compression systems such as Dolby Digital and MPEG audio use auditory masking as their basis and only code what can be heard by the human ear. Glossary of Terms 4 proxivision media

Axis (x, y, z) Used to describe the three-dimensional axes available in DVE manipulations. At normal (clear) x lies across the screen left to right, y up the screen bottom to top and z points into the screen. Depending on the power of the equipment and the complexity of the DVE move, several sets of xyz axes may be in use at one time. For example, one set may be referred to the screen, another to the picture and a third offset to some point in space (reference axis). B: Background task Operation or tasked that is performed and completed while the main operation continues uninterrupted. Background tasks have the greatest use during pressured situations, such as during live programming and transmission. Bandwidth The amount of information that can be passed in a given time. In television a large bandwidth is needed to show sharp picture detail and so is a factor in the quality of recorded or transmitted images. ITU-R 601 and SMPTE RP 125 allow analogue luminance bandwidth of 5.5 MHz and chrominance bandwidth of 2.75 MHz, the highest quality attainable in any standard broadcast format. Digital image systems generally require large bandwidths hence the reason why many storage and transmission systems revert to compression techniques to accommodate the signal. Betacam Developed by Sony, Betacam is an analogue component VTR system using a 1.25-inch cassette; similar to the Betamax. Although recording the Y, R-Y and B-Y component signals onto tape many machines are operated with coded (PAL or NTSC) video in and out. The system has continued to be developed over the years to offer models for the industrial and professional markets as well as full luminance bandwidth (Betacam SP), PCM audio and SDI connections. Digital versions exist such as the high-end Digital Betacam and Betacam SX. Betacam SX A digital tape recording format developed by Sony which uses a constrained version of MPEG-2 compression at the 4:2:2 profile, Main Level (422P@ML) using 1¼2-inch tape cassettes. Binary Mathematical representation of a number to base 2, ie with only two states, 1 and 0; on and off; or high and low. This is the base of the mathematics used in digital systems and computing. Binary representation requires a greater number of digits than the base 10 decimal system most of us commonly use everyday. For example the base 10 number 254 is 11111110 in binary. The result of a binary multiplication contains the sum of digits of the original numbers. So; Plain-Text: 10101111 x 11010100 = 1001000011101100 (In decimal 175 x 212 = 37,100) Each digit is known as a bit. This example multiplies two 8-bit numbers and the result is always a 16-bit number. Multiplication is a very common process in digital television equipment. Glossary of Terms 5 proxivision media

BIOS The BIOS runs off the onboard flash memory when the computer is powered on and it initializes the chipset and the memory subsystem. Subsequently, it uncompresses itself from flash memory into the system main memory and starts executing from there. PC BIOS code also contains diagnostics to assure critical hardware components, such as keyboard, disk drive, I/O ports etc., are operational, and properly initialized. Nearly all BIOS implementations can optionally execute a setup program interfacing the nonvolatile BIOS memory (CMOS). This memory holds user- customizable configuration data (time, date, hard drive details, etc.) accessed by BIOS code. In most modern BIOS implementations, one can select what boots first: CD, hard disk, floppy disk, flash keydrive and so on. This is particularly useful for installing operating systems or booting to LiveCDs, and for selecting the order of testing for the presence of bootable media. Some BIOS allow the user to select the operating system to load (e.g. load another OS from the second hard disk), though this is more often handled by a second-stage boot loader. Bit (B) Binary digit = 1 bit One mathematical bit can define two levels or states, on or off, black or white, 0 or 1 etc; - two bits can define four levels, three bits eight, and so on: generally 2n, where n = the number of bits. In image terms eight bits can define 256 levels of brightness from black to white. Bitstream A flow of data. Bi-directional Picture Method used in compressing video. B frames are encoded much like Predictive frames (see later in glossary) except that the prediction is done from a combination of a previous P or I frame, and a future frame P or I frame. The results are then averaged to represent the current frame. This is called bi-directional prediction. The prediction relative to future frames is needed to capture a new object that may appear in the video in the middle of the group of pictures. Bridge In computer networking terms a bridge is a stand-alone device or specially configured computer that connects different LANs, and allows them to act as segments of one LAN. Bridges only operate at OSI Layer2, meaning that it cannot alter the data being transferred. Browse Term used when viewing “Browsing” still stores, graphics systems and disk-based video stores to display a selection of reduced sized images (a.k.a. “Thumbnails” “Proxies”) to aid choice of stored clips or stills. For moving video a timeline may be available so clips can be shuttled allowing the full sized images brought to use pre-cued. Bug An error in a computer program that causes the system to behave erratically, incorrectly or to stop altogether. This term originates from the era of the original computers that utilized tubes and relays; real “live” bugs were attracted by the heat and light and used to infest the internal works. Bus An internal pathway for sending digital signals from one part of a system to another. Glossary of Terms 6 proxivision media

BWF Broadcast WAV - an audio file format based on Microsoft's WAV. It can carry PCM or MPEG encoded audio and adds the metadata, such as a description, originator, date and coding history, needed for interchange between broadcasters. Byte (B), Kilobyte (kB), Megabyte (MB), Gigabyte (GB), Terabyte (TB) and Petabyte (PB) 1 Byte (B) = 8 bits (B) which can describe 256 discrete values (brightness, color, etc.) Traditionally, just as computer-folk like to start counting from zero, they also ascribe 2 raised to the power 10, 20, 30 etc (210, 220, 230 etc) to the values kilo, mega, giga, etc. which become, 1,024, 1,048,576, 1,073,741,824 etc. This can be difficult to handle for those drilled only in base- 10 mathematics. Fortunately, disk drive manufacturers today now describe storage capacity in powers of 10, so a 9 GB drive has 9,000,000,000 bytes capacity. Byte: A contiguous sequence of a fixed number of bits, generally eight; also know as an “octet”. An 8 eight-bit byte can hold 256 possible values (2 = 256). C: CCD Charge Coupled Device (CCD) - either assembled as a linear or two-dimensional array of light sensitive elements. Light is converted to an electrical charge proportional to the light impinging on each cell. The cells are coupled to a scanning system which, after analogue to digital conversion, presents the image as a series of binary digits. Early CCD arrays were unable to reproduce a wide range of brightness but they now offer low noise, high resolution imaging up to HDTV level. CCIR Comité Consultatif International des Radiocommunications. This has been absorbed into the ITU under ITU-R. CCITT International Telegraph and Telephone Consultative Committee. As the name suggests this was initially set up to establish standards for the telephone industry in Europe. It has now been superseded by ITU-T so putting both radio frequency matters (ITU-R) and telecommunications under one overall United Nations body. CDDI Copper Data Distributed Interface. A high-speed data interface - like FDDI but using copper. CDTV Conventional Definition Television. The analogue NTSC, PAL, SECAM television system with normal 4:3 aspect ratio pictures. Checksum A simple check value of a block of data, calculated by adding all the bytes in a block. It is fairly easily fooled by typical errors in data transmission systems, so that for most applications a more sophisticated system such as CRC is preferred. Glossary of Terms 7 proxivision media

Chroma keying The process of overlaying one video signal over another, the areas of overlay being defined by a specific range of color, or chrominance, on the foreground signal. For this to work reliably, the chrominance must have sufficient resolution, or bandwidth. PAL or NTSC coding systems restrict chroma bandwidth and so are of very limited use for making a chroma key which, for many years, was restricted to using live, RGB camera feeds. An objective of the ITU-R 601 digital sampling standard was to allow high quality chroma keying in postproduction. The 4:2:2 sampling system allowed far greater bandwidth for chroma than PAL or NTSC and helped chroma keying, and the whole business of layering, to thrive in post production. High signal quality is still important and anything but very mild compression tends to result in keying errors appearing - especially at DCT block boundaries. Chroma keying techniques have continued to advance and use many refinements, to the point where totally convincing composites can be easily created. You can no longer \"see the join\" and it may no longer be possible to distinguish between what is real and what is keyed. Chroma Subsampling Summarized: In digital image processing, chroma subsampling is the use of lower resolution for the color (chroma) information in an image than for the brightness (intensity or luma) information. It is used when an analog component video or YUV signal is digitally sampled. Because the human eye is less sensitive to color than intensity, the chroma components of an image need not be as well defined as the luma component, so many video systems sample the color difference channels at a lower definition (i.e., sample frequency) than the brightness. This reduces the overall bandwidth of the video signal without apparent loss of picture quality. The missing values will be interpolated or repeated from the preceding sample for that channel. The subsampling in a video system is usually expressed as a three part ratio. The three terms of the ratio are: the number of brightness (\"luminance\" \"luma\" or Y) samples, followed by the number of samples of the two color (\"chroma\") components: U/Cb then V/Cr, for each complete sample area. For quality comparison, only the ratio between those values is important, so 4:4:4 could easily be called 1:1:1; however, traditionally the value for brightness is always 4, with the rest of the values scaled accordingly. Sometimes, four part relations are written, like 4:2:2:4. In these cases, the fourth number means the sampling frequency ratio of a key channel. In virtually all cases, that number will be 4, since high quality is very desirable in keying applications. Note: The mapping examples given are only theoretical and for illustration. The bitstreams of real- life implementations will probably differ. Glossary of Terms 8 proxivision media

Chrominance The color part of a signal, relating to the hue and saturation but not to the brightness or luminance of the signal. Thus black, grey and white have no chrominance, but any colored signal has both chrominance and luminance. Although imaging equipment registers red, blue and green the television picture is handled and transmitted as U and V, I and Q, Cr and Cb, (R-Y) and (B-Y) which all represent the chrominance information of a signal. Clip The name is taken from the film industry and refers to a segment of sequential frames made during the filming of a scene. In television terms a clip is the same but represents a segment of video frames. Clip Pack A multi-layer clip constructed in editing systems. Clone An exact copy, indistinguishable from the original. As in copying recorded material, e.g. copy of a non-compressed recording to another non-compressed recording. If attempting to clone compressed material care must be taken not to decompress it as part of the process or the result will not be a clone. Codec A Codec is a portmanteau of either \"Compressor-Decompressor\" or \"Coder-Decoder,\" which describes a device or program capable of performing transformations on a data stream or signal. Codecs can both put the stream or signal into an encoded form (often for transmission, storage or encryption) and then retrieve, or decode that form for viewing or manipulation in a format more appropriate for these operations. Codecs are often used in streaming media solutions. The raw encoded form of audio and video data is often called essence, to distinguish it from the metadata information that together make up the information content of the stream and any \"wrapper\" data that is then added to aid access to or improve the robustness of the stream. Many multimedia data streams need to contain both audio and video data, and often some form of metadata that permits synchronization of the audio and video. Each of these three streams may be handled by different programs, processes, or hardware; but for the multimedia data stream to be useful in stored or transmitted form, they must be encapsulated together. This function is carried out by a video file format (or container), such as *.mpg, *.avi, *.mov, *.mp4, *.rm, *.ogg or *.tta. Some of these formats are limited to containing streams conforming to a small fixed set of codecs, while others are intended to be more general purpose. COFDM A transmission scheme proposed for DVB in Europe based on Coded Orthogonal Frequency Division Multiplexing. It allows for the use of either 1705 carriers (usually known as '2k'), or 6817 carriers ('8k'). Concatenated error correcting is used. The '2k' mode is suitable for single transmitter operation and for relatively small single-frequency networks with limited transmitter power. The '8k' mode can be used both for single transmitter operation and for large area single- frequency networks. The guard interval is selectable. The '8k' system is compatible with the '2k' system. Glossary of Terms 9 proxivision media

Color space The color range between specified references; typically three references are quoted in television: RGB, Y, R-Y, B-Y and Hue Saturation and Luminance (HSL). In print, Cyan, Magenta, Yellow and Black (CMYK) are used. Moving pictures between these is possible but requires careful attention to the accuracy of processing involved. Operating across the media - print, film and TV, as well as between computers and TV equipment - will require conversions in color space. Component (video) The normal interpretation of a component video signal is one in which the luminance and chrominance remain as separate components, eg analogue components in MII and Betacam VTRs, digital components Y, Cr, Cb in ITU-R 601. RGB is also a component signal. Component video signals retain maximum luminance and chrominance bandwidth. Composite (video) Luminance and chrominance are combined along with the timing reference 'sync' information using one of the coding standards - NTSC, PAL or SECAM - to make composite video. The process, which is an analogue form of video compression, restricts the bandwidths (image detail) of components. In the composite result color is literally added to the monochrome (luminance) information using a visually acceptable technique. As our eyes have far more luminance resolving power than for color, the color sharpness (bandwidth) of the coded single is reduced to far below that of the luminance. This provides a good solution for transmission but it becomes difficult, if not impossible, to accurately reverse the process (decode) into pure luminance and chrominance which limits its use in post-production. Compositing Simultaneous multi-layering and design for moving pictures. Modern designs often use many techniques together, such as painting, retouching, rotoscoping, keying/matting, digital effects and color correction as well as multi-layering to create complex animations and opticals for promotions, title sequences and commercials as well as in program content. Besides the creative element there are other important applications for compositing equipment such as image repair, glass painting and wire removal - especially in motion pictures. The quality of the finished work, and therefore the equipment, can be crucial especially where seamless results are demanded. For example, adding a foreground convincingly over a background - placing an actor into a scene - without any telltale blue edges or other signs that the scene is composed. Compression (audio) Reduction of bandwidth or data rate for audio. Many digital schemes are in use, all of which make use of the way the ear hears (e.g. that a loud sound will tend to mask a quieter one) to reduce the information sent. Generally this is to benefit in areas where bandwidth and storage are limited, such as in delivery systems to the home. Compression (video) Method used when reducing the bandwidth or data rate of a video stream. Analogue broadcast standards used today: PAL, NTSC and SECAM are, in fact, compression systems which reduce the data content of their original RGB sources. Glossary of Terms 10 proxivision media

Compression ratio A term meaning the ratio of the data in the non-compressed digital video signal versus the compressed version. Modern compression techniques start with the component television signal but a variety of sampling ratios are used, 4:2:2, 4:2:0 (MPEG-2), 4:1:1 (DVCPRO), etc. The ratio should not be used as the only method to assess the quality of a compressed signal. For a given technique greater compression can be expected to result in worse quality but different techniques give widely differing quality of results for the same compression ratio. The only sure method of judgment is to make a very close inspection of the resulting pictures. Concatenation Defined as the linking together of different proprietary systems. In digital television this refers to the concatenation of compression systems which is currently a subject of concern because any compression beyond about 2:1 results in the removal of information that cannot be recovered. As the use of compression increases, so too does the likelihood that material will undergo a number of compressions between acquisition and transmission. Although the effects of one compression might not be very noticeable, the impact of multiple decompressions and recompressions - with the material returned to baseband in between - can cause considerable damage. Damage is the greatest when different compression schemas are concatenated in a particular signal path. Conditional access Digital Television signals can be scrambled in such a way that they cannot be understood by a conventional decoder. Only when de-scrambled can the original pictures be seen by the viewer. By controlling the operation of the de-scrambling system through the use of a pre-paid access card, or by a transmitted code, the broadcaster can control access to a particular channel or service. An example of conditional access is Pay-per-View. Conform Making the final edit according to a prepared scheme such as an Edit Decision List. EDLs can be used to directly control conforming in an on-line edit suite (auto-conforming). The time to conform varies widely, from a tape suite which takes much longer than the finished program running time, to a disk-based true random access suite that reduces time by loading material in C-mode, conforming itself takes only a moment and still allows any adjustments to be easily made. Control track A linear track recorded onto videotape at frame frequency as a reference for the running speed of a VTR, for the positioning or reading of the video tracks and to drive a tape counter. It is a magnetic equivalent of sprocket holes in film. One of the main purposes of striping tapes is to record a continuous control track for the pictures and audio to be added later - as in insert editing. Control tracks are not used in disk recording and editing. Glossary of Terms 11 proxivision media

Co-sited sampling A sampling technique that is applied to color difference component video signals (Y, Cr, Cb) where the color difference signals, Cr and Cb, are sampled at a sub-multiple of the luminance, Y, frequency - for example as in 4:2:2. If co-sited sampling is applied, the two color difference signals are sampled at the same instant, and simultaneously with one of the luminance samples. Co-sited sampling is the 'norm' for component video as it ensures the luminance and the chrominance digital information is coincident, minimizing chroma/luma delay. Consolidation The clearing of space on a computer storage disk to allow consistent recording. This generally involves the moving of fragmented data on the disks to one area, leaving the remainder free so that recording can proceed without having to make random accesses. The larger the amount of data stored, the longer consolidation may take. Careful consideration must be given to large capacity multi-user systems, such as video servers. Note: The need for consolidation arises because of the store's inability to continuously record television frames randomly at video rate. A true random access store has no need of consolidation. Glossary of Terms 12 proxivision media

Constant Bit Rate The term constant bit rate (CBR) is a term in telecommunications Quality of Service. Compare with variable bit rate. When referring to codecs, constant bit rate encoding means that the rate at which a codec's output data should be consumed is constant. CBR is useful for streaming multimedia content on limited capacity channels since it is the maximum bit rate that matters, not the average, so CBR would be used to take advantage of all of the capacity. CBR would not be the optimal choice for storage as it would not allocate enough data for complex sections (resulting in degraded quality) while wasting data on simple sections. Most coding schemes such as Huffman coding or run-length encoding produce variable-length codes, making perfect CBR difficult to achieve. This is partly solved by varying the quantization (quality), and fully solved by the use of padding. (However, CBR is implied in a simple scheme like reducing all 16-bit audio samples to 8-bits.) Contouring An unwanted artifact similar to posterization. Digital systems exhibit contouring when insufficient quantizing levels are used or inaccurate processing, or truncation occurs. Corner pinning A technique for defining the position and rotation of pictures in a DVE, by dragging their corners to fit a background scene. For example to fit a (DVE) picture into a frame hanging on a wall. Corner pinning was developed by Quantel as an alternative to precisely setting the many parameters needed to accurately position a picture in 3D space. It can also be combined with the data derived from four-point image tracking to substitute objects in moving images, for example replacing the license plate on a moving vehicle. CRC Cyclic Redundancy Check - an advanced checksum technique. It uses a check value calculated for a data stream by feeding it through a shifter with feedback terms 'EXORed' back in. It performs the same function as a checksum but is considerably harder to fool. A CRC can detect errors but not repair them, unlike an ECC. A CRC is attached to almost any burst of data which might possibly be corrupted. On disks any error detected by a CRC is corrected by an ECC. ITU- R 601 data is subjected to CRCs, if an error is found the data is concealed by repeating appropriate adjacent data, also Ethernet packets use CRCs etc. CRF Cutting Room Floor. Moving material to CRF in Quantel editing systems removes it from the work area - but not from the disk store. CSDI Compressed Serial Data Interface - in the process of being ratified by the SMPTE. It uses the same signal format as DVCPRO and, as this is a compressed format, enables video data to be transferred at four times real time rate over SDI links. Glossary of Terms 13 proxivision media

Cut (edit) A transition at a frame boundary from one clip to another. On tape a cut edit is performed by recording (dubbing) the new clip at the out-point of the last, whereas with true random access editing no re-recording is required - there is simply an instruction to read frames in a new order. Simple non-linear disk systems may need to shuffle their recorded data in order to achieve the required frame-to-frame access for continuous replay The editable frame boundaries may be restricted by video coding systems, PAL, NTSC, SECAM and MPEG. Non-compressed component video and that compressed using only intra-frame compression (eg motion JPEG) can be edited on any frame boundary without additional processing. D: D1 A format for digital video tape recording working to the ITU-R 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. Being a component recording system it is ideal for studio or post production work with its high chrominance bandwidth allowing excellent chroma keying. Also multiple generations are possible with very little degradation and D1 equipment can integrate without transcoding to most digital effects systems, telecines, graphics devices, disk recorders, etc. Being component there are no color framing requirements. Despite the advantages, D1 equipment is not extensively used in general areas of TV production, at least partly due to its high cost. D2 The VTR standard for digital composite (coded) PAL or NTSC signals. It uses 19 mm tape and records approx 208 minutes on a single cassette. D2 is considered a direct replacement for 1-inch analogue VTRs. Though offering good stunt modes and multiple generations with low losses, it is none-the-less a coded system, therefore coded characteristics are present. Users of D2 should be conscious of transcoding footprints, low chrominance bandwidths and color framing sequences. D2 employs an 8-bit format to sample the whole coded signal; meaning results are more susceptible to contouring artifacts. Glossary of Terms 14 proxivision media

D3 A VTR standard using 1¼2-inch tape cassettes for recording digitized composite (coded) PAL or NTSC signals sampled at 8 bits. Cassettes are available for 50 to 245 minutes. Since this uses a composite signal the characteristics are generally as for D2 except that the 1¼2-inch cassette size has allowed a full family of VTR equipment to be realized in one format, including a camcorder. 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 component signals sampled to ITU-R 601 recommendations at 10-bit resolution. Being a non-compressed component digital video recorder means D5 enjoys 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 also has provision for HDTV recording at approx 4:1 compression (HD D5). D6 A digital tape format which uses a 19mm helical-scan cassette tape to record uncompressed High Definition Television material at 1.88 GB/s. D6 is currently the only recognized HD format. D6 accepts both the European 1250/50 interlaced format and the Japanese 260M version of the 1125/60 interlaced format which uses 1035 active lines. It does not accept the ITU format of 1080 active lines. ANSI/SMPTE 277M and 278M are D6 standards. D7 This has been assigned to DVCRPO. D16 A recording format for digital film images making use of standard D1 recorders. The scheme was developed specifically to handle Quantel's Domino (Digital Opticals for Movies) pictures and record them over the space that sixteen 625 line digital pictures would occupy. This way three film frames can be recorded or played every two seconds. Playing the recorder allows the film images to be viewed on a standard monitor; running at x16 speed shows full motion direct from the tape. Database A database is a collection of records stored in a computer in a systematic way, such that a computer program can consult it to answer questions. For better retrieval and sorting, each record is usually organized as a set of data elements (facts). The items retrieved in answer to queries become information that can be used to make decisions. The computer program used to manage and query a database is known as a database management system (DBMS). Glossary of Terms 15 proxivision media

Data Packet (Packet) A chunk of data transmitted over a packet-switching network. Packet-switching is any protocol in which data is broken up into these packets and can then follow various routes to its destination – different packets which together comprise one message may travel via different paths and are assembled when they arrive. Packets therefore, of necessity, contain a destination address as well as the data to be transmitted. Packets are often confused with \"frames\"; frames are the data structures used by the physical network hardware to move the data. Information that needs to be sent is parceled up into a packet by the computer, and the packets are parceled up by the network hardware into frames. 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. This compares with 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. DCT (compression) Discrete Cosine Transform - widely-used as the first stage of compression of digital video pictures. DCT operates on blocks of the picture (usually 8 x 8 pixels) resolving them into frequencies, amplitudes and colors. In itself DCT may not reduce the amount of data but it prepares it for following processes that will. JPEG and MPEG depend on DCT. DD2 Using D2 tape, data recorders have been developed offering vast storage of data. A choice of data transfer rates is available to suit computer interfaces. Like other computer storage media, images are not directly viewable, and editing is difficult. Decibel (dB) Units of measurement expressing ratios using 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 - subsequent measurements then being relative to that reference. Many performance levels are quoted in dB. Dedicated hardware Hardware and software built for a specific task (eg a DVE), not general purpose (computer). Dedicated hardware gives much improved processing speeds, between 10 and 100 fold, over systems using the same technology applied to general purpose architecture and operating system software. This becomes important in image processing where tasks require a great deal of power, an important point for working with HDTV. 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. Some extra hardware and software has to be added to make the tests operate. Digital systems with such provisions can often be quickly assessed by a trained service engineer, so speeding repair. Glossary of Terms 16 proxivision media

Digital Betacam An evolution of the original analogue Betacam VTR that records digitally on a Betacam-style cassette. Betacam utilizes mild intra-field compression to reduce the ITU-R 601 sampled video data by about 2:1. Some models can replay both digital and analogue Betacam cassettes. Digital Disk Recorder (DDR) Disk systems that record digital video. Their application is often as a replacement for a VTR 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 their operation is not true random access. Digital keying and chroma keying Digital chroma keying differs from analogue in that it can key uniquely from any one of the 16 million 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) of the picture and generates a linear key for each. These are then combined into a composite linear key for the final keying operation. The use of three keys allows much greater subtlety of selection than with a chrominance-only key. Digital mixing Digital mixing requires 'scaling' each of two digital signals and then adding them. Mathematically this can be shown as: A x K = (Mix) 1 B x (1-K) = (Mix) 2 Result = (Mix) 1 + (Mix) 2 Where A and B represent the two TV signals, and K the positional coefficient or value at any point of the mix. In a digital system, K will also be a number, normally an 8-bit value, to provide a smooth mix or dissolve. When two 8-bit numbers are multiplied together, the result is a 16-bit number. When mixing, it is important to add the two 16-bit numbers to obtain an accurate result. This result must then be truncated or rounded to 8 bits for transmission to other parts of the digital system. Truncation by simply dropping the lower bits of the partial result (Mix) 1 or (Mix) 2, to 10 bits, or even 12 or 14 bits, will introduce inaccuracies. Hence it is important that all partial results, eg (Mix) 1 and (Mix) 2, maintain 16-bit resolution. The final rounding of the result to 8 bits can reveal visible 1-bit artifacts - but these can be avoided with Dynamic Rounding. Digital S A 1.25-inch digital tape format that 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 search up to x 32 speed. Video sampled at 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. Glossary of Terms 17 proxivision media

Digitizer A system that converts an analogue input to a digital representation. Examples include analogue to digital converters (ADCs), mouse and touch tablet, each are systems that take a spatial measurement and present it to a computer in a digital format. Digitizing time Time taken to record footage into a disk-based editing system. The name suggests the material is being played from an analogue source, which, with the use of DVTRs, is not necessarily the case. Digitizing time is often regarded as “dead-time” but it need not be. It can be reduced if some initial selection of footage has been made, e.g. logging. Direct Editing Editing at a workstation which directly edits material stored in a server. For this the workstation does not need large-scale video and audio storage but depends totally on the server store. The arrangement allows background loading of new material, via several ports if required, and playout of finished results, while removing the need to duplicate storage or transfer material to/from the workstation and allowing any number of connected workstations to share work. The efficiency of direct editing allows fast throughput and is attractive to news as well as post production This depends on a server that can act as an edit store as well as a powerful interface to the edit workstation. Quantel's edit systems and Clipbox video server can operate this way. Discrete 5.1 Audio This reproduces six separate (discrete) channels - Left, Centre, Right, Left Rear, Right Rear and sub-woofer. All the five main channels have full frequency response that, together with a separate low-frequency sub-woofer, creates a three-dimensional effect. Glossary of Terms 18 proxivision media

Dither In digital television, analogue original pictures are converted to digits: a continuous range of luminance and chrominance values are translated into a set range of numbers. While some analogue values will correspond exactly to numbers, others will, inevitably, fall in between. Given that there will always be some degree of noise in the analogue original signal the numbers may dither by one Least Significant Bit (LSB) between the two nearest values. This has the advantage of allowing the digital system to describe analogue values between LSBs to give a very accurate digital rendition of the analogue world. If the image is produced by a computer, or as the result of digital processing, the dither may not exist - leading to contouring effects. With the use of Dynamic Rounding dither can be added to pictures to give a more accurate result. 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 35mm 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 analogue Dolby Surround for Pro Logic playback. Dolby Surround, Dolby Stereo, Dolby 4:2:4 Matrix Analogue coding of four audio channels - Left, Centre, 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 are used to steer the audio and increase channel separation. The Dolby Surround system, originally developed for the cinema, is a method of getting more audio channels but suffers from poor channel separation, a mono limited bandwidth surround channel and other limitations. A Dolby Surround track can be carried by analogue audio or linear PCM, Dolby Digital and MPEG compression systems. Glossary of Terms 19 proxivision media

Dominance Field dominance defines whether a field type 1 or type 2 represents the start of a new 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 to the opposite way to the recording can cause a juddery image display. Much equipment, including Quantel's, allows the selection of field dominance and can handle either. DRAM Dynamic RAM (Random Access Memory). High density, cost-effective memory chips (integrated circuits). Their importance is such that the Japanese call them the 'rice of electronics'. DRAMs are used extensively in computers and generally in digital circuit design. In digital video equipment they make up stores to hold pictures. Being solid state there are no moving parts and they offer the fastest access for data. Each bit is stored on a single transistor, and the chip must be powered and clocked to retain data. Current sizes available are 16 and 64 Mb (per chip), with 256 Mb now becoming commercially available. Development continues with plans to produce 1 GB chips early in the next century. Such projects require the use of x-ray lithography with chip features smaller than a micrometer - some 1000 times narrower than a human hair. Drop-frame (timecode) The 525/60 line/field format used with the NTSC color coding system does not run at exactly 60 fields per second but 59.94, or 29.97 frames per second - a difference of 1:1000. Timecode identifies 30 frames per second. Drop-frame timecode compensates by dropping two frames at every minute except the tenth. Note that the 625/50 PAL system is exact and does not require drop-frame. DSS Digital Satellite Service. The term used to describe DTV services distributed via satellite. DTT Digital Terrestrial Television. The term used in Europe to describe the broadcast of digital television services using terrestrial frequencies. DTV Digital Television - everything that can be broadcast to the home digitally whether by cable, satellite or terrestrially. Although the signals produced by converting analogue pictures into their digital equivalent - digitizing - actually increases their bandwidth, they are then available for digital compression which can easily reduce four signals into the space of one analogue channel, while still maintaining acceptable levels of quality. Services such as video on demand (VOD) resort to heavy compression to pack many feeds into one channel so that any selected movie can be on the cable within a tightly specified time-frame. There is a price to pay: the heavier the compression, the poorer the pictures. As well as current line rates, field rates and aspect ratios, DTV is taken to include 16:9 and the higher resolution standards of HDTV. For the US these are all described in the ATSC's table 3. Data can also be delivered. Glossary of Terms 20 proxivision media

Dublin Core: The Dublin Core is a metadata standard for describing digital objects (including webpages) to enhance visibility, accessibility and interoperability, often encoded in XML. It was so named because the first meeting of metadata and web specialists which saw its birth was held in the town of Dublin (division of Columbus), Ohio in the USA The Dublin Core Metadata Element Set, part of the Dublin Core Metadata Initiative (DCMI), consists of 15 optional metadata elements, any of which could be repeated or omitted. 1. Title 2. Creator 3. Subject 4. Description 5. Publisher 6. Contributor 7. Date 8. Type 9. Format 10. Identifier 11. Source 12. Language 13. Relation 14. Coverage 15. Rights Duplex: In computer communications, there are three kinds of connection between two devices: • Simplex: In which data can only flow one way. • Half duplex: Data can flow either way, but only one way at a time. • Full duplex: allows data flow in both directions at once. Ethernet supports full duplex operation, but only between two devices over twisted pair cables. Regular 10BaseT or 100BaseT cable has two physical pairs of wires in it, which in full duplex operation can be used for full bandwidth data transfer in both directions – one wire pair per direction. This works because when there are only two devices involved, so collisions are impossible. The second wire pair is normally needed for collision detection. DV This digital VCR format is a co-operation between Hitachi, JVC, Sony, Matsushita, Mitsubishi, Philips, Sanyo, Sharp, Thomson and Toshiba. It uses 6.35 mm (0.25-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 models 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 minutes standard cassette (125 x 78 x 14.6 mm) or smaller 1 hour 'mini' cassette (66 x 48 x 12.2 mm). The video recording rate is 25 Mb/s. DVB Digital Video Broadcasting Glossary of Terms 21 proxivision media

DVB-T The DVB-T is a transmission scheme for terrestrial digital television. As with the other DVB standards, MPEG-2 sound and vision coding form the basis of DVB-T. It uses a transmission scheme based on Coded Orthogonal Frequency Division Multiplexing (COFDM), which spreads the signals over a large number of carriers to enable it to operate effectively in very strong multipath environments. DVCAM Sony's development of native DV which records a 15micron (15x10 -6 m, fifteen thousandths of a millimetre) track on a metal evaporated (ME) tape. DVCAM uses DV compression of a 4:2:0 signal for 625/50 (PAL) sources and 4:1:1 for 525/60 (NTSC). Audio is recorded in one of two forms - four 12-bit channels sampled at 32 kHz, or two 16-bit channels sampled at 48 kHz. DVCPRO Panasonic's development of native DV which records a 18 micron (18x10<sup>-6</sup>m, eighteen thousandths of a millimetre) track on metal particle tape. DVCPRO uses native DV compression at 5:1 from a 4:1:1 8-bit sampled source. It uses 12 tracks per frame for 625/50 sources and 10 tracks per frame for 525/60 sources, both use 4:1:1 sampling. Tape speed is 33.813mm/s. It includes two 16-bit digital audio channels sampled at 48 kHz and an analogue cue track. Both Linear (LTC) and Vertical Interval Time Code (VITC) are supported. DVCPRO 50 This variant of DV uses a video data rate of 50 Mb/s - double that of other DV systems - and is aimed at the higher quality end of the market. Sampling is 4:2:2 to give enhanced chroma resolution, useful in post production processes (eg chroma keying). Four 16-bit audio tracks are provided. DVD Digital Versatile Disk - a high density development of the earlier Compact Disk. It is the same size as a CD but stores from 4.38 GB (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: • 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 \"Blu-ray\", a new format for DVD, uses a blue laser instead of the traditional red laser currently employed in most CD and DVD players. This blue laser allows 27 gigabytes of data to be stored on a single layer of one side of a disc, compared with a maximum capacity of around 4.38 gigabytes per layer on a standard DVD. DVD-Video DVD-Video combines the DVD optical disk with MPEG-2 video compression, has multiple multi- channel audio tracks, subtitles and copy protection capability for recording video on a CD-sized disk. To maximize quality and playing time DVD-Video movies use Variable Bit Rate (VBR) MPEG-2 coding where the bit rate varies with the demands of the material. A typical 525/60 TV format, 24fps movie would have an average bit rate of 3.5 Mb/s, but for sections with a great deal of movement it could peak at 8 or 9 Mb/s. For a 30 fps telecined result of 24fps movie material only 24 fps are coded onto the disk, the 3:2 pulldown conversion back to 30 fps being performed in the player. This allows a 120 minute 24 fps movie to fit on a DVD-5. Glossary of Terms 22 proxivision media

RSDL Reverse Spiral Dual Layer - For continuous playback of long movies dual layer DVD-9 disks can employ a 'reverse spiral' technique so that the second layer starts where the first layer ends. This layer transition is supported by all DVD-Video players. 16:9 Widescreen DVD - Video is the first domestic format natively to support anamorphic 16:9 video, producing pictures with full vertical resolution on 16:9 widescreen TV sets. Previously, widescreen pictures would have been letterboxed within a 4:3 video frame and then magnified by the 16:9 TV sets, resulting in reduced vertical resolution. For viewers with 4:3 TV sets the DVD player can create a 16:9 letterboxed image within a 4:3 frame. Multi-channel audio DVD-Video supports PCM, MPEG and Dolby Digital, which can support anything from mono, stereo, Dolby Surround to 5.1 channels. A DVD-Video must use at least one of the formats and can have others as well. Digital Theatre Sound (DTS) and Sony Dynamic Digital Sound (SDDS) are options. Up to eight separate audio streams can be supported, allowing multiple language, audio description, directors 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 so as only to play in a particular region (as defined in the player), a set of regions or be 'code-free'. A region-coded disk can only play on a player that is allowed by the coding. The region numbers are: 1 US, US Territories & Canada 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 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, blurs etc. Picture quality and control also vary widely. DVTR DVTR - Digital Video Tape Recorder. The first DVTR for commercial use was shown in 1986, working to the ITU-R 601 component digital standard and the associated D1 standard for DVTRs. It used 19 mm cassettes recording 34, 78 or (using thinner tape) 94 minutes. Today many DVTR formats are available. D2 and D3, both recording composite signals, are designed mainly to replace C-format (1-inch) analogue machines; Digital Betacam makes use of mild data compression (around 2:1) to record the ITU-R 601 video. D5, like D1, records the full, non-compressed ITU-R 601 signal but on 1¼2-inch tape cassettes. In the professional and news areas video compression is used. Glossary of Terms 23 proxivision media

Multiple generations on DVTRs do not suffer from degradation due to tape noise, moiré, etc. However the tape is subject to wear and tear. The possibility of this producing errors and dropouts necessitates complex error concealment circuitry. In extreme cases multiple passes can introduce cumulative texturing or other artefacts. The safest haven for work that requires heavy multi-generation work is a disk-based system. Dynamic Rounding An intelligent truncation method for digital signals devised by Quantel. There are many instances in digital systems where a number uses more bits than the system normally accommodates. This has to be rectified in a way that will keep as much information as possible and not cause noticeable defects - even after many processes. A common example is image processing which requires that two signals are multiplied, as in digital mixing, producing a 16-bit result from two original 8-bit numbers. This has to be truncated, or rounded, back to 8-bits. Simply dropping the lower bits can result in visible contouring artefacts especially when handling pure, noise-free, computer generated pictures. Dynamic Rounding is a mathematical technique for truncating the word length of pixels - usually to their normal 8 bits. Rather than simply losing the lower bits, it uses the information in those bits to be dropped to control, via a randomizer, the dither of the LSB of the truncated result. This effectively removes the visible artefacts and is non-cumulative on any number of passes. Other attempts at a solution have involved increasing the number of bits, usually to 10, making the LSBs smaller but only masking the problem for a few generations. Dynamic Rounding is licensable from Quantel and is used in a growing number of digital products both from Quantel and other manufacturers. E: EBU European Broadcasting Union. An organization comprising European broadcasters which co- ordinates production and technical interests of European broadcasting. It has within its structure a number of committees which make recommendations to ITU-R. ECC Error Check and Correct. This system appends check data to a data packet in a communications channel or to a data block on a disk, which allows the receiving or reading system both to detect small errors in the data stream (caused by line noise or disk defects) and, provided they are not too long, to correct them. EDL Edit Decision List. A list of the decisions which describe a series of edits - often recorded on a floppy disk. EDLs can be produced during an off-line session and passed to the on-line suite to control the conforming of the final edit. In order to work across a range of equipment there are some widely adopted standards such as CMX 3400 and 3600. Electronic program guides DTV allows broadcasters to transmit electronic program guides. For many, this service is considered essential to keep viewers up to date with the increased number of channels DTV brings. The program guide database allows a receiver to build an on-screen grid of program information and contains control information to facilitate navigation. Glossary of Terms 24 proxivision media

Embedded audio Audio that is carried within an SDI connection - so simplifying cabling and routing. The standard (ANSI/SMPTE 272M-1994) allows up to four groups each of four mono audio channels. Generally VTRs only support Group 1 but other equipment may use more. 48 kHz synchronous audio sampling is pretty well universal in TV but the standard also includes 44.1 and 32 kHz synchronous and asynchronous sampling. Synchronous means that the audio sampling clock is genlocked to the associated video (1920 samples per frame in 625/50, 8008 samples per five frames in 525/60). Up to 24-bit samples are allowed but mostly only up to 20 are currently used. 48 kHz sampling means an average of just over three samples per line, so three samples per channel are sent on most lines and four occasionally - the pattern is not specified in the standard. Four channels are packed into an Ancillary Data Packet and sent once per line (hence a total of 4 x 3 = 12 or 4 x 4 = 16 audio samples per packet per line). Encryption The process of coding data so that a specific code or key is required to restore the original data. In conditional access broadcasts this is used to make transmissions secure from unauthorized reception - as is often found on satellite or cable systems. Entry point A point in a coded bit stream from which a complete picture can be decoded without first having to store data from earlier pictures. In the MPEG-2 frame sequence this can only be at an I-frame - the only frames encoded with no reference to others. Error detection, concealment and correction Both magnetic tape and disks suffer from marginal areas where recording and replay is difficult or even impossible. These errors are detectable and action can be taken to remedy by concealment or correction. The former attempts to hide the problem by making it not so noticeable whereas the latter actually corrects the error so that perfect data is output. Ethernet Ethernet is a form of Local Area Network (LAN) widely used for interconnecting computers and standardized in IEEE 802.3, allowing a wide variety of manufacturers to produce compatible interfaces and extend capabilities - repeaters, bridges, etc. The data transmission rate is 10, 100 or 1,000 Mb/s, but overheads in packaging data and packet separation mean actual throughput is often 5-10 times less than the bit rate. There are many connection methods for Ethernet varying from copper to fibre optic. Currently the most common are: • 10 Base-2 Thinwire Ethernet using relatively low cost 50 ohm coaxial cable and BNC connectors. A maximum length, without repeaters, of 180m and connecting up to 30 devices. • 10 Base-T The standard for 4-wire twisted pair cable using RJ connectors. This gives extremely low cost per node network capabilities. • 100 Base-T A.K.A. Fast Ethernet 100 Mb/s 4-wire twisted pair cable using RJ connectors is now becoming very popular. Similar technology to 10 Base-T but uses Cat. 5 cable. • GigE Fastest Ethernet technology providing high transfer rates, i.e. 1000 Mb/s. Glossary of Terms 25 proxivision media

ETSI The European Telecommunications Standardization Institute. Responsible, amongst other things, for the definition of a compression scheme which, unlike MPEG-2, makes equal demands of the encoder and the decoder. ETSI compression is currently used in a large percentage of satellite contribution links as it only imposes a short processing delay on the signals. ETSI compression A compression technique, based on DCT. Unlike MPEG, which has complex coders and simpler decoders and is designed for broadcast, it is symmetric with the same processing power at the coder and decoder and is designed for applications where there are only a few recipients, such as contribution links and feeds to cable head ends. ETSI compression is intra-frame, simpler than MPEG and imposes less delay in the signal path, typically 120 msec against around a second, enabling interviews to be conducted over satellite links without unwarranted delays. Data rate is 34 Mb/s. EUREKA A European parliamentary body formed to encourage and co-ordinate international collaborative European research projects. EXOR The mathematical operation of EXclusively ORring a number of data bits. For example the EXOR of two bits is 1, only if exactly one of them is 1. The EXOR is widely used in data recovery (see RAID). If the EXOR of a number of blocks of data is stored, when one of those blocks is lost, its contents can be deduced by EXORing the undamaged blocks with the stored EXOR. F: FDDI Fibre Data Distribution Interface. Fettle (color) A suite of color manipulation controls provided on some systems. Operating in Y, Cr, Cb color space the mathematics and control of luminance and color is relatively straightforward. Fibre Channel An integrated set of standards developed by ANSI designed to improve data speeds between workstations, supercomputers, storage devices and displays while providing one standard for networking storage and data transfer. Field sequence A television frame, or picture, comprises two fields. Each successive frame of component 525 and 625 line television repeats a pattern and so can be edited to frame boundaries - like film editing. Composite video, coded as PAL, NTSC or SECAM, carries color information on a subcarrier whose cyclic pattern repeats over a longer period - 4 frames in PAL and 2 frames in NTSC or SECAM - known respectively as the 8 and the 4-field sequence. Glossary of Terms 26 proxivision media

Fire Wall Originally a military term, adopted by the computing industry; a firewall is a piece of hardware or software that functions in a networked environment to prevent certain data transactions. A firewall has the basic task of controlling traffic between different zones of trust. Typical zones of trust include the Internet (a zone with no trust) and an internal network (a zone with high trust). The ultimate goal is to provide controlled connectivity between zones of differing trust levels through the enforcement of a security policy and connectivity model based on the least privilege principle. Proper configuration of firewalls demands skill and understanding by the administrator. It also requires considerable knowledge of network protocols, and computer security. Even small instruction errors can render a firewall obsolete as a security tool. Firewire FireWire (also known as i.Link or IEEE 1394) is a personal computer and digital video serial bus interface standard offering high-speed communications and isochronous real-time data services. FireWire can be considered a successor technology to the obsolescent SCSI Parallel Interface. Firmware Firmware is software that is embedded in a hardware device. Often it is provided in flash ROMs and can be updated by an end user. BIOS are often referred to as Firmware. Fragmentation The scattering of data over a (disk) store caused by successive recording and deletion operations. Generally this will eventually result in the store becoming slow - a situation that is not acceptable for video recording or replay. The slowing is caused by the increased time needed to access randomly distributed data. With such stores de-fragmentation routines arrange the data (by copying from one part of the disk to another) so that it is accessible in the required order for replay. Clearly any change in replay, be it a transmission running order or the revision of an edit, could require further de-fragmentation. True random access stores, able to play frames in any order at video rate, never need de- fragmentation. Glossary of Terms 27 proxivision media

Frequency The number of oscillations of a signal over a given period of time (usually one second). For example it defines subcarrier frequencies in analogue television color coding systems, or clock rate frequencies in digital systems. Some commonly found frequencies in TV: - PAL subcarrier: 4.43 MHz - NTSC subcarrier: 3.58 MHz - ITU-R 601 clock rate: 27 MHz - ITU-R 601 luminance sampling rate: 13.5 MHz - ITU-R 601 chrominance sampling rate: 6.75 MHz (for 4:2:2 sampling) File Transfer Protocol (FTP) FTP or file transfer protocol is a protocol used for exchanging files over the Internet. FTP works in the same way as HTTP for transferring Web pages from a server to a user's browser, and SMTP for transferring electronic mail across the Internet in that FTP uses the Internet's TCP/IP protocols to enable data transfer. FTP is most commonly used to download a file from a server using the Internet or to upload a file to a server (e.g., uploading a Web page file to a server). Full motion video A general term for moving images displayed from a desktop platform. Its quality varies and is undefined. G: Gateway A device connecting between two computer networks. Today many images for use in film or TV are produced on computer systems so an effective connection between these and the dedicated hardware of television is required. Quantel has embedded a gateway as part of its picture networking interface. Generation (loss) The signal degradation caused by successive recordings. Freshly recorded material is first generation, one re-recording, or copy, makes the second, etc. This is of major concern in analogue linear editing but much less so using a digital suite. Non-compressed component DVTRs should provide at least twenty generations before any artefacts become noticeable but the very best multi-generation results are possible with disk-based systems. These can re- recorded millions of times without causing dropouts or errors. Generations are effectively limitless. Besides the limitations of recording, the action of processors such as decoders and coders will make a significant contribution to generation loss. The decode/recode cycle of NTSC and PAL is well known for its limitations but equal caution is needed for digital video compression systems, especially those using MPEG, and the color space conversions that typically occur between computers handling RGB and video equipment using Y, Cr, Cb. See also: Error detection, concatenation, concealment and correction Gigabit Ethernet (see Ethernet) Glossary of Terms 28 proxivision media

Global (control) The top level of control in a multi-channel DVE system. A number of objects (channels) can be controlled at one time, for example to alter their opacity or to move them all together relative to a global axis - one which may be quite separate from the objects themselves. This way the viewing point of all the assembled objects can be changed. For example a cube assembled from six channels could be moved in 3D space as a single action from a global control. GOP (Group of Pictures) When predicting frames from previously encoded frames any errors in the previously encoded frames will degrade the reconstruction of the current frame. This error propagation can be controlled by using a specific frame ordering known as the “Group of Pictures”. A general group of pictures structure is shown below (Reference: Fig 4). Video compression is concerned with coding image sequences at low bit rates. In an image sequence, there are typically high correlations between consecutive frames of the sequence, in addition to the spatial correlations which exist naturally within each frame. Video coders aim to take maximum advantage of interframe temporal correlations (between frames) as well as intraframe spatial correlations (within frames). GPI General Purpose Interface. This is used for cueing equipment - usually by a contact closure. It is simple, frame accurate and therefore can be easily applied over a wide range of equipment. Being electro-mechanical it cannot be expected to be as reliable as pure electronic controls. Grand Alliance (Digital HDTV) The United States grouping, formed in May 1993, to propose 'the best of the best' HDTV systems. The participants were: AT&T, General Instrument Corporation, Massachusetts Institute of Technology, Philips Consumer Electronics, David Sarnoff Research Centre, Thomson Consumer Electronics and Zenith Electronics Corporation. The Grand Alliance has played a big part in arriving at the ATSC digital television standard which uses MPEG-2 video compression and the audio surround-sound compressed with Dolby AC-3. So that a wide variety of source material, including that from computers, can be best accommodated, two line standards are included each operating at 24, 30 and 60 Hz. Glossary of Terms 29 proxivision media

H: Hard disks (fixed disks) Hard or fixed disk drives comprise an assembly of up to 10 rigid platters coated with magnetic oxide, each capable of storing data on both sides. Each recording surface has a write/read head, any one of which may be activated at a given instant. Hard disks give rapid access to vast amounts of data, are highly reliable as they have only two moving parts - the swinging head assembly and the spinning disk. They can be written and read millions of times. Hexadecimal A numbering system; often referred to as 'Hex', that works to base 16 and is particularly useful as a shorthand method for describing binary numbers. Decimal 0-9 are the same as Hex, then 10 is A, 11 is B, up to 15 which is F. Decimal Binary Hex 0-9 0-1001 0-9 10 1010 A 11 1011 B 12 1100 C 13 1101 D 14 1110 E 15 1111 F 16 10000 10 27 11011 1B 100 1100100 64 255 11111111 FF HD D5 A compressed recording system developed by Panasonic which uses compression at about 4:1 to record HD material on standard D5 cassettes. HD D5 supports both the 1080 and the 1035 interlaced line standards at both 60 Hz and 59.94 Hz field rates. Four uncompressed audio channels sampled at 40 kHz, 20 bits per sample, are also supported. HDCam Sometimes called HD Betacam - is a means of recording compressed high-definition video on a tape format which uses the same cassette shell as Digital Betacam, although with a different tape formulation. The technology is aimed specifically at the USA and Japanese 1125/60 markets and supports both 1080 and 1035 active line standards. Quantisation from 10 bits to 8 bits and DCT intra-frame compression are used to reduce the data rate. Four uncompressed audio channels sampled at 48 kHz, 20 bits per sample, are also supported. Glossary of Terms 30 proxivision media

High Definition Television High Definition, sometimes referred to as high def or HD, began in the analogue domain back in the early 1970’s. With the advent of Digital, HD immediately crossed over into the digital domain. Today there are many different HD standards: Common Name # Pixels/Lines Aspect Ratio Frame Rate Scan Type 24p (1080p) 1920 x 1080 16 x 9 23.98 fps* Progressive 25p 1920 x 1080 16 x 9 25 fps Progressive (*) 1080i 1920 x 1080 16 x 9 29.97 fps** Interlaced(**) 720p 1280 x 720 16 x 9 59.94 fps Progressive *23.98p is also referred to as 24 fps **29.97 is also referred to as 30 fps (*) Progressive explained later in this document (**) Interlaced explained later in this document Fundamentally the difference between High Definition and Standard Definition is: frame rate, scan lines, pixel count, size of digital file (much greater) and overall depth of color and clarity. However one of the key reasons that High Definition was initially developed was to create a global standard; for example: analogue television standards vary country by country (i.e. NTSC, PAL and SECAM) and are not compatible with one another. When performing format conversion inevitably picture quality degradation (generation loss) occurs. HiPPI High performance parallel interface (ANSI X3.283-1996). Capable of transfers up to 100 MB/s (800 with the Super HiPPI under development) it is targeted at high performance computing and optimised for applications involving streaming large volumes of data rather than bursty network activity. The parallel connection is limited to short distance and so Serial HiPPI is now available. Huffman coding This compresses data by assigning short codes to frequently-occurring sequences and longer ones to those less frequent. Assignments are held in a Huffman Table. The more likely a sequence is to occur the shorter will be the code that replaces it. It is widely used in video compression systems where it often contributes a 2:1 reduction in data. I: ICMP Internet Control Message Protocol. The part of the Internet Protocol that handles the error and control messages data link layer. The second layer of the Open Systems Interconnect (OSI) communications model. It puts messages together and co-ordinates their flow. IDTV Integrated Digital TV Receiver. Glossary of Terms 31 proxivision media

Illegal colors Colors that force a color system to go outside its normal bounds; usually these are the result of electronically painted images rather than direct camera outputs. For example, removing the luminance from a high intensity blue or adding luminance to a strong yellow in a paint system may well send a subsequent PAL or NTSC coded signal too high or low - producing at least inferior results and maybe causing technical problems. Out of gamut detectors can be used to warn of possible problems. Integrated system Single system which contains more or less enough tools to complete a whole area of operation. In many cases this has only become possible through digital technology and, in turn, it can make it very cost effective. One of an increasing number of examples is Quantel's Editbox which includes most tools required for editing with all operations co-ordinated in one control system. Interlaced Picture Scan When an RGB color gun builds a picture on a television screen it is done so by scanning across the screen from left to right building the color information that creates a picture. With an NTSC system broadcast, images are built top-to-bottom across 525 lines of information (480 active lines) that make up the full TV frame of motion (i.e. picture), with a PAL system 625 lines / 580 active are used. The remaining lines are generally used to delivery information about the broadcast such as closed captioning etc. Two things occur as a consequence of these actions: 1. Vertical Blanking: Caused when the color gun completes one line of color information delivery and resets itself by returning back to the start position on the following line; there is a time gap between the completion of one line and the time it takes for the gun to reset at the beginning of the next line, this lag is referred to as “Vertical Blanking”. Generally vertical blanking occurs so rapidly that even though the human eye sees the transition, the brain does not have sufficient time to register the changes and therefore vertical blanking passes un-noticed by most human beings. 2. Horizontal Blanking: With horizontal blanking, the time delay between the color gun completing frame information - on the last line at the bottom of a screen – and the transition back to the top of the screen to being delivery of the next frame color information is so sufficient that when 30 fps of moving image is delivered there is a noticeable flicker across the screen (those of you reading this who grew up with TV in the 1960’s & 70’s will remember this). To overcome the horizontal blanking found in 30 frames per second delivery, the frame rate has to be increased. Engineers overcame this challenge by dividing each frame of color/motion into two separate parts. Therefore when a frame is scanned for delivery, every other line is scanned and two subsequent frames are the created from one individual frame (frame 1 would capture odd lines, frame 2 captures even lines). When a television receives an interlaced picture it receives 60frames of motion/color information. At the 60 frames per second delivery rate, the two frames are layered back (interlaced) together forming each frame at a higher delivery rate, thus overcoming the flicker a human eye can detect. Interframe Compression Interframe compression is compression applied to a sequence of video frames, rather than a single image. In general, relatively little changes from one video frame to the next. Interframe compression exploits the similarities between successive frames, known as temporal redundancy, to reduce the volume of data required to describe the sequence. Glossary of Terms 32 proxivision media

Example In a sequence of frames the picture captured is a field, with an oak tree in the forefront, and hills in the background. Within picture birds are swooping around. Elements that would stay constant (temporal redundancy) are the hills, the tree, the grass and the sky. Elements that would change (motion compensation) are the plotted movement direction of the birds frame by frame. There are several interframe compression techniques: Sub-sampling Applied to video as an interframe compression technique, by transmitting only some of the frames. Sub-sampled digital video might, for example, contain only every second frame. Either the viewer’s brain or the decoder would be required to interpolate the missing frames at the receiving end. Difference Coding Also known as conditional replenishment is a very simple interframe compression process during which each frame of a sequence is compared with its predecessor and only pixels that have changed are updated. Block Based Difference Coding If the frames are divided into non-overlapping blocks and each block is compared with its counterpart in the previous frame, then only blocks that change significantly need be updated. Block Based Motion Compensation Block based motion compensation, like other interframe compression techniques, produces an approximation of a frame by reusing data contained in the frame’s predecessor. Intraframe Explained I Fames are essentially the main anchor frames. No motion estimation is performed to generate these frames. They are transform-coded directly to file and ensure the highest possible quality in digital reconstruction. This is because all following frames are predicted from the I Frame. And any error in the I Frame will propagate through the rest of the group. In the MPEG-2 sequence only I-frames can be edited as they are the only independent frames. Interpolation (spatial) When re-positioning or re-sizing a digital image inevitably more, less or different pixels are required from those in the original image. Simply replicating or removing pixels causes unwanted artefacts. For far better results the new pixels have to be interpolated - calculated by making suitably weighted averages of adjacent pixels - to produce a more transparent result. The quality of the results will depend on the techniques used and the number of pixels (points - hence 16- point interpolation), or area of original picture, used to calculate the result. Interpolation (temporal) Interpolation between the same point in space on successive frames. It can be used to provide motion smoothing and is extensively used in standards converters to reduce the judder caused by the 50/60 Hz field rate difference. The technique can also be adapted to create frame averaging for special effects. Glossary of Terms 33 proxivision media

Internet The Internet, or simply the Net, is the worldwide system of interconnected computer networks, and servers that allows associated stored content to be accessible by any user surfing the net. This information is transmitted by packet switching using a standardized Internet Protocol (IP); the first TCP/IP was operational in 1984. It is made up of billions of smaller commercial, academic, domestic and government networks. It carries various information and services, such as electronic mail, online chat, instant messaging, gaming, VOIP, and interlinks web pages, blogs and other documents across the World Wide Web. Intranet An intranet is a private network that uses the internet protocols to securely share information around an organization. A good example of this solution, but not limited to, is the internal company website your organization has. ISO International Standards Organisation; an international organization that specifies international standards, including those for networking protocols, compression systems, disks, etc. ISO layer A model containing seven conceptual layers, each providing a set of services that are used in network operations. ITC Independent Television Commission. It is responsible as a regulator, both legally and technically, for all independent programming in the United Kingdom, be it cable, satellite or terrestrial. ITU-R 601 Full title: ITU-R Rec. BT. 601-5. This standard defines the encoding parameters of digital television for studios. It is the international standard for digitising component television video in both 525 and 625 line systems and is derived from the SMPTE RP125. ITU-R 601 deals with both color difference (Y, R-Y, B-Y) and RGB video, and defines sampling systems, RGB/Y, R-Y, B-Y matrix values and filter characteristics. It does not actually define the electro-mechanical interface. ITU-R 601 is normally taken to refer to color difference component digital video (rather than RGB), for which it defines 4:2:2 sampling at 13.5 MHz with 720 luminance samples per active line and 8 or 10-bit digitising. Some headroom is allowed with black at level 16 (not 0) and white at level 235 (not 255) - to minimize clipping of noise and overshoots. Using 8-bit digitising approximately 16 million unique colors are possible: 28 each for Y (luminance), Cr and Cb (the digitized color difference signals) = 224 = 16,777,216 possible combinations. The sampling frequency of 13.5 MHz was chosen to provide a politically acceptable common sampling standard between 525/60 and 625/50 systems, being a multiple of 2.25 MHz, the lowest common frequency to provide a static sampling pattern for both. ITU-R 656 Interfaces for digital component video signals in 525-line and 625-line television systems. The international standard for interconnecting digital television equipment operating to the 4:2:2 standard defined in ITU-R 601. It defines blanking, embedded sync words, the video multiplexing formats used by both the parallel (now rarely used) and serial interfaces, the electrical characteristics of the interface and the mechanical details of the connectors. Glossary of Terms 34 proxivision media

J: Java A general purpose programming language developed by Sun Microsystems and best known for its widespread use on the World Wide Web. Unlike other software, programs written in Java can run on any platform type, so long as they contain a Java Virtual Machine. JPEG Joint Photographic Experts Group, ISO/ITU-T. JPEG is a standard for the data compression of still pictures (intra-frame). In particular its work has been involved with pictures coded to the ITU- R 601 standard. It offers data compression of between two and 100 times and three levels of processing are defined: the baseline, extended and lossless encoding. JPEG baseline compression coding, which is overwhelmingly the most common in both the broadcast and computer environments, starts with applying DCT to 8 x 8 pixel blocks of the picture, transforming them into frequency and amplitude data. This itself may not reduce data but then the generally less visible high frequencies can be divided by a high factor (reducing many to zero), and the more visible low frequencies by a lower factor. The factor can be set according to data size or picture quality requirements - effectively adjusting the compression ratio. The final stage is Huffman coding which is lossless but can further reduce data by about 2:1. Baseline JPEG coding is very similar to the I-frames of MPEG, the main difference being they use slightly different Huffman tables. K: Keycode A machine-readable bar-code printed along the edge of camera negative stock outside the perforations. It gives key numbers, film type, film stock manufacturer code, and offset from zero- frame reference mark (in perforations). It has applications in telecine for accurate film-to-tape transfer and in editing for conforming neg. cuts to EDLs. Keyframe A set of parameters defining a point in a transition, eg of a DVE effect. For example a keyframe may define a picture size, position and rotation. Any digital effect must have a minimum of two keyframes, start and finish, although more complex moves will use more - maybe as many as 100. Increasingly, more parameters are becoming 'keyframeable', ie they can be programmed to transition between two, or more, states. Keying The process of selectively overlaying an area of one picture (or clip) onto another. If the switch between the overlaid and background pictures is simply a hard switch this can lead to jagged edges of the overlaid, or keyed, pictures. They are usually subjected to further processing to give a cleaner, more convincing, result. The whole technology of deriving a key signal has greatly expanded through the use of digital technology, so that many operations may be used together, eg softening the key, color correcting key spill areas, and more. Glossary of Terms 35 proxivision media

L: Local Area Network (LAN) A local area network LAN is a computer network covering a small local area, like a home, office, or small group of buildings such as a college. Current LANs are most likely to be based on switched Ethernet or Wi-Fi technology running at from 10 to 1000Mb/s (megabits per second). The defining characteristics of LANs in contrast to WANs are: (a) much higher data rates, (b) smaller geographic range and (c) they do not involve leased telecommunication lines. Latency The delay between requesting and accessing data. For disk drives it refers to delay due to disk rotation. The faster a disk spins the quicker it will be at the position where the required data can start to be read. As disk diameters have decreased so rotational (spindle) speeds have tended to increase but there is still much variation Layer(ing) A collection, or 'pack' of clip layers can be assembled to form a composite layered clip. Layers may be background video or foreground video with its associated matte run. The ability to compose many layers simultaneously means the result to be seen as it is composed and adjustments made as necessary. Linear (editing) The process of editing footage that can only be accessed or played in the sequence recorded. Tape is linear in that it has to be spooled for access to any material and can only play pictures in the order they are recorded. Linear (keying) Selective overlay of one video signal over another, the ratio of foreground to background at any point being determined on a linear scale by the level of the key (control) signal. This form of keying provides the best possible edges and anti-aliasing. It is essential for the realistic keying of semi-transparent effects such as transparent shadows, through windows and partial reflections. Load Balancing In computing, load balancing is a technique used to spread work between many processes, computers, disks or other resources. Generally this is required when large volumes of users request webpages or digital media simultaneously. Load balancing is of concern paramount when considering solutions that will scale dramatically over time. Lossy Data Compression: A lossy data compression method is one where compressing a file and then decompressing it retrieves a file that may well be different to the original, but is \"close enough\" to be useful in some way. This type of compression is used frequently on the Internet and especially in streaming media and telephony applications. These methods are typically referred to as codecs in this context. Contrast with lossless data compression. Glossary of Terms 36 proxivision media

Fig. 4 Example of Lossy Compression Original Image (12KB size) Compressed (85% less Highly Compressed information, 1.8KB) (96% less information, 0.56KB) The above images show the use of lossy compression to reduce the file size of the image. The image is an excerpt of the image of Lena, a de facto industry-standard test image. The first picture is 12,249 bytes. • The second picture has been compressed (JPEG quality 30) and is 85% smaller, at • 1,869 bytes. Notice the loss of detail in the brim of the hat. The third picture has been highly compressed (JPEG quality 5) and is 96% smaller, at • 559 bytes. The compression artifacts are much more noticeable. Even though the third image has high distortion, the face is still recognizable. Good lossy compression algorithms are able to throw away \"less important\" information and still retain the \"essential\" information. Lossless data compression: Is a class of data compression algorithms that allows the original data to be reconstructed exactly from the compressed data - Contrast with lossy data compression. Lossless data compression is used in software compression tools such as the highly popular ZIP file format, used by PKZIP, WinZip and Mac OS 10.3, and the Unix programs bzip2, gzip and compress. Other popular formats include Stuffit, RAR and 7z. Lossless compression is used when it is important that the original and the decompressed data be identical, or when no assumption can be made on whether certain deviation is uncritical. Typical examples are executable programs and source code. Some image file formats, notably PNG, use only lossless compression, while others like TIFF and MNG may use either lossless or lossy methods. GIF uses a technically lossless compression method, but most GIF implementations are incapable of representing full color, so they quantize the image (often with dithering) to 256 or fewer colors before encoding as GIF. Color quantization is a lossy process, but reconstructing the color image and then re-quantizing it produces no additional loss. (Some rare GIF implementations make multiple passes over an image, adding 255 new colors on each pass.) Lossy vs. Lossless Compression The advantage of lossy methods over lossless methods is that in some cases a lossy method can produce a much smaller compressed file than any known lossless method, while still meeting the requirements of the application. Glossary of Terms 37 proxivision media

Lossy methods are most often used for compressing sound or images. In these cases, the retrieved file can be quite different to the original at the bit level while being indistinguishable to the human ear or eye for most practical purposes. Many methods focus on the idiosyncrasies of the human anatomy, taking into account, for example, that the human eye can see only certain frequencies of light. The psychoacoustic model describes how sound can be highly compressed without degrading the perceived quality of the sound. Flaws caused by lossy compression that are noticeable to the human eye or ear are known as compression artifacts. LTC Longitudinal timecode; timecode recorded on linear track on tape and read by a static head. This can be easily read when the tape is moving forwards or backwards but not at freeze frame, when VITC, timecode recorded with the picture material, can be used. Luminance A component, the black and white or brightness element, of an image. It is written as Y, so the Y in Y (B-Y) (R-Y),YUV, YIQ, Y, Cr, Cb is the luminance information of the signal. In a color TV system the luminance signal is usually derived from the RGB signals, originating from a camera or telecine, by a matrix or summation of approximately: Y = 0.3R + 0.6G + 0.1B M: Metropolitan Area Network (MAN) Metropolitan Area Networks or MAN’s are large computer networks usually spanning a campus or a city. They typically use wireless infrastructure or optical fiber connections to link their sites. Megahertz (MHz) A frequency of millions of cycles (or samples) per second. Metadata – in Greater Detail Metadata (Greek: meta-+data \"information\"), literally \"data about data\", is information that describes another set of data. A common example is a library catalog card, which contains data about the contents and location of a book: It is data about the data in the book referred to by the card. Other common contents of metadata include the source or author of the described dataset, how it be accessed, and its limitations. The content combined with its metadata is often called a content package. Metadata has become important on the World Wide Web because of the need to find useful information from the mass of information available. Manually-created metadata adds value because it ensures consistency. If one webpage about a topic contains a word or phrase, then all webpages about that topic should contain that same word. It also ensures variety, so that if one topic has two names, each of these names will be used. For example, an article about Sports Utility Vehicles would also be given the metadata keywords ‘4 wheel drives’, ‘4WDs’ and ‘four wheel drives’, as this is how they are known in some countries. For examples of metadata for an audio CD, look at the MusicBrainz project, or AMG's All Music Guide. Similarly, MP3 files have metadata tags in a format called ID3. Glossary of Terms 38 proxivision media

Metadata is more properly called ontology or schema when it is structured into a hierarchical arrangements. Both terms describe “what exists” for some purpose or to enable some action. For instance, the arrangement of subject headings in a library catalog serves as not only a guide to finding books on a particular subject in the stacks, but also as a guide to what subjects “exist” in the library’s own ontology and how the more specialized topics are related to or derived from the more general subject headings. MXF Descriptive Metadata is based on two important SMPTE standards RP-210 and DMS-1 (S380M) that have been defined as part of MXF. RP-210 is often referred to as the “SMPTE Metadata Dictionary” which defines over 1500 tags of metadata establishing a common vocabulary between manufacturers. DMS-1 adds semantics or “contextual meaning” to RP-210 labels. DMS-1 metadata covers an extensive list of descriptors that include Titles, Cue Words, Award, Captions Description, Annotation, Scripting, Classification, Rights, Persons, Organizations, Locations, Addresses, Contact Lists, Communications, and Contracts. DMS-1 is fully standardized and completely interoperable between MXF systems. It is similar to the metadata that can be found in multimedia files such as MP3, ASF and Quicktime but covers a more extensive range of topics that are relevant to the professional media market. As with those multimedia file formats, the metadata in the file is standardized and coupled with the media so it is always carried with the file ensuring true interoperability and longevity of the information. Moore's Law A prediction for the rate of development of modern electronics. This has been expressed in a number of ways but in general states that the density of information storable in silicon roughly doubles every year. Or, the performance of silicon will double every eighteen months, with proportional decreases in cost. For more than two decades this prediction has held true. Moore's law initially talked about silicon but it could be applied to disk drives: the capacity of disk drives doubles every two years. That has been true since 1980, and will continue well beyond 2000. Motion-Compensated Predictive Coding Motion-compensated predictive coding (MCPC) is the technique that has been found to be most successful for exploiting interframe correlations. Glossary of Terms 39 proxivision media

The transform, quantize, and entropy encode functions are basically the same as those employed for still image coding. The first frame in a sequence is coded in the normal way for a still image by switching the prediction frame to zero. For subsequent frames, the input to the transform stage is the difference between the input frame and the prediction frame, based on the previous decoded frame. This difference frame is usually known as the prediction error frame. The purpose of employing predictions is to reduce the energy of the prediction error frames so that they have lower entropy after transformation and can therefore be coded with a lower bit rate. If there is motion in the sequence, the prediction error energy may be significantly reduced by motion compensation. This allows regions in the prediction frame to be generated from shifted regions from the previous decoded frame. Each shift is defined by a motion vector which is transmitted to the decoder in addition to the coded transform coefficients. MPEG Moving Picture Experts Group, ISO/CCITT. MPEG is involved in defining standards for the data compression of moving pictures. Its work follows on from that of JPEG to add inter-frame compression, the extra compression potentially available through similarities between successive frames of moving pictures. MPEG-2 Transmission The MPEG-2 standards define how to format the various component parts of a multimedia program (which may consist of: MPEG-2 compressed video, compressed audio, control data and/or user data). It also defines how these components are combined into a single synchronous transmission bit stream. The process of combining the steams is known as multiplexing. The multiplexed stream may be transmitted over a variety of links: 1. Radio Frequency Links (UHF/VHF) 2. Digital Broadcast Satellite Links 3. Cable TV Networks 4. Standard Terrestrial Communication Links (PDH, SDH) 5. Microwave Line of Sight (LoS) Links (wireless) 6. Digital Subscriber Links 7. Packet / Cell Links (ATM, IP, IPv6, Ethernet, GigE) MPEG-2 Elementary Stream The most basic component of MPEG-2; a program (perhaps most easily thought of as a television program, or a Digital Versatile Disk (DVD) track) contains a combination of elementary streams (i.e. one for video, one or more for audio, control data, subtitles, etc). MPEG Transport Stream Each PES packet is broken into fixed-sized transport packets forming a general purpose way of combining one or more streams, possibly with independent time bases. This is suited for transmission in which there may be potential packet loss or corruption by noise, or / and where there is a need to send more than one program at a time. MPEG Program Stream A group of tightly coupled PES packets referenced to the same time base. Such streams are suited for transmission in a relatively error-free environment and enable easy software processing of the received data. This form of multiplexing is used for video playback and for some network applications. Glossary of Terms 40 proxivision media

MTBF Mean Time Between Failure; a statistical assessment of the average time taken for a unit to fail - a measure of predicted reliability. The MTBF of a piece of equipment is dependent on the reliability of each of its components. Generally the more components the lower the MTBF, so packing more into one integrated circuit can reduce the component count and increase the reliability. Modern digital components are highly reliable. Multiplex A term for the group of compressed video channels multiplexed into single transmission feed. The term \"Bouquet\" has also been used in this context. Multi Layer Switch (Layer 3 Routing) Multi layer switches connect network segments on different subnets, by routing between them. They can also create \"broadcast firewalls\" between ports or groups of ports (and, thus, between any devices you attach to those ports). These groups are called \"bridged groups\" or \"virtual LANs\", and each behaves like a bridged network. MXF MXF (Material eXchange Format) is a \"container\" or \"wrapper\" format that supports a number of different streams of coded \"essence\", encoded with any of a variety of codecs, together with a metadata wrapper which describes the material contained within the MXF file. MXF has been designed to address a number of problems with non-professional formats. MXF has full timecode and metadata support, and is intended as a platform-agnostic stable standard improving file-based interoperability between servers, workstations and other content creation devices - for future professional video and audio applications. N: Networked Attached Storage (NAS) Network-attached storage (NAS) systems are generally computing-storage devices that can be accessed over a computer network (usually TCP/IP), rather than directly being connected to the computer (via a computer bus such as SCSI). This enables multiple computers to share the same storage space at once, which minimizes overhead by centrally managing hard disks. NAS systems usually contain one or more hard disks, often arranged into logical, redundant storage containers or RAID arrays. Network layer In TCP/IP, the network layer is responsible for accepting IP (Internet Protocol) datagrams and transmitting them over a specific network. NFS Network File System. Developed by Sun Microsystems NFS allows sets of computers to access each other's files as if they were locally stored. NFS has been implemented on many platforms and is considered an industry standard. Nibble 8 binary bits = 1 Byte 4 binary bits = 1 Nibble Glossary of Terms 41 proxivision media

Noise (Random) Irregular level fluctuations of a low order of magnitude; all analogue video signals contain random noise. Ideally for digital sampling, the noise level should not occupy more than one LSB of the digital dynamic range. Pure digitally generated signals however do not contain any noise - a fact that can be a problem under certain conditions. Generally in ITU-R 601 systems fine noise is invisible; coarse or large area noise may be perceptible under controlled viewing conditions. With digital compression noise has a new importance. As it has to discriminate between noise and wanted signal, noise is the enemy of digital compression. Non-additive mix A mix of two pictures which is controlled by their luminance levels relative to each other, as well as a set mix value K (between 0 and 1): eg the position of a switcher lever arm. A and B sources are scaled by factors K and 1-K but the output signal is switched to that which has the greatest instantaneous product of the scaling and the luminance values. The output of any pixel is either signal A or B but not a mix of each. So if K = 0.5, where picture A is brighter than B then only A will be seen. Thus two clips of single subjects shot against a black background can be placed in one picture. The term has also come to encompass some of the more exotic types of picture mixing available today: for example to describe a mix that could add smoke to a foreground picture - perhaps better termed an additive mix. Non-drop-frame timecode Timecode that does not use drop-frame and always identifies 30 frames per second. This way the timecode running time will not exactly match normal time. The mismatch amounts to 1:1000, an 18-frame overrun every 10 minutes. This applies to 525/60 systems only as 625/50 systems have an exact number of frames per second. Non-linear (editing) Non-linear means not linear - that the recording medium is not tape and editing can be performed in a non linear sequence - not necessarily the sequence of the program. It describes editing with quick access to source clips and record space - usually using computer disks to store footage. This removes the spooling and pre-rolls of VTR operations so greatly speeding work, yet greater speed and flexibility are possible with real-time random access to any frame (true random access). NTSC The United States National Television Systems Committee NTSC (Television Standard) The color television system used in the USA, Canada, Mexico and Japan where NTSC M is the broadcast standard (M defining the 525/60 line and field format - often the standard is just referred to as NTSC). It was defined by the NTSC. The bandwidth of the NTSC system is 4.2 MHz for the luminance signal and 1.3 and 0.4 MHz for the ‘I’ and ‘Q’ color channels. Glossary of Terms 42 proxivision media

Nyquist (frequency) The minimum frequency which will faithfully sample an analogue signal. This is always twice the maximum frequency of the signal to be sampled. Sampling wideband signal at frequency f In practice significantly higher sampling frequencies are used in order to stay well above the Nyquist frequency and so avoid the chance of producing aliens (unwanted artifacts) and the severe attenuation, according to a Sin x/x characteristic, that exists around the Nyquist point. For example in ITU-R 601 the maximum luminance frequency is 5.5 MHz and its sampling frequency is 13.5 MHz. O: Off-line (editing) A decision-making process using low-cost equipment usually to produce an EDL or a rough cut which can then be conformed or referred to in a high quality on-line suite - so reducing decision- making time in the more expensive on-line environment. While most off-line suites enable shot selection and the defining of transitions such as cuts and dissolves, very few allow settings for the DVEs, color correctors, keyers and layering that are increasingly a part of the on-line editing process. On-line (editing) Production of the complete, final edit performed at full program quality - the buck stops here! Being higher quality than off-line, time costs more but the difference is reducing. Preparation in an off-line suite will help save time and money in the on-line. To produce the finished edit on-line has to include a wide range of tools, offer flexibility to try ideas and accommodate late changes, and to work fast to maintain the creative flow and to handle pressured situations. Glossary of Terms 43 proxivision media

Operating system The base program that manages a computer and gives control of the functions designed for general purpose usage - not for specific applications. Common Operating Systems are: • Windows • Unix • OSX (Apple) • Red Hat OSI layers: There are seven Open System Interconnection layers defined by the International Standards Organisation for networking framework. Fortunately, users don’t need to know anything about them, except that the lower the layer number, the closer you are to the hardware. In network communication, control passes from the higher levels to the lower ones at one end, over the network connection to the next network station, and back up the levels again. All seven layers put together make up the entire network system from an application/software to the wires, and how each layer actually works in the real world is defined by a plethora of other protocols. For example, Ethernet and Token Ring are two different ways of providing the services defined by OSI layers 1 and 2, the Physical and Data Link layers. OSI Name Function layer Communication between programs. This is the layer that 7 Application Layer user programs talk to. Data representation conversions; this layer translates data, 6 Presentation Layer between what the network requires and what the computers at each end expect. Establishes and maintains communications channels, so 5 Session Layer program on different computers can establish a link. Often combined with the Transport Layer. Responsible for end-to-end data transmission integrity. 4 Transport Layer Makes sure that the data actually gets there, with no errors, in the right order, regardless of transmission problems. Routes data from one network node to another. This layer translates \"logical\" device names and addresses into their 3 Network Layer network hardware equivalents, and does routing, if necessary, for devices that are more than one network link away. Takes care of moving data from one network node to 2 Data Link Layer another, not more than one link away. Translates the bits generated by all the other layers into 1 Physical Layer signals to send through the network, and translates them back into bits at the other end. Glossary of Terms 44 proxivision media

Optical disks Disks using optical techniques for recording and replay of material, offering large storage capacities within a very small area. P: Pack A set of clips, mattes and settings for DVE, color corrector, keyer, etc. that are used together to make a video layer in a composited picture. Packet Switching Packet switching, as used by the TCP/IP protocol on which the Internet is built, can be compared with simple \"circuit switching\", as used by the phone network, where a dedicated link is established from point to point whenever one device needs to communicate with another. Circuit switching is faster, works with much lower-tech equipment and guarantees that data will arrive in the same order it was sent, important for live audio and video. Packet switching is more efficient and can tolerate slower and much less reliable connections. PAL Phase Alternating Line. The color coding system for television widely used in Europe and throughout the world, almost always with the 625/50 line/field system. It was derived from the NTSC system but by reversing the phase of the reference color burst on alternate lines (Phase Alternating Line) is able to correct for hue shifts caused by phase errors in the transmission path. Bandwidth for the PAL-I system is typically 5.5 MHz luminance, and 1.3 MHz for each of the color difference signals, U and V. PAL-M A version of the PAL standard, but using a 525 line 60-field structure. Used only in parts of South America (eg Brazil). Parallel processing Using several processors simultaneously with the aim of increasing speed over single processor performance. Parsing In computer science, parsing is the process of analyzing a continuous stream of input (read from a file or a keyboard, for example) in order to determine its grammatical structure with respect to a given formal grammar. A parser is a computer program that carries out this task. The name is by analogy with the usage in grammar and linguistics. The term parseable is generally applied to text or data which can be parsed. Parsing transforms input text into a data structure, usually a tree, which is suitable for later processing and which captures the implied hierarchy of the input. Generally, parsers operate in two stages, first identifying the meaningful tokens in the input, and then building a parse tree from those tokens. Pixel (or Pel) A shortened version of 'Picture cell' or 'Picture element'. The name given to one sample of picture information. Pixel can refer to an individual sample of R, G, B luminance or chrominance, or sometimes to a collection of such samples if they are co-sited and together produce one picture element. Glossary of Terms 45 proxivision media

PLD Programmable Logic Device. Various types of PLD include: - PROM - Programmable Read Only Memory - PLA - Programmable Logic Array - PAL - Programmable Array Logic, registered trade-mark of Monolithic Memories Inc. - FPGA - Field Programmable Gate Array Integrated circuits which can be programmed to perform various logic functions. They generally comprise an array of AND and OR gates, and often registers. The interconnections between these logic elements can be configured, or programmed, for the desired functions. The interconnections may be controlled in several ways: by fuses or 'anti-fuses' which permanently make or break links or by transistors combined with a memory element. In the latter case the memory may be erasable electrically or by exposure to ultra-violet light, allowing the devices to be re-programmed, or it may be volatile in which case the device must be reconfigured every time it is powered up. Predictive Picture P frames are predicted using MCP (Motion Compensation Prediction) from the preceding I or P frames. P frames contain descriptions of how the pixels have changed from one frame to the next frame in a particular sequence. These descriptions of data i.e. pixels, distance, and direction of movement, are referred to as “Motion Vectors”. If there is a change in luminance and color (YCbCr), that data change/difference is also captured and applied to the motion vector. Progressive (scan) Method of scanning lines down a screen - as is commonly used with computers - where all the lines of a picture are displayed in one vertical scan. A high picture rate is required to give good movement portrayal and to avoid a flickery display. For television applications this implies a high bandwidth or data rate. The vertical definition is equal to its number of lines and does not show the dither of detail associated with interlaced scans. Unlike the problems found in Television, a computer is able to refresh its screen a rapid 72 times per second. Because this rate is faster than persistence of vision, the problem of picture flicker is no longer a variable, and the need to interlaced pictures is removed. Thus the image is scanned from top-to-bottom and a full frame of motion/color is delivered onto the screen. Additionally because the frame is no longer divided a complete frame of motion/color video is delivered creating a fifty percent increase in overall clarity. Glossary of Terms 46 proxivision media

Positioning time The time taken for the read/write heads of a disk drive to be positioned over a required track. Average positioning time is the time to reach any track from the centre track. Maximum positioning time is the time to reach any track from any track. A high performance modern disk will offer around 7 ms for the former and 14 ms for the latter. Q: Quantising The process of sampling an analogue waveform to provide packets of digital information to represent the original analogue signal R: RAID Redundant Array of Independent Disks. A grouping of standard disk drives together with a RAID controller to create storage that acts as one disk to provide performance beyond that available from individual drives. Primarily designed for operation with computers, RAIDs can offer very high capacities, fast data transfer rates and much increased security of data. The latter is achieved through disk redundancy so that disk errors or failures can be detected and corrected. A series of RAID configurations is defined by levels and, being designed by computer geeks, they start counting from zero. Different levels are suited to different applications: Level 0: No redundancy - benefits only of speed and capacity - generated by combining a • number of disks. Level 1: Complete mirror system - two sets of disks both reading and writing the same • data. This has the benefits of level 0 plus the security of full redundancy - but at twice the cost. Some performance advantage can be gained in read because only one copy need be read, so two reads can be occurring simultaneously. Level 2: An array of nine disks. Each byte is recorded with one bit on each of eight disks • and a parity bit recorded to the ninth. This level is rarely, if ever, used. Level 3: An array of n+1 disks recording 512 byte sectors on each of the n disks to create • n x 512 'super sectors' + 1 x 512 parity sector on the additional disk which is used to check the data. The minimum unit of transfer is a whole superblock. This is most suitable for systems in which large amounts of sequential data are transferred - such as for audio and video. For these it is the most efficient RAID level since it is never necessary to read/modify/write the parity block. It is less suitable for database types of access in which small amounts of data need to be transferred at random. Level 4: As level 3 but individual blocks can be transferred. When data is written it is • necessary to read the old data and parity blocks before writing the new data as well as the updated parity block, which reduces performance. Level 5: As level 4, but the role of the parity disk is rotated for each block. In level 4 the • parity disk receives excessive load for writes and no load for reads. In level 5 the load is balanced across the disks. Glossary of Terms 47 proxivision media

Soft RAID A RAID system implemented by low level software in the host system instead of a dedicated RAID controller. While saving on hardware, operation consumes some of the host's power. Resolution A measure of the finest detail that can be seen, or resolved, in a reproduced image. Whilst it is influenced by the number of pixels in the display (e.g. high definition approximately 2000 x 1000, broadcast SDTV 720 x 576 [PAL] or 720 x 487 [NTSC]) note that the pixel numbers do not define the resolution but merely the resolution of that part of the equipment. The quality of lenses, display tubes, film processes, edit systems and film scanners, etc. in fact any element in the program stream (from scene to screen), must be taken into account. Resolution independent A term used to describe the notion of equipment that can operate at more than one resolution. Most dedicated television equipment is designed to operate at a single resolution although some modern equipment, especially that using the ITU-R 601 standard, can switch between the specific formats and aspect ratios of 525/60 and 625/50. By their nature computers can handle files of almost any size so, when used to handle images, they can be termed \"resolution independent\". However as larger images require more processing, more storage and more bandwidth, so for a given platform the speed of operation will slow as the resolution increases. RGB The abbreviation for the Red, Green and Blue signals, the primary colors of television. Cameras and telecines have red, blue and green receptors; the TV screen has red, green and blue phosphors illuminated by red, green and blue guns. Much of the picture monitoring in a production centre is in RGB. RGB is digitized with 4:4:4 sampling which occupies 50% more data than 4:2:2 (Random Trivia: your guide throughout this documents father was a member of the engineering team that designed the RGB color gun used in television sets) RIP Raster Image Process; the method of converting vector data (for example fonts) into raster image form - making it suitable for use as, or in, a television picture. Vector data is size independent and so has to be RIPped to a given size. RIPping to produce high quality results requires significant processing - especially if interactive operation is required, for example to fit the result into a background. Rotoscoping The practice of using frames of live footage as reference for painting animated sequences. While the painting will always be down to the skill of the artist, modern graphics equipment integrated with a video disk store makes rotoscoping, or any graphical treatment of video frames, quick and easy. This has led to many new designs and looks appearing on television as well as more mundane practices such as image repair. Router A router is a device that connects networks together, like a bridge, but is a great deal smarter. Routers operate at OSI layer 3, which means they understand both logical and physical addresses when moving data around, unlike bridges, which work at layer 2 and only understand physical addresses. Routers analyze incoming packets and modify them, if necessary, so they’re redirected to another router or to their initially intended destination. This allows routers to send packets from one kind of network across another kind of network on their way to a destination network which can be of yet another kind, via more routers if necessary. As long as the routers know what computers live where, a router can figure out the necessary route intelligently. Glossary of Terms 48 proxivision media

RP 125 SMPTE Recommended Practice 125 - bit-parallel digital interface for component video signals. One of the forerunners of ITU-R 656. RS 232 A standard for serial data communications defined by EIA standard RS-232 and is designed for short distances only - up to 10 meters. It uses single-ended signaling with a conductor per channel plus a common ground, which is relatively cheap, easy to arrange but susceptible to interference - hence the distance limitation. RS 422 Not to be confused with 4:2:2 sampling, this is a standard for serial data communications defined by EIA standard RS-422. It uses current-loop, balanced signaling with a twisted pair of conductors per channel, two pairs for bi-directional operation. It is more costly than RS232 but has a high level of immunity to interference and can operate over reasonably long distances - up to 300m/1000 ft. RS 422 is widely used for control links around production and post areas for a range of equipment - VTRs, mixers, etc. and in all links between Quantel control stations and the main equipment. RSN Real Soon Now! A phrase coined by Jerry Pournelle to satirize the tendency in the computer industry of discussing (and even offering for sale) things that are not actually available yet. Run-Length Coding A system for compressing data. The principle is to store a pixel value along with a message detailing the number of adjacent pixels with that same value. This gives a very efficient way of storing large areas of flat color and text but is not so efficient with pictures from a camera, where the random nature of the information, including noise, may actually mean that more data is produced than was needed for the original picture. S: Sampling Process applied to convert an analogue signal into a series of digital values. Alternative term for quantizing. Sampling standard A standard for sampling analogue waveforms to convert them into digital data. The official sampling standard for television is ITU-R 601. Server A computer software application that carries out some task (i.e. provides a service) on behalf of yet another piece of software called a client. In the case of the Web: An example of a server is the Apache web server, and an example of a client is the Internet Explorer web browser or the Mozilla web browser. Other server (and client) software exists for other services such as e-mail, printing, remote login, and even displaying graphical output. This is usually divided into file serving, allowing users to store and access files on a common computer; and application serving, where the software runs a computer program to carry out some task for the users. This is the original meaning of the term. Web, mail, and database servers are what most people access when using the Internet. Glossary of Terms 49 proxivision media

Server (video) A storage system that provides audio and video storage for a network of clients. While there are some analogue systems based on optical disks, those used in professional and broadcast applications are based on digital disk storage. Aside from those used for video on demand (VOD), video servers are applied in three areas of television operation: transmission, post production and news. Compared to general purpose file servers, video servers must handle far more data, files are larger and must be continuously delivered. Storage Area Network (SAN) In computing, a storage area network (SAN) is a network designed to attach computer storage devices such as disk array controllers and tape libraries to servers. As of 2005, SANs have become common place in enterprise storage Scaling Analogue video signals have to be scaled prior to digitising in an ADC so that the full amplitude of the signal makes full use of the available levels in the digital system. The ITU-R 601 digital coding standard specifies black to be set at level 16 and white at 235. Computer systems tend to operate with a different scaling: black set to level 0 and white at 255, but for color they usually use RGB from 0-255. Clearly, going between computers and TV requires processing to change color space and scaling. SCH Sub-carrier to horizontal sync timing relationship. Chrominance information in PAL and NTSC is borne by a color sub-carrier whose frequency is mathematically related to the line and field scanning rates. PAL and NTSC expect this relationship to remain fixed otherwise the picture may hop, jump or be subjected to further processing (if available) which may change its quality. Scrambling Similar to encryption, in which data or transmissions are 'scrambled' so they can only be retrieved by authorized users. Scrub (audio) Replay of audio tracks at a speed and pitch corresponding to jog speed - as heard with analogue audio tape 'scrubbing' past an audio head. This feature, which is natural for analogue, fixed-head recorders, may be provided on a digital system recording on disks to help set up cues. SDDI Serial Digital Data Interface - designed for serial digital information to be carried over a standard SDI (video) path. Although the information contained in the SDDI stream will often include video, it can also carry non-video data. SDTI Serial Digital Transport Interface. Based on SDI, this does not define the format of the signals carried but brings the possibility to create a number of packetized data formats for broadcast use. Currently these are expected to include a Sony native format, an MPEG-2 transport stream format, and MPEG-2 audio/video/metadata elementary stream format, a DVCAM format (QSDI), and a DVCPRO format (CSDI). Doubtless others will follow. Glossary of Terms 50 proxivision media

SDTV Standard Definition Television. A digital television system in which the quality is approximately equivalent to that of NTSC or PAL. Pictures might be derived from an ITU-R 601 source which has been subjected to bit-rate compression. Server (video) A storage system that provides audio and video storage for a network of clients. While there are some analogue systems based on optical disks, those used in professional and broadcast applications are based on digital disk storage. Aside from those used for video on demand (VOD), video servers are applied in three areas of television operation: transmission, post production and news. Compared to general purpose file servers, video servers must handle far more data, files are larger and must be continuously delivered. Signal-to-noise ratio (S/N or SNR) The ratio of noise to picture signal information - usually expressed in dB. Digital source equipment is theoretically capable of producing pure noise-free images, which would have an infinite signal to noise ratio. But these, by reason of their purity, may cause contouring artifacts if processed without special attention - a reason for Dynamic Rounding. A rule of thumb to express the realistic signal to noise capability of a digital system is given by the expression: S/N (dB) = 6N + 6 Where N is the number of bits. Hence an 8-bit system gives 54 dB S/N. This would be the noise level of continuous LSB dither and would only be produced over the whole picture by digitizing a flat field (i.e. equal grey over the whole picture) set at a level to lie midway between two LSBs. Other test methods give a variety of results, mostly producing higher S/N figures. Simul-casting The term used to describe the simultaneous transmission of analogue 4:3 and digital 16:9 for the same service. Both versions are transmitted frame accurately at the same time to ensure that no viewer is disadvantaged. SMPTE Society of Motion Picture and Television Engineers; It has within its structure a number of committees which make recommendations (RP 125 for example) to the ITU-R and to ANSI in the USA. SOAP SOAP is a protocol for exchanging XML-based messages over a computer network, normally using HTTP. SOAP forms the foundation layer of the web services stack, providing a basic messaging framework that more abstract layers can build on. SOAP facilitates the Service- Oriented Architectural Pattern. There are several different types of messaging patterns in SOAP, but by far the most common is the Remote Procedure Call (RPC) pattern, where one network node (the client) sends a request message to another node (the server), and the server immediately sends a response message to the client. Note: SOAP originally was an acronym for Simple Object Access Protocol, but the acronym was dropped in Version 1.2, and is now simply referred to as SOAP. Glossary of Terms 51 proxivision media

Solution Specific Technology The free application of both software and hardware to a specified task. This will involve evaluation of the task and using any available technology to provide the optimum solution. For fast operation of high quality image handling and processing equipment for film and television, this usually involves building dedicated hardware and writing special software. SRAM Static random access memory. This type of memory chip in general behaves like dynamic RAM (DRAM) except that static RAMs retain data in a six transistor cell needing only power to operate (DRAMs require clocks as well). Because of this, current available capacity is lower than DRAM - and costs are higher, but speed is also greater. Standard Definition Standard Definition, sometimes referred to as standard def or SD, is a picture that has less picture information associated to it than that of HD, i.e. lower pixel count, line count, smaller aspect ratio, etc. The aspect ration for SD is generally 4:3, though you may come across SD in picture box (16:9) this is normally accomplished by cropping pixels out of the image, not adding pixels to increase the aspect ration to 16:9. Storage capacity (for video) Using the ITU-R 601 4:2:2 digital coding standard, each picture occupies a large amount of storage space - especially when related to computer storage devices such as DRAM and disks. So much so that the numbers can become confusing unless a few benchmark statistics are remembered. Fortunately the units of mega, giga and tera make it easy to express the vast numbers involved; 'One gig' trips off the tongue far more easily than 'One thousand million' and sounds less intimidating. Storage capacities for video can all be worked out directly from the 601 standard. Bearing in mind that sync words and blanking can be re-generated and added at the output, only the active picture area need be stored. In line with the modern trend of many disk drive manufacturers, here kilobyte, megabyte and gigabyte are taken as 103, 106 and 109 respectively. Every line of a 625/50 TV picture has 720 luminance (Y) samples and 360 each of two chrominance samples (Cr and Cb), making a total of 1,440 samples per line. As there are 576 active lines in each 625-line picture this gives 1440 x 576 = 829,440 pixels per picture. Sampled at 8 bits per pixel a picture is made up of 6,635,520 bits or 829,440 8-bit bytes - generally written as 830 KB. With 25 pictures a second there are 830 x 25 = 20,750 kbytes or 21 Mbytes per second. The 525/60 picture has 487 active lines so there are 1,440 x 487 = 701,280 pixels per picture. With each pixel sampled at 8-bit resolution this creates 5,610,240 bits, or 701.3 kbytes. With 30 frames per second this creates a total of 21,039 kbytes, or 21 Mbytes. Note that both 625 and 525 line systems require approximately the same amount of storage for a given time - 21 Mbytes for every second. To store one hour takes 76 Gbytes. Looked at another way each Gigabyte (GB) of storage will hold 47 seconds of non-compressed video. If compression is used, simply divide or multiply the numbers by the compression ratio. For example, with 5:1 compression 1 GB will hold 47 x 5 = 235 seconds, and 1 hour takes 76/5 = 18 GB (approx) Glossary of Terms 52 proxivision media

Sub-pixel A spatial resolution smaller than that of pixels. Although digital images are composed of pixels it can be very useful to resolve image detail to smaller than pixel size, ie sub-pixel. For example, the data for generating a smooth curve on the screen needs to be created to a finer accuracy than the pixel grid itself - otherwise the curve will look jagged. Again, when tracking an object in a scene or executing a DVE move, the size and position of the manipulated picture must be calculated, and the picture resolved, to a far finer accuracy than the pixels - otherwise the move will appear jerky. Moving an image with sub-pixel accuracy requires picture interpolation, as its detail that was originally placed on lines and pixels now has to appear to be where none exist. It has to be effectively rendered onto an intermediate pixel/line position. The example of moving a picture down a whole line is achieved relatively easily by re-addressing the lines of the output. But to move it by half a line requires both an address change and interpolation to take information from the adjacent lines and calculate new pixel values. Good DVEs work to a grid many times finer than the line/pixel structure of 601. Switch Like a bridge, a switch connects networks and filters packets, only sending on packets to a given network segment if they’re addressed to a device on that segment. Also like a bridge, your basic switch generally operates at OSI Layer 2. T: Table 2 (ATSC) Digital television offers new opportunities for the delivery of audio to the home. The digital audio compression system documented in the ATSC standard for Digital Television is AC-3. Table 2, Annexe B of this document shows the range of services catered for. The services may contain complete programme mixes or only a single programme element. Potentially this means that a viewer can choose from a wide range of audio services as long as the receiver has the capability of decoding them. Glossary of Terms 53 proxivision media

Type of service (audio) 0 Main audio service: complete main (CM) 1 Main audio service: music and effects (ME) 2 Associated service: visually impaired (VI) 3 Associated service: hearing impaired (HI) 4 Associated service: dialogue (D) 5 Associated service: commentary (C) 6 Associated service: emergency (E) 7 Associated service: voice-over (VO) Table 3 (ATSC) Table 3 of the ATSC DTV Standard, Annex A, summarizes the picture formats allowable for DTV transmission in the USA. Any one of these may be compressed and transmitted. An ATSC receiver must be able to display pictures from any of these formats. Picture formats Legend Aspect Ratio: 1= square samples, 2 = 4:3 display aspect ratio, 3 = 16:9 display aspect ratio Frame Rate: 1 = 23.976 Hz, 2 = 24 Hz, 4 = 29.97 Hz, 5 = 30 Hz, 7 = 59.94, 8 = 60Hz Vertical Scan: 0 = interlaced scan 1 = progressive scan * Note that 1088 lines are actually coded in order to satisfy the MPEG-2 requirement that the coded vertical size be a multiple of 16 (progressive scan) or 32 (interlaced scan). The wide range of formats in Table 3 caters for schemes familiar to television and computers and takes account of different resolutions, scanning techniques and refresh rates. Although each has its own application and purpose, some of the combinations are more familiar than others. Targa (.TGA) An image file format widely used in computer systems. It was developed by Truevision Inc. originally for use with PCs but is now widely used with Macs as well. TBC TimeBase corrector. This is often included as a part of a VTR to correct the timing inaccuracies of the pictures coming from tape. Early models were limited by their dependence on analogue storage devices, such as glass delay lines. This meant that VTRs, such as the original quadruplex machines, had to be mechanically highly accurate and stable to keep the replayed signal within the correction range (window) of the TBC - just a few microseconds. The introduction of digital techniques made larger stores economic so widening the correction window and reducing the need for specially accurate mechanics. The digital TBC has had a profound effect on VTR design. Glossary of Terms 54 proxivision media

TCP/IP Transfer Control Protocol/Internet Protocol. A set of standards that allows the transfer of data between computers. Besides its application directly to the Internet it is also widely used throughout the computer industry. It was designed for transferring data files rather than television or film pictures which are large - 1 MB or more each. Thus although TCP/IP has the advantage of being widely compatible it is a relatively inefficient way of moving picture files. TIFF (.TIF) Tagged Image File Format. A bit-mapped file format for scanned images - widely used in the computer industry. It originated for use with PCs but now is also used in Macs. Tracking (image) Following a defined point, or points, in a series of pictures in a clip. Initially this was performed by hand, using a DVE. Not only was this laborious but it was also difficult, or impossible to create sufficiently accurate results - usually due to the DVE key frame settings being restricted to pixel/line accuracy. More recently image tracking has become widely used, thanks to the availability of automatic point tracking operating to sub-pixel accuracy. Used within an integrated system the tracking data can be applied to control DVE picture moving for such applications as removal of film weave, replacing objects in moving video etc. Token Ring Method to administer a network to ensure it is clear before transmitting a message. A single 'token' is continuously passed around the network and only the node that has it can transmit. Two forms exist - standard token loop (as above) and Early Token Release, where the token is attached to the end of the transmitted message so creating a train of data within the loop. TrueType (fonts) The TrueType vector font format was originally developed by Apple Computer, Inc. The specification was later released to Microsoft. TrueType fonts are therefore supported on most operating systems (including Apple and Microsoft). Most major type libraries are available in TrueType format. There are also many type design tools available to develop custom TrueType fonts. Quantel equipment supports the import of these and other commercially available fonts. Glossary of Terms 55 proxivision media

True Random Access The ability to continuously read any frame in any order at or above video (or real-time) rate. A true random access video store (usually comprising disks) allows a whole new way of editing, totally free from the restrictions of linear working. At the same time problems associated with fragmentation do not arise, ensuring full operation at all times - particularly important for servers. Truncation Removal of the least significant bits (LSB) of a digital word - as could be necessary when connecting 10-bit into 8-bit equipment, or handling the 16-bit result of a digital video mix. If not carefully handled it can lead to unpleasant artifacts on video signals. Quantel invented Dynamic Rounding to handle the truncation of digital video. U: Uncommitted editing Editing where the decisions are made and the edits completed but any can still be easily changed. This is only possible in a true random access edit suite where the edits need only comprise the original footage and the edit instruction. Nothing is re-recorded so nothing is committed. This way, decisions about any aspect of the edit can be changed at any point during the session, regardless of where the changes are required. Up-Resing The process which increases the number of pixels used to represent an image by interpolating existing pixels to create new ones at closer spacing. Despite its name the process does not increase the resolution of the image. Glossary of Terms 56 proxivision media

V: Vapourware Software or hardware that is promised or talked about but is not yet completed - and may never be released. Variable Bit Rate The term variable bit rate (VBR) is a term in telecommunications Quality of Service (QoS). Compare with constant bit rate. An MP3 file can be recorded with a variable bitrate from 8–320 Kbit, a lower rate will save storage. When referring to codecs, variable bit rate encoding varies the amount of output data in each time segment based on the complexity of the input data in that segment. The goal is to maintain constant quality instead of maintaining a constant data rate. VBR is preferred for storage (as opposed to streaming) because it makes better use of storage space: More space is allocated to more complex segments while less space is allocated to less complex segments. MP3, WMA, and Vorbis files can optionally be encoded with VBR. Vector fonts Fonts that are stored as vector information - sets of lengths and angles to describe each character. This offers the benefits of using relatively little storage and the type can be cleanly displayed at virtually any size. However it does require that the type is RIPped before it can be used - requiring significant processing power if it is to be used interactively for sizing and composing into a graphic. Video codec A video codec is a device or software module that enables the use of compression for digital video. The compression usually employs lossy data compression. Historically, video was stored as an analog signal on magnetic tape. Around the time when the compact disc entered the market as a digital-format replacement for analog audio, it became feasible to also begin storing and using video in digital form and a variety of such technologies began to emerge. Audio and video call for customized methods of compression. Engineers and mathematicians have tried a number of solutions for tackling this problem. There is a complex balance between the quality of the video, the quantity of the data needed to represent it (also known as the bit rate), the complexity of the encoding and decoding algorithms, robustness to data losses and errors, ease of editing, random access, the state of the art of compression algorithm design, end-to-end delay, and a number of other factors. VITC Vertical Interval Timecode. Timecode information in digital form, added into the vertical blanking of a TV signal. This can be read by the video heads from tape at any time pictures are displayed, even during jogging and freeze but not during spooling. This effectively complements LTC ensuring timecode can be read at any time. Glossary of Terms 57 proxivision media

Virtual Private Network (VPN) A Virtual Private Network, or VPN, is a secure communications network usually used within a company, or by several different companies or organizations, to communicate over a public network. VPN message traffic is carried out over a public networking infrastructure (e.g. the Internet) using standard (often insecure) protocols. Generally, a firewall sits between a remote user's workstation or client and the host network or server. The firewall may pass authentication data to an authentication service in a host network. A known trusted person with privileged /rights based access is allowed to access resources not available to unauthorized users. VSB Vestigial Sideband Modulation - refers to the characteristics of the RF/Transmission subsystem of the Digital Television Standard. The VSB system offers two modes: a terrestrial broadcast mode - 8 VSB - with 8 discrete amplitude levels supporting a payload data rate of 19.28 Mb/s in a 6 MHz channel, and a high data rate mode - 16 VSB - with 16 discrete amplitude levels supporting a payload of 38.57 Mb/s. The high data rate mode trades off transmission robustness for payload data rate. W: Wide Area Network (WAN) A wide area network or WAN is a computer network covering a wide geographical area, involving a vast array of computers. This is different from personal area networks (PANs), metropolitan area networks (MANs) or local area networks (LANs) that are usually limited to a room, building or campus. The best example of a WAN is the Internet. WANs are used to connect local area networks (LANs) together, so that users and computers in one location can communicate with users and computers in other locations. Many WANs are built for one particular organization and are private. Others, built by Internet service providers, provide connections from an organization's LAN to the Internet. WANs are most often built using leased lines. At each end of the leased line, a router connects to the LAN on one side and a hub within the WAN on the other. Network protocols including TCP/IP deliver transport and addressing functions. WAV An audio file format developed by Microsoft that carries audio that can be coded in many different formats. Metadata in WAV files describes the coding used. To play a WAV file requires the appropriate decoder to be supported by the playing device. Wavelet A compression technique in which the signal is broken down into a series of frequency bands. This can be very efficient but, as the processing is slow, it is not well suited to video. Widescreen A TV picture display that has a wider aspect ratio than the normal 4:3 and uses the normal 525/60 or 625/50 line/field scans. Widescreen 16 x 9 is also the aspect ratio used for HDTV. The widescreen aspect ratio is usually 16:9 but there are some intermediate schemes, such as 14:9. Widescreen is used on some analogue transmissions as well as many digital transmissions. Winchester disks A particular form of hard disk in which several disk platters and their associated heads are sealed within a case in a clean room. They offer very reliable operation with MTBFs of 1,000,000 hours - and more. The absence of dust allows the read/write heads to be kept very close to the disk surface (closer than the size of an average dust particle) which means the data can be packed much more tightly than would otherwise be possible. This technology is a part of the continuing development of disks. Glossary of Terms 58 proxivision media

Word clock Clock information associated with AES/EBU digital audio channels. Synchronous audio sampled at 48 kHz is most commonly used in TV. The clock is needed to synchronize the audio data so it can be read. WORM Write Once/Read Many - describes storage devices on which data, once written, cannot be erased or re-written. Being optical, WORMs offer very high recording densities and are removable making them very useful for archiving. WYSIWYG What You See Is What You Get. Usually, but not always, referring to the accuracy of a screen display in showing how the final result will look. For example a word processor screen showing the final layout and typeface that will appear from the printer. X: XML The Extensible Markup Language (XML) is a W3C-recommended general-purpose markup language for creating special-purpose markup languages, capable of describing many different kinds of data. It is a simplified subset of SGML. Its primary purpose is to facilitate the sharing of data across different systems, particularly systems connected via the Internet. Languages based on XML are defined in a formal way, allowing programs to modify and validate documents in these languages without prior knowledge of their form. XML Content Server An XML content server is a platform that provides a set of services used to build applications and support business processes based on content. XMP The eXtensible Metadata Platform or XMP is a specific type of markup language used in photo editing applications. First introduced by Adobe Systems in April 2001 as part of their Adobe Acrobat version 5.01 program, Adobe subsequently released the definition into the public domain and XMP is now an open source standard. Y: Y, Cr, Cb The digital luminance and color difference signals in ITU-R 601 coding. The Y luminance signal is sampled at l3.5 MHz and the two color difference signals are sampled at 6.75 MHz co-sited with one of the luminance samples. Cr is the digitized version of the analogue component (R-Y), likewise Cb is the digitized version of (B-Y). YIQ Convenient shorthand commonly - but incorrectly - used to describe the analogue luminance and color difference signals in component video systems. Y is correct for luminance but I and Q are the two sub-carrier modulation axes (I - In-phase and Q - Quadrature) used in the NTSC color coding system. Scaled and filtered versions of the R-Y and B-Y color difference signals are used to modulate the NTSC sub carrier in the I and Q axes respectively. The confusion arises because I and Q are associated with the color difference signals but clearly they are not the same thing. Glossary of Terms 59 proxivision media

Y, (R-Y), (B-Y) These are the analogue luminance, Y, and color difference signals (R-Y) and (B-Y) of component video. Y is pure luminance information whilst the two color difference signals together provide the color information. The latter are the difference between a color and luminance: red - luminance and blue - luminance. The signals are derived from the original RGB source (eg a camera or telecine). The Y, (R-Y), (B-Y) signals are fundamental to much of television. For example in ITU-R 601 it is these signals that are digitized to make 4:2:2 component digital video, in the PAL and NTSC TV systems they are used to generate the final composite coded signal and in DTV they are sampled to create the MPEG-2 video bitstreams. YUV Convenient shorthand commonly - but incorrectly - used to describe the analogue luminance and color difference signals in component video systems. Y is correct for luminance but U and V are, in fact, the two sub-carrier modulation axes used in the PAL color coding system. Scaled and filtered versions of the B-Y and R-Y color difference signals are used to modulate the PAL sub-carrier in the U and V axes respectively. The confusion arises because U and V are associated with the color difference signals but clearly they are not the same thing. ## END## Glossary of Terms 60 proxivision media

Glossary Of Terms

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