To use the glossary, simply click below on the first letter of the term of interest:

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

M

Mbps (Mb/s)

Megabits (millions of bits) per second. One megabit contains 1,048,576 bits ( 2 ²⁰ bits)

MBps (MB/s)

MegaBytes (millions of bytes or octets) per second. One megabyte contains 1,048,576 bytes ( 2 ²⁰ bytes)

MC

Multi-Carrier, part of modern data transmission modulation schemes, used by GFSK, Bluetooth, etc.

MCS (broadcasting)

Multipoint Communications System. An MMDS variant, sometimes called "wireless cable TV", a technology to provide television, and sometimes simplex or full duplex data services to areas where customer separation makes wired systems uneconomic. When used with a return audio channel, useful for distance learning. Operates between 2-6 GHz and above 20 GHz depending upon circumstances.

MCS

Teleconferencing use: Multipoint Conference Service

MCU

Multipoint Control Unit (which see)

MGCP

Multimedia Gateway Control Protocol.

MHz

MegaHertz, in analog signals, millions of cycles or alternations per second.

MIL-STD-188-131

US Military Nomenclature for H.320 compatible videoconferencing apparatus.

MLP

Multi-Layer Protocol.

MMDS

Multi-channel Multipoint Distribution Service. Sometimes called "wireless cable TV", a technology to provide television, and sometimes simplex or full duplex data services to areas where customer separation makes wired systems uneconomic. When used with a return audio channel, useful for distance learning.

Modem

MOdulator - DEModulator. A device that converts digital signals to a form suitable for analog transmission.

MOS Testing

Mean Opinion Score Testing, a means of evaluating the subjective performance of voice and/or video transmission equipment using procedures as set out in ITU-T P.800 and related standards.

Motion Compensation

see Motion Prediction.

Motion Prediction

A type of interframe coding used by codecs that compress motion video. By examining statistics of previous video frame sequences, a future prediction of the motion vectors and rate-of-change for an object, block or group of pixels is developed for subsequent frames. In H.261, the estimated vectors must terminate within the image while in H.263, they may extend outside the image bounds. Important at lower transmit bit rates, optional in H.261.

MPEG

Motion Pictures Experts Group, an ISO image standards group.

MPEG1

MPEG1 is the first of a family of motion video and audio compression standards. It provides DCT lossy compression with rather high quality. It is intended for broadcast quality applications, with resolutions based upon the CCIR (now ITU-R) 601 standard for video coding. It uses three coding protocols: Intraframe coding or I-Pictures (no prediction), P-Pictures, incorporating motion prediction from the previous video image and, B-Pictures (bi-directional prediction) which include motion prediction one frame ahead as well as from the previous frame. MPEG2 has largely supplanted MPEG1.

MPEG2

MPEG2 is the second in a family of motion video and audio compression standards. The result of a natural evolution from MPEG1, it provides DCT lossy compression ranging from low to rather high quality although not as good as MPEG1. It is intended for broadcast quality applications, with resolutions based upon the CCIR (now ITU-R) 601 standard for video coding. It uses three coding protocols: Intraframe coding or I-Pictures (no prediction), P-Pictures, incorporating motion prediction from the previous video image and, B-Pictures (bi-directional prediction) which include motion prediction one frame ahead as well as from the previous frame. MPEG2 also has a coding mode at 24 frames per second, matching that of motion picture film, useful for offline image encoding. MPEG2 has largely supplanted MPEG1 and is used for coding multimedia images from CD-ROM, DVD, broadcasting, pay TV and high quality videoconferencing. MPEG2 also includes more coding decision points than MPEG1, permitting rather fine control of image quality over time in response to the needs of other channels in applications like DBS.

This standard is also known as ITU-T H.262

MPEG3

The MPEG3 standard was intended as an ultra-high quality solution that was abandoned during development, and therefore does not exist. However, the term "MPEG3" is sometimes incorrectly used to describe MPEG2 layer 3 audio (MP3).

MPEG4

MPEG4 is an ISO standard intended to satisfy the needs of content authors, network service providers and end users. It is a multifaceted, extensible standard, and is an attempt to provide all things to all people. It covers sprites, speech synthesis, streaming video, multimedia and many other aspects including a foreground-background coding technique which will likely supplant MPEG2 for broadcast applications as it uses about one-half the bandwidth for equivalent quality. The most common version found in the PC environment is known as MPEG4 Part 3 which includes moving images and sound.

MPEG4 Part 10 AVC

An ISO motion-video compression standard using advanced video coding, a foreground-background coding technique, intended for high-quality and HDTV applications. The ISO work was merged with that of ITU-T work on same subject and is known as H.264 (which see).

MSDSL

Multi-rate Symmetrical Digital Subscriber Line, MSDSL provides full duplex symmetrical connectivity at bit rates up to 2.0 Mbps over distances up to 8.8 Km (5.5 miles) over a single pair of telephone wires. The service provider or carrier has the capability of setting the maximum bit rate for the line, often linked to the monthly line charges. This type of transmission does not support telephony over the same physical pair as does ADSL.

MTBF

Mean Time Between Failures, a measure of system or hardware reliability or availability.

MTTR

Mean Time To Repair. Especially useful for in complex systems, MTTR provides a mean time from the onset of a failure to return to pre-failure operational status.

Multiplex (verb)

To sequentially incorporate several data streams into a single data stream in such a manner that each may later be recovered intact.

Multipoint Control Unit (MCU)

A device to link three or more videoconference locations for fully interactive audio, data and video teleconferencing. An ITU-T compatible MCU must meet the requirements of H.231 and H.243. In addition, the T.12x and T.13x suites of standards, desirable for both codec and MCU, provide greater functionality for multipoint videoconferencing.

MVDS

Multichannel Video Distribution System. Sometimes called "wireless cable TV", a technology to provide television, and sometimes simplex or full duplex data services to areas where customer separation makes wired systems uneconomic. When used with a return audio channel, useful for distance learning. Operates between 2-6 GHz and above 20 GHz depending upon circumstances.

MWS

Multipoint Wireless System. Another name for MMDS (which see). Sometimes known as "wireless cable", a technology to provide television, and sometimes simplex or full duplex data services including Internet and VoIP to areas where customer separation makes wired systems uneconomic. When used with a return audio channel, useful for distance learning. Operates between 2-6 GHz and above 20 GHz depending upon circumstances.

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