assess the MTF of film, it is exposed to special test images comprising sine wave bars of successively higher frequencies. The results on the processed film are assessed by measuring its density over microscopically small areas to obtain peak-to-trough values for the different frequencies. These results should then be corrected to allow for the response of the lens, the test film itself and any D/Log E non-linearities. In a practical film system, the film images pass through many components including the camera lens, intermediate stocks and contact printing to the projection lens. Each of these has its own MTF and the system MTF can be calculated as follows. MTFsystem = MTF1 x MTF2 x MTF3 etc… See also: Resolving power
A B C D E F G H I J
K L
M N O P Q R S T U V
W X Y Z
Multimedia The presentation of more than one medium. Strictly speaking TV is multimedia (if you have the sound up). More typically it is pictures (moving and still), sound and often text combined in an interactive environment. This implies the use of computers, with the significant amount of data this requires usually supplied either on CD-ROM or via a data link. ‘Surfing the net’ is an example. High compression ratios are used to allow the use of pictures. One of the first applications was in education; now it is commonly seen at home via the Internet or DVDs. Multimedia has a wide meaning. Another example is in the production of material which is published in many forms. For example pictures from television productions can be transferred to print for listings magazines, to EPGs and to advertising. Such transfers are commonly handled through networking connections. See also: ATM, MPEG, MPEG-4, MPEG-21
Multiplex (Mux) Generally describes a collection of communications channels bundled into one transport system. For example, voice and data co-exist on a phone line carrying conversation and Internet access. In digital television ‘a multiplex’ describes a group of compressed digital video channels multiplexed into single transmission stream occupying the space of one analog terrestrial TV channel. The term ‘Bouquet’ has also been used in this context.
MXF
The Material eXchange Format, SMPTE 377M, is aimed at the exchange of program material between file servers, digital video recorders, editing systems, tape streamers and digital archives, etc. It is a container, or wrapper, format that supports a variety of differently coded streams of essence (images and sound), together with metadata describing the material in the MXF file. See also: AAF Website:
www.mxf.info
NAS
Network Attached Storage is a file server with an operating system that supports the popular file sharing protocols, such as CIFS (Windows) and NFS (Unix). It is accessed as a client on a network such as Ethernet. This is relatively low cost and easy to set up but it is limited by the constraints of the network. If the network is very busy, then access to the NAS will be slower. An alternative form of shared storage can be set up with a SAN that creates its own separate network. See also: SAN Website: www.
techweb.com/encyclopedia
NCS
Newsroom Computer System. The name sprang up when the only computer in a TV news area was used for storing and editing the textual information available from news services. It also created the running order for the bulletin and was interfaced to many other devices around the production studio. See also: MOS
Negative
Film that shows the shot scene as negative images. Various types of negative material are used in several stages of the traditional film production chain that culminates in release prints. See also: Camera negative, Internegative 133
Network layer (1) In TCP/IP, the network layer is responsible for accepting IP (Internet Protocol) datagrams and transmitting them over a specific network. (2) The third layer of the OSI reference model of data communications.
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. See also: IP
Nibble 8 binary bits = 1 Byte 4 binary bits = 1 Nibble; techy humour!
NLE
See Nonlinear (editing) Noise (random)
Irregular level fluctuations of a low order of magnitude. All analog 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. With digital compression, noise has a new importance. Noise, which can originate from analog sources, can be hard to distinguish from real wanted high frequency information. This means compression coders can waste valuable output bandwidth describing the noise to the cost of the real pictures. See also: Dynamic Rounding
Non-additive mix
A mix of two pictures which is controlled by their luminance levels relative to each other, as well as a mix value K (between 0 and 1): e.g. 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, in areas 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. See also: Digital mixing
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 unless it is an exact 30f/s. The mismatch amounts to 1:1000, an 18-frame overrun every 10 minutes. This applies where 59.94, 29,97 or 23.976 picture rates are used in 525/60 systems as well as DTV. See also: 1000/1001, Drop-frame timecode
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GLOSSARY OF TERMS
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