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capabilities – repeaters, bridges, etc. The data transmission rate is 10, 100 Mb/s up to 1 and 10 Gb/s, but overheads in packaging data and packet separation mean actual throughput is less than the ‘wire speed’ bit rate. There are many connection methods for Ethernet varying from copper to fiber optic. Currently the three most common are: 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. Gigabit Ethernet (GigE) Development of existing Ethernet technology to support 1,000 Mb/s. This is specified for both fiber and copper Cat. 5e. 10 Gigabit Ethernet (10GigE) only functions over copper for short distances – 15 meters using twinax cable. Using augmented cat. 6 (Cat 6A) cable it may travel twice that distance. For longer range optical fiber is the only answer. This only operates in full-duplex mode – so collision detection protocols are unnecessary. But the packet format and other current Ethernet capabilities are easily transferable to 10GigE. 100 Gigabit Ethernet (100GigE) continues the x10 steps of Ethernet data speed evolution. Destined to travel over optical fiber, it is at the development stage but will doubtless emerge into the commercial world sometime soon. See also: Hub, CSMA/CD, Switch Websites: www.ethernetalliance.org www.ethermanage.com/ethernet/ethernet.html

ETSI The European Telecommunications Standards Institute. Its mission is to produce lasting telecommunications standards for Europe and beyond. ETSI has 655 members from 59 countries inside and outside Europe, and represents administrations, network operators, manufacturers, service providers, research bodies and users. See: Appendix Website: www.etsi.org

ETSI compression

A compression technique, based on DCT. Unlike MPEG, which is asymmetrical having complex coders and simpler decoders and is designed for broadcast, this is symmetrical with the same processing power at the coder and decoder. It 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 milliseconds against around a second, enabling interviews to be conducted over satellite links without unwarranted delays. Data rate is 34 Mb/s.

eVTR

A colloquial term for a Sony IMX VTR with an Ethernet connection. See also: D10

EXOR

The mathematical operation of EXclusive ORlogic gate on a numberof data bits. Forexample the EXOR of two bits is 1, only if 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. See also: Error detection

Exposure

Exposure refers to the amount of light that falls on a film or light sensor. In a camera this is controlled by both time with the shutter, and the effective lens aperture, referred to as the F-number or T number. See also: Density, Stop

FAN

File Area Networks are a shared storage concept that stores shared files in multiple locations. Website: http://en.wikipedia.org/wiki/File_Area_ Network

Fibre Channel (FC)

An integrated set of standards developed by ANSI designed to improve data speeds between workstations, supercomputers, storage devices and displays while providing a single standard for networking storage and data transfer. It can be used point-to-point, switched or in an arbitrated loop (FC-AL) connecting up to 126 devices. See also: SAN Website: www.fibrechannel.org

File-based (media)

‘File-based’ generally refers to storing media in files rather than as continuous streams – like video tape. The term is more widely used to describe IT-based environments for handling and processing digital media. The future of media production is seen as being file-based.

File transfer

A discontinuous transfer process which treats each transferred item as a single block, neither divisible into smaller, independent elements nor part of a larger whole. As the transfer process has a recognizable beginning and end (unlike streaming) it is possible for the complete transfer to be checked and any errors corrected. This is not possible with a streaming process. File transfer requires material to be complete and clearly identifiable. When handling time-based material, such as video and audio this the complete file has to be available before transfer can start. If the whole clip is a single file, this cannot be transferred until all the material is complete. However, if the clip is sub-divided, for example into frames, the transfer can start immediately after the first frame is completed. This becomes important in time sensitive applications such the live editing of highlights while the event is still taking place. See also: Streaming

Film formats

Unlike pre-HD television, which had only two image formats, 525/60I and 625/50I, 35 mm film has many. Of these the most common are Full Frame, which occupies the largest possible area of the film, Academy and Cinemascope. The scanning for these is defined in the DPX file specification as follows: F These scan sizes generally represent the valid image size within the total frame size indicated by full frame. It is generally considered that all scanning is done at full frame size as this avoids the complexity of adjusting the scanner optics or raster size with risks associated with repeatability and stability. Although these digital image sizes came about as formats for scanning film, new digital cinematography cameras are also using them, exactly or nearly. In the file-based world of DI the exact size does not matter, as long as it’s managed correctly and, most importantly, able to produce high quality output for release prints and digital cinema – where the DCI specifies exact sizes.

2K has 3.19 M pixels and a 1.316:1 aspect ratio. It is used for digitizing full frame 35mm motion picture film sampled in 4:4:4 RGB color space – making each image 12 MB. Sampling is usually at10-bit resolution and may be linear or log, depending on the application, and is progressively scanned. Note that the sampling includes 20 lines of black between frames because of the use of a full frame camera aperture. Thus the actual ‘active’ picture area is 2048 x 1536, has a 4:3 aspect ratio and is exactly QXGA computer resolution.

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GLOSSARY OF TERMS