European Broadcasting Union. An organization comprising European broadcasters which co-ordinates the production and technical interests of European broadcasting. It has within its structure a number of committees which make recommendations to ITU-R.
See also: ITU
ErrorCheckand 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.
See also: Checksum, CRC
Edit Decision List. A text file describing the make up of a program by defining the shots to be used , their inpoints, duration and sequence. EDLs can be produced during an off-line editing 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. News journalists working with integrated news production systems, such as Quantel’s Enterprise sQ news systems, can effectively create EDLs at their desktops.
EDLs have been frozen in time and not kept pace with the continued development of post production. They do not carry information on DVEs, complex color correction, layering, keying etc., or carry other data about ownership, rights, etc. The development of AAF has filled these gaps. There has however been some extension to the original format to allow simple color corrections to be defined by creating the CDL which combines the edit timings of the EDL with basic color controls for Offset, Gain, Gamma and Saturation for RGB data – 10 parameters in total.
See also: AAF, CDL, Conform, OMFI
Digital effects processes have replaced the traditional film optical effects. With their faster, more accurate interactive workflow, digital effects are widely used, typically in drama productions for movies and for television. With many effects being completed within the of the main post production workflow, it is only the more complex shots that are completed at separate workstations.
Digital effects can retain the full original image quality irrespective of the number of layers used, provided that the images remain in an uncompressed format. The results can usually be seen immediately, making the process interactive and so allowing quick refinements to complete the desired result. All this is available to be seen in context with the rest of the production, providing immediate checks for continuity. As digital effects are relatively quick and accessible, they now play a much larger role in productions.
DTV allows broadcasters to transmit electronic program guides. For many, this service is considered essential to keep viewers up to date with, and enable them to navigate between, the large number of channels that DTV services can deliver. The program guide database allows a receiver to build an on-screen grid of program information and contains controls to ease navigation.
Audio that is carried within a video stream such as SDI – so simplifying cabling and routing. The standard SMPTE 272M allows embedding up to four groups each of four mono audio channels in SD-SDI. For HD the standard is SMPTE 299M. Both can carry up to 16 channels of audio (8 pairs). SMPTE 299-2:2010 extends audio capacity over 3G SDI to 32 channels.
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 locked to the associated video. For example in SD this means 1920 samples per frame in 576/50I, or 8008 samples per five frames in 480/59.94I. 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).
See also: 1000/1001
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 and is found on satellite, cable and terrestrial broadcast systems. Encryption and content security are vital to the growth of digital media markets where copies can be perfect clones of the owners’ valuable assets.
Electronic Newsgathering. Term applied to a small portable outfit, with a broadcast quality TV camera, recorder and/or microwave link, usually used for news. The term was originated to distinguish between newsgathering on film and video tape (electronic) and it now lives on in the chip/card plugable storage era.
See also: ING
A point in a coded video 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.
No means of digital recording is perfect. Magnetic tape, disks and even perhaps SD (chips) suffer from a few marginal areas where recording and replay is difficult or even impossible. However the errors can be detected and some remedial action taken by concealment or correction. The former attempts to hide the problem by making it less noticeable whereas the latter actually corrects the error so that perfect data is output.
When the recorded data is an image, an error can simply be concealed by using data from previous or following TV lines, fields or frames. The result is not guaranteed to be identical to the original but the process is relatively simple and, as important, quick. If the stored information is from a database, a computer program or from special image processing, then 100% accuracy of data is essential. This can be ensured by recording data in a manner where any errors can be detected and the correct data calculated from other information recorded for this purpose. This is error correction.
A difference between computer systems and TV is that the latter is continuous and cannot wait for a late correction. Either the correct result must be ready in time or some other action taken, the show must go on, placing a very tight time constraint on any TV-rate error correction. In contrast, a computer can usually afford to wait a few milliseconds.
Digital VTRs monitor the error rate and provide warnings of excessive errors, which although not immediately visible, may build up during multiple tape passes.
Although error rates from disks are generally many times lower than those expected from digital videotape, they can still occur. To protect against this there is data redundancy and the replay of all data is checked. If an error is detected there is sufficient additional information stored to calculate and substitute the correct data. The total failure of a disk drive can be covered and the missing data re-generated and recorded onto a new replacement, making the system highly accurate and very secure.
See also: ECC, EXOR, RAID
The material that television programs are made of. In other words, the video, audio and any other material such as graphics and captions that are added to make up the final result.
See also: AAF
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 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
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.
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.
The mathematical operation of ‘EXclusive OR’ logic gate on a number of data bits. For example the EXOR of two bits is 1, only if one of them is 1 and the other 0. 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 refers to the integral amount of light that falls on a film or light sensor. In a camera this is controlled by both the shutter open time, and the effective lens aperture, referred to as the F-stop number or T number.
See also: Density, Stop