Category Archives: N

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

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

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 be lower than the accuracy of the sampling, i.e. less than one LSB of the digital dynamic range. Pure digitally generated signals however have no 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 at the cost of the the quality of the digital pictures or sound.

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 (lever arm moved half way), 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, amounting to an 18-frame overrun every 10 minutes. This applies where 59.94, 29,97 or 23.976 Hz frame rates are used in video systems, the practice in many ex NTSC countries including USA and Canada.

See also: 1000/1001, Drop-frame timecode

Nonlinear (editing)

Nonlinear 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 recording space, usually using computer disks to store footage. This removes the spooling and pre-rolls needed for VTR operations so greatly increasing the speed of work. Yet greater speed and flexibility are possible with realtime random access to any frame (true random access).

See also: FrameMagic, Linear (editing), On-line (editing), True random access

NRCS

Newsroom Computer System. The name sprang up when the only computer in a TV news area was used for storing and editing the text available from news services. It also created the running order for the bulletin and was interfaced to many other devices around the production studio. Today the NRCS lives on… but it is no longer the only computer around the newsroom! All journalists can access the the NRCS which stores all the video, audio, text needed for them to edit their story at their workstation, which could be anywhere. Also rundowns, prompter scripts and more tasks are undertaken by modern NRCS that may link more systems, such as video editing.

See also: MOS

NTFS

New Technology File System – the standard file system of Windows NT and its descendants Windows 2000 through to Windows 8. It replaced Microsoft’s FAT file system used in MS-DOS and earlier Windows versions. Advantages include improved metadata support, advanced data structures, reliability, disk space use and extensions such as security access control lists (who can access), permitted operations and file system journaling that logs file changes. Full details are a Microsoft trade secret.

NTSC (television standard)

The analog color television system used in the USA, Canada, Mexico, Japan and more, where NTSC M is the broadcast standard (M defining the 525/60 line and field format). It was defined by the NTSC in 1953. With the use of digital TV systems NTSC has become part of broadcasting history.

Note that ‘NTSC’ is often incorrectly used to describe the 525/60 television format even when it is in component or digital form.

NVOD

Near Video On Demand. A service that offers quick access to on-demand program material, sometimes achieved by providing the same program on a number of channels with staggered start times, and so there is not too long to wait for your chosen movie to start. NVOD made sense when programs were only recorded on tape. Now the technology has moved on to computer disk storage, access to programs has hugely improved, so NVOD is no longer needed.

Nyquist (frequency)

The minimum sampling frequency that will faithfully sample an analog signal so it can be accurately reconstructed from the digital result. This is always twice the maximum frequency of the signal being sampled.

Nyquist

In practice significantly higher sampling frequencies are used in order to stay well above the Nyquist frequency, where response drops to zero. This avoids 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 BT.601 the maximum luminance frequency is 5.5 MHz and its sampling frequency is 13.5 MHz. Sin x/x shaped filters are used to counter the attenuation of the sampling system.

See also: 13.5 MHz, Into digits (Tutorial 1), Aliasing