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Internet Terminology - M-Z

A block of 16 x 16 pixels. Used in MPEG for motion compensation prediction.

Mbit/s (Megabit per second)
A digital transmission speed of millions of bits per second.

Mbps (Megabits per second)
Equivalent to one million bits per second.

Media Server
A server designed for transmitting multimedia data.

Data streaming at 256 Kbps up to 1.5 Mbps, supporting 15 frames per second of full-motion video and 320x240 resolution (similar to MPEG-1 data streams).

a method of compression where each frame or field in a video signal is compressed using JPEG.

Moiré Pattern
The name for the spurious pattern caused by interference between two periodic structures in the image (e.g. a grid in the scene interfering with scanning lines or dot pattern in the camera), or caused by interference in a composite video signal between the color carrier and the luminance information.

Motion Compensation
A video compression technique that makes use of the redundancy between adjacent frames of motion video.

Motion Estimation
The technique of calculating and predicting movements of image elements, normally expressed as a series of motion vectors. MPEG Moving Pictures Experts Group (or often Motion Picture Experts Group); a working group under ISO/IEC and its set of standards for coding of moving pictures and associated audio. Standards are the MPEG-1 and the MPEG-2.

Motion Video
Video which displays real motion. It is accomplished by displaying a sequence of images (frames) rapidly enough that the eye sees the image as a continuously moving picture.

Moving Picture Experts Group (MPEG)
An ISO body focused on the development of digital compression algorithms for motion video.

Acronym for “Motion Picture coding Expert Group,” a work group of the ISO-IEC Joint Technical Committee 1, responsible for developing a standard algorithm for the compression of motion video.

Compressed audio and video bit stream designed to fit into a bandwidth of 1.5 Mbps - the same data rate of audio CD’s , single-speed CD-ROMs, and digital audio tape (DAT). The systems component of the standard enables integration of audio and video streams with the corresponding timestamp to allow synchronization of both streams. Most MPEG-1 decoder chips support a level of quality comparable to a VHS videotape of 352x240 resolution at 30 frames per second.

Compressed content that provides broadcast quality video. Transmission rates average 4.0 Mbps.

MPEG-2 Systems
An ISO/IEC standard (13818-1) that defines the syntax and semantics of bit-streams in which digital audio and visual data are multiplexed. MPEG-2 Systems provides a two-layer multiplexing approach. The first layer, called Packetized Elementary Stream (PES), is dedicated to ensure tight synchronization between video and audio. It is a common way for presenting all the different materials that require synchronization (video, audio, and private data). The second layer is dependent on the intended communication medium. The specification for error free environments such a local storage is called MPEG-2 Program Stream, while the specification addressing error prone environments is called MPEG-2 Transport Stream.

Refers to the delivery of information that combines diverse information types and different content formats-motion video, audio, still images, graphics, animation and text chief among them.

The method of blending multiple signals successively to be carried jointly on a communications channel; a time-division interleaving of data packets of separate channels or streams into a single larger stream.

A term used by network designers to describe network links that have many possible endpoints.

In a computer, a technique that allows several processes to appear to run simultaneously even though the computer has only one CPU. Multitasking is done by sequentially switching the CPU between the tasks, usually many times per second.

Placeholder information associated with a single use of a program that can handle multiple concurrent users. From the program's point-of-view, a thread is the information needed to serve one individual user or a particular service request. If multiple users are using the program or concurrent requests from other programs occur, a thread is created and maintained for each of them. The thread allows a program to know which user is being served as the program alternately gets re-entered on behalf of different users. (One way thread information is kept is by storing it in a special data area and putting the address of that data area in a register. The operating system always saves the contents of the register when the program is interrupted and restores it when it gives the program control again.)

Near Video-on-demand (NVOD)
Scheduling of multiple programs, with closely staggered start times, to approximate video-on-demand.

National Television System Committee (NTSC)
analog video format that features a refresh rate of 59.94 Hz fields per second and 29.97 Hz frames per second. NTSC format is used in the United States, Canada, Mexico, and parts of Asia and Latin America.

Near-Instantaneously Companded Audio Multiplex; a standard for digital audio on TV, adopted by several countries. Uses data reduction and is transmitted as a QPSK signal in the video signal.

Unwanted electrical or electromagnetic energy that can degrade the quality of signals and data. Noise occurs in digital and analog systems, and can affect files and communications of all types, including text, programs, images, audio, and telemetry.

Abbreviation for “National Television Systems Committee.” In 1953, this standardizing body created the color television standards for the United States. This system is generally referred to as the NTSC color television system which uses an interlaced 525-line 30-frames per second picture.

On-demand streaming
Streaming media content that is transmitted to the client upon request.

In the motion picture industry, the name for special effects.

Optical Carrier levels (OC-x)
The Synchronous Optical Network (SONET) includes a set of signal rate multiples for transmitting digital signals on optical fiber. The base rate (OC-1) is 51.84 Mbps. OC-2 runs at twice the base rate, OC-3 at three times the base rate, and so forth. Planned rates include OC-1, OC-3 (155.52 Mbps), OC-12 (622.08 Mpbs), and OC-48 (2.488 Gbps). ATM makes use of some of the Optical Carrier levels

Optical fiber (or "fiber optic")
Refers to the medium and the technology associated with the transmission of information as light pulses along a glass or plastic wire or fiber. Optical fiber carries much more information than conventional copper wire and is in general not subject to electromagnetic interference and the need to retransmit signals.

Used in MPEG compression, a predictive algorithm calculates P-frames taking into account information that is common among adjacent frames. The P-frame predicts the difference between the current frame and the closest preceding I or P frame. P-frame is used with I and B frame encoding.

A packet is the unit of data that is routed between an origin and a destination on any packet-switched network. Files are broken into packets for ease of transmission.

Packetized Data
Data such as that representing video that is segmented into small pieces that are, for example, wrapped, labeled, numbered, addressed, error protected so as to survive transit through a heterogeneous or hostile environment; the small pieces are reassembled on completion of their journey.

Acronym for “Phase Alteration Line,”, which is the key feature of the color television system developed in West Germany and used by many other countries in Europe. This system is called the PAL system and uses an interlaced 625-line 25-frames per second picture, except PAL-M (only in Brazil), which uses an interlaced 525-line 30-frames per second picture.

An enhancement of PAL that provides 16:9 aspect ratio and improved picture quality (reduced cross-color and cross-luminance artifacts). A PALplus signal is shown in a letterbox format on a normal PAL TV set.

The actual message, audio data, etc., in a data stream excluding control signals, error checking and other overhead information.

PDU (Protocol Data Unit)
A unit of information (e.g., packet or frame) exchanged between peer layers in a network.

Phase Alteration Line (PAL)
Analog video format standard that features a vertical frequency of 50 Hz, used in most of Western Europe, Australia, and parts of Asia and Latin America.

A single point of an image, having a single pixel value.

Pixel Operation
The process of modifying a pixel value for some specific purpose.

In a digital image, a subjective impairment where the pixels are large enough to become individually visible.

The nodes of a "p" network run at the same nominal frequency, but do so independently (not interlocked). P = "almost synchronous."

A software module which is application-specific and is used in conjunction with another software package.

In video and audio, the process of merging original video and audio from tape or film into a finished program, Post-production includes editing, special effects, dubbing, titling, and many other video and audio techniques.

Pay-per-View; The concept of programming services that are paid for individually.

Predictive Coding
The coding of each pixel by quantizing the difference between its current value and predicted value, computed from past values.

In video, refers to the process of creating programs. In more specific usage, production is the process of getting original video onto tape or film, ready for post-production.

Set of syntax rules defining exchange of data including items such as timing, format, sequencing, error checking, etc.

Also called 3/2 pull-down. The technique for displaying 24 frame-per-second progressive film content on an interlace 30 fame per second monitor. The first frame is show for 3 fields (1.5 frames), and then the second frame is show for 2 fields (1 frame).

Refers to the size of an image, one quarter the size of the Standard Image Format, 176 x 140 pixels for NTSC.

QoS (Quality of Service)
The idea that transmission rates, error rates, and other characteristics can be measured, improved, and, to some extent, guaranteed in advance. QoS is of particular concern for the continuous transmission of high-bandwidth video and multimedia information. Transmitting this kind of content dependably is difficult in public networks using ordinary "best effort" protocols.

Quantization Levels
The predetermined levels at which an analog signal can be sampled as determined by the resolution of the analog to digital converter (in bits per sample) or the number of bits stored for the sampled signal.

The process of converting the voltage level of a signal into digital data after the signal has been sampled.

RAID (redundant array of independent disks)
RAID is a way of storing the same data in different places (thus, redundantly) on multiple hard disks. By placing data on multiple disks, I/O operations can overlap in a balanced way, improving performance. Since multiple disks increases the mean time between failure (MTBF), storing data redundantly increases fault-tolerance.

RAM dump
The process of outputting the contents of a contiguous block of RAM as a sequence of bytes.

In digital memory or mass storage, the ability to access to any point or address without any limitation.

The pattern of motion used in scanning, usually left to right, and repeated over the image from top to bottom as a series of horizontal lines.

Raster Operation
The process of performing a logical operation on a pixel value. Also called raster op.

Real-Time Video (RTV)
In Intel’s DVI technology, the video compression / decompression technique that operates in real-time, using the DVI system itself. Although it produces a picture quality suitable for the multimedia application development process, RTV is normally supplanted by Presentation Level Video (PLV) for the final application.

Remote Control and Navigation System
users need a friendly interface to find their way through all the services offered and communicate their requirements to the central Control System.

To draw an image for display.

A device that regenerates, retimes, and amplifies electrical signals.

Measurement of display image quality in terms of the number of pixels available.

Retrieval Engine
A system embodying software or hardware or both for accessing indexed data from a large mass store such as a CD-ROM.

Return Path
a fully interactive system there needs to be a signal going from the user to the Control System carrying the user's requests.

Red, Green and Blue; a video signal consisting of the three color components red, green and blue. These three colors can be mixed to create any color.

An RGB color value with an additional alpha component representing a relative level of transparency. RGBA color values are typically 32 bits.

RLE (Run Length Encoding)
A compression scheme. A run of pixels or bytes of the same color or value are coded as a single value recording the color or byte value and the number duplications in the run.

A device that sends messages by the best route, especially over large networks.

A host protocol used to request a specific quality of service (QoS) from the network to support an application data stream. RSVP generally enables the reservation of resources along a data path, with built-in interoperability for current and future unicast and multicast routing protocols.

RTCP (Real-Time Control Protocol)
RTCP is the starting point of RTP and controls participants in a session by sending control information for data distribution, monitoring, cross-media, synchronization and sender information.

A transport protocol designed for multiparticipant real-time application services, such as audio and video conferences. Real-tine services such as data acquisition and control may also use the services provided by RTP. Features such as active party identification, demultiplexing, media identification, and playout synchronization are generally available.

Run-Length Coding
A data compression technique that takes advantage of repeated data elements having the same value. Instead of repeatedly coding the same value, the value is coded once along with a count of the number of times to repeat that value.

A type of video signal used in the Hi-8 and S-VHS videotape formats. S-video transmits luminance and color portions separately, using multiple wires. In so doing, S-video avoids the NTSC encoding process and the inevitable loss of picture quality that results from it.

A representative value of a signal at a chosen instant, derived from a portion of that signal.

The process of finding the instantaneous voltage of signal at a specific moment or repetitively at a given rate (the sampling rate).

a wireless, one-way broadcast medium providing no possibility of a Return Path (other than telephone).

The amount of gray (as opposed to hue) in a color, or the intensity of the hue.

The capacity for a computer application or product (hardware or software) to continue to function well as it (or its context) is rescaled (typically, to a larger size, but possibly to a smaller size). The rescaling can be of the product itself (for example, a line of computer systems of different sizes in terms of storage, RAM, and so forth) or in the scalable object's movement to a new context (for example, a new operating system).

Scalable Coding
The ability to encode a visual sequence so as to enable the decoding of the digital data stream at various spatial and/or temporal resolutions. Scalable compression techniques typically filter the image into separate bands of spatial and/or temporal data. Appropriate data reduction techniques are then applied to each band to match the response characteristics of human vision.

Scalable Video
Refers to video compression that can handle a range of bandwidths, scaling smoothly over them.

The process of converting an image into an electrical signal by moving a sensing point across the image usually in a pattern from left to right, and repeated from top to bottom as a series of horizontal lines.

Synchronous Digital Hierarchy; a set of telephone standards that enable synchronous multiplexing of data streams on high-speed links.

Acronym for Séquentiel à mémoire or Système Électronique Couleur avec Mémoire (sequential color with memory). This refers to the color television system developed in France, and used in certain other countries, using an interlaced 625-line 25-frames per second picture. Analog video standard format that displays 625 lines at 50 Hz using a color video-encoding system. SECAM is used in France, Eastern Europe, and Russia.

Server-based video
Refers to video that is streamed from a video server software package.

Set-Top-Box (STB)
A device that converts digitally compressed video input signals; an addressable communications box is needed to decode the signals as they arrive at the television; depending on the system used it may also need to perform functions such as the decompression of the digital signal, or the handling of the Return Path.

Signal-To-Noise Ratio (S/N)
In analog video systems, the ratio between the peak-to-peak black-to-white signal and the rms value of any superimposed noise. IN analog audio systems, S/N refers to the ratio of rms signal to rms noise.

SNMP (Simple Network Management Protocol)
An Internet standard protocol, designed for the management of nodes residing on an IP network.

Synchronous Optical Network; a set of American standards equivalent to SDH. SONET provides standards for a number of line rates up to the maximum line rate of 9.953 gigabits per second (Gbps). Actual line rates approaching 20 gigabits per second are possible. SONET is considered to be the foundation for the physical layer of the broadband ISDN (BISDN).

Spatial Resolution
The number of pixels horizontally and vertically in a digital image.

A serial loop attachment technology that permits as many as 96 disks per adapter to be configured on IBM’s Rs/6000 server platform.

STM (Synchronous Transfer Mode/Synchronous Transport Module)
In ATM, a method of communications that transmits data streams synchronized to a common clock signal (reference clock).

Storage Hierarchy & Control System
even compressed videos require enormous amounts of storage space; the control system must be able to service all the requests coming in.

The real-time transfer of data . In short, the file being dowloaded is viewed at the same time.

Streaming Media
Multimedia content - such as video, audio, text, or animation - that is displayed by a client as it is received from a broadcast network..

Subscriber Management
sophisticated systems for administration, billing and encryption will be required to ensure that the users pay for the services they use and that copyrights are preserved!

SVGA (super video graphics array standard)
This system can support a palette of up to 16,000,000 colors, although the amount of video memory in a particular computer might limit the actual number of displayed colors to something less than that. Image-resolution specifications vary. In general, the larger the diagonal screen measure of an SVGA monitor, the more pixels it can display horizontally and vertically. Small SVGA monitors (14-inch diagonal) usually display 800 pixels horizontally by 600 pixels vertically. The largest monitors (20 inches or more diagonal measure) can display 1280 x 1024, or even 1600 x 1200, pixels.

data communication that requires that each end of an exchange of communication respond in turn without initiating a new communication. A typical activity that might use a synchronous protocol would be a transmission of files from one point to another. As each transmission is received, a response is returned indicating success or the need to re-send. Each successive transmission of data requires a response to the previous transmission before a new one can be initiated.

T-carrier system
The first successful system that supported digitized voice transmission. The original transmission rate (1.544 Mbps) in the T-1 line is in common use today in Internet service provider (ISP) connections to the Internet as well as corporations. Another level, the T-3 line, providing 44.736 Mbps, is also commonly used.

Time Base Corrector; a synchronizer used to remove time base. Errors that result from the mechanical process of recording and playing back on tape.

Transmission Control Protocol/Internet Protocol; This is essentially the Internet’s most common transmission protocol, and can broadly be described as the first-language of the Internet. IP (Internet Protocol) is simply the method for forming and then routing “packets” of data; TCP (Transmission Control Protocol) adds three critical functions:
  1. Packet Sequencing. TCP gives each “packet” of a data a number, so that all packets will be properly reassembled at the receiver.
  2. Reliability. TCP ensures that all “packets” of data sent off actually arrive there by requesting retransmission of the packets if they get lost.
  3. Flow Control. When the Internet becomes clogged, all travelling data is expected to retreat somewhat to allow fair use of the available space. TCP allows the data to do this.

Americanism for telephone company, the provider of telephone services. Often the local supplier rather than the long-distance supplier.

Refers to equipment used for television reproduction of motion picture film or film slides.

A service provided by broadcasters, which allows the viewers at home to receive various information, e.g. programming information. The teletext signal is transmitted as digital data in the VBI.

Temporal Resolution
The ability of the display to reproduce adequate detail to allow the visual system to distinguish the separate parts or components of an object that is moving through the display.

A measure of memory capacity and is two to the 40th power or "roughly" (as a decimal number) a thousand billion bytes (that is, a thousand gigabytes).

Time Code
A system of identifying frames recorded on videotape by assigning each frame a chronological number based on a 24-hour clock.

Token Ring Network
A token ring network is a type of local area network. In a token ring network, all workstations are connected in a ring or star topology and a token-passing scheme is used to prevent the collision between two workstations who want to send messages at the same time.

The process of converting a file from one format to another.

Transmission System
high speed links are required to deliver the vast amounts of information in a timely manner.

One of several data streams being multiplexed into an aggregate data stream.

The communications line between two points or switching systems; mostly the connection between two major switching centers.

Twisted Pair
the most common existing wired system as it is present in millions of telephone lines going to houses, but also the most limited in its bandwidth.

A communications transport protocol layer that is an alternative to the Transmission Control Protocol (TCP) layer. Like TCP, it interfaces with the Internet Protocol (IP) layer. UDP, however, does not provide the data gathering reliability of TCP. For example, it doesn't provide sequencing of the packets that the data arrives in. This means that the application program must be able to provide these services.

Universal Network
The idea of a single network that integrates the existing voice and public telecommunications network (including the Internet), cable TV, data networks, and video broadcast networks so that they work together well.

Variable Data Rate Compression
Techniques designed to produce a data stream with a variable data rate. Such techniques typically maintain a constant level of quantization producing a variable data rate based on the spatial and temporal energy content of the images being encoded.

VBI (Vertical Blanking Interval)
the VBI is the first 22 lines in each field of a PAL signal (15 lines in an NTSC signal). These lines do not contain any video information, but are used for field synchronization purposes (i.e. indicating start of picture). The VBI is also used for transmission of teletext, VITS and VITC.

VBR (Variable Bit Rate)
A form of data delivery where bits are grouped irregularly and will vary with time. Compression that can be delivered at a variable bit rate can adapt to changing network bandwidths as well as to changing properties of a video such as the amount of motion.

Video that can be requested at any time and is available at the discretion of the end user.

VITC (Vertical Interval Time Code)
a form of time code in which the time code is converted to data and placed on a line in the vertical interval of the video signal.

VITS (Vertical Insertion Test Signal)
the VITS signals are test lines inserted in the VBI. The test lines are well defined and have been designed in such a way that most video parameters can be measured. This allows, for example maintenance engineers to test a video link without having to interrupt the service in order to insert a test signal.

A wavelet is a mathematical function useful in signal processing and image compression.

A component video signal consisting of a luminance signal (Y) and two chrominance difference signals (U and V).

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