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视音频专业术语表

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视音频专业术语表(13)

2017-02-13 09:15 admin 人关注

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M
M - Mega. A prefix for one million.
MAAP - Mini Architectural Adapter Plates. Compact mountable metal plates available in hundreds of models offering popular pass-through audio, video, phone, data, power, and control connectors. Active MAAPs are also available for power, control, and long distance signal transmission. Along with mounting options for maximum flexibility in placing connectors and controls within reach, these interchangeable components fit together to create an attractive and completely customizable A/V connectivity solution..
MAC - Media Access Control. The Media Access Control data communication protocol sub-layer provides addressing and channel access control mechanisms that make it possible for several terminals or network nodes to communicate within a multi-point network, typically a local area network (LAN). Access to the media may be spread out over time, or as in Ethernet, a mechanism is developed which allows random access, but provides a method for reattempting use of the media if a collision is experienced.
MAC address - Media Access Control. A unique hardware number given to devices that connect to the Internet. When your computer or networking device (router, hub, interface, etc.) is connected to the Internet, a table (see “ARP”) relates the device’s IP address to its corresponding physical (MAC) address on the LAN. Also see "ARP."
Macrobending - A term that describes a macroscopic deviation of an optical fiber’s axis from a straight line due to bending, to the extent that optical loss occurs.
Magnetic deflection - A method of altering the path of an object (such as an electronic beam) with a magnetic field. CRTs have magnetic coils that carry currents that create magnetic fields that control the path of the electron beam. Also called Magnetic focus.
Magnetic focus - See "Magnetic deflection."
Main Cross-Connect – MC - The central portion of a facility's backbone cabling that provides connectivity between equipment rooms, entrance facilities, horizontal cross-connects, and intermediate cross-connects. It usually consists of a distribution of patch panel.
Main Distribution Frame – MDF - A signal distribution frame that connects lines from the outside and lines on the inside.
Matched-Clad Optical Fiber - A singlemode optical fiber with a cladding of uniform refractive index, favored for being less susceptible to bending and splice losses.
Mathematically Lossless Compression - Allows the exact original data to be reconstructed from the compressed data. Data compacting in mathematically lossless processes is between 2:1 and 3:1. The term lossless is in contrast to lossy compression, which only allows an approximation of the original data to be reconstructed in exchange for better compression rates.
Matrix - An electronic device that accepts and distributes video (and/or audio) signals selected from multiple inputs and multiple outputs.Also see "Matrix switcher."
Matrix mixer - Similar to a matrix switcher, but with additional signal processing features, such as equalization (EQ), compression, and level/gain controls on the inputs and outputs.
Matrix switcher - A means of selecting an input source and connecting it to one or more outputs. Like a regular switcher, but with multiple inputs and multiple outputs.
Matte white - A screen with a flat, dull surface for even reflection over wide viewing angles.
MAV - The Extron acronym for matrix audio/video (switcher).
MB - Megabyte. A megabyte is actually 1,048,576 bytes, or roughly 1 million bytes.
MBC - Monitor Breakout Cable. A cable used to view a computer signal on a local monitor or terminal while routing the same signal to a new source, such as a data projector or monitor. An MBC provides three connections in the form of a “Y” cable, a “T” cable, or through a buffer in an enclosure box.
MBC power connector - Some of the Extron MBC high resolution buffers require power. The miniature power plug attached to some MBC cables plugs into the MBC power jack on the interface.
Mbps - Megabits per second. One million bits per second; a unit of measurement for data transmission.
Mechanical splice - A splice between optical fibers accomplished by using a mechanical fixture and an index gel, rather than by thermal fusion.
Media player - A software application used for the playback of audio and video files.
MediaLink™ - Extron's MediaLink System is a family of easy-to-use and inexpensive products that work together to control A/V equipment in any small, one-projector classroom, boardroom, or auditorium.
Megapixel - In digital imaging devices, megapixels define the resolution range when the number of pixels is equal to or greater than 1 million pixels. For example, SXGA is 1280 x 1024, or 1,310,720 pixels. This could be called a 1.3-megapixel device.
Messenger wire - A wire that is used as the supporting element of a suspended aerial cable. This wire may be an integral part of, or external to the cable.
MFTA - Multi-Frequency Termination Adapter. A single termination device with selectable frequencies for different applications.
MHz - Megahertz. One million hertz (cycles per second). Video bandwidth is measured in megahertz.
Microbend - A localized defect in an optical fiber at the core-cladding boundary, caused by mechanical stress that results in sharp, microscopic curvatures in the fiber.
Microbending loss - Loss in an optical fiber due to sharp, microscopic curvatures, caused by imperfections in fiber coating, cabling, packaging, and installation, such as cinching fibers too tightly with a tie wrap.
Micron – μm - A micron, or a millionth (10-6) of a meter.
Mid-Entry - In fiber optics, the opening up of a fiber optic cable mid-span in order to access the fibers inside.
Mid-range - The range of audio frequencies, 250 Hz to 5000 Hz, to which the human ear is most sensitive. Mid-range frequencies give sound its energy.
Military tactical cable - Heavy-duty cable designed for rugged installations in adverse environments.
Milli - m. Abbreviation for one one-thousandth. Example: 1 ms = 1 millisecond or 1/1000 second.
MIMO - Multiple Input Multiple Output antenna technology. In 802.11n. This technology promises to deliver up to 8x coverage and up to 6x speed of current 802.11g networks.
Mini zipcord - A 2.5 mm diameter fiber optic cable with two jacketed fibers that can be separated.
MIPS - Million Instructions Per Second. The rate at which a computer executes instructions.
M-JPEG - Motion JPEG or M-JPEG video compression applies the discrete cosine transform to each video frame independently. No temporal compression is applied in MJPEG and no frame interdependence exists as with MPEG compression. Each video frame is encoded as though it is an MPEG I-frame. Editing and random access are easily facilitated in product designs applying MJPEG.
Modal bandwidth - In fiber optics, the bandwidth-length product, measured in MHz-km, of an optical fiber due to modal dispersion.
Modal dispersion - In fiber optics, the dispersion of a single optical pulse into various modes which arrive at the light receiving device at different times. This limits the performance of multimode optical fiber.
Mode - A path for light within an optical fiber. Singlemode fiber comprises a single path, while in multimode fiber, there are multiple light paths.
Mode Field Diameter – MFD - A measure of the spot size or beam width of light propagating in a singlemode optical fiber. Usually this is 20% larger than the diameter of the core.
Mode filter - A device that removes higher-order modes in multimode fiber.
Modem - Modulator/demodulator. A device that puts information on a carrier signal and transmits it over a (phone) network. The same device receives such signals and demodulates, or separates the information from the carrier. A modem connects computers with other communication devices through ordinary phone lines.
Modulation - The process of adding an information signal to a carrier frequency to allow it to be transmitted. Thus, the carrier is modulated by the information signal, as in a modem.
Moiré - A pattern resulting from a combination of other patterns. In video, this is usually an undesirable pattern caused by an unwanted signal interfering with the desired signal. This may appear as a wavy motion.
Momentary contact - A non-latching contact closure that lasts as long as it is held in place.
Momentary switch - A switch that returns to its normal circuit condition when the actuating force is removed.
Monitor - (1) A TV that receives a video signal directly from an external source, such as a VCR, camera, or separate TV tuner to produce a high-quality picture. (2) A video display used with closed circuit TV equipment. (3) A device used to display computer text and graphics.
Monitor/receiver - A TV having RF tuning circuits to receive broadcast signals for viewing.
Monochrome - One color, usually interpreted as black and white. In computer CRTs, it is any single color with black.
Monochrome composite output - Provides a monochrome video output with combined horizontal and vertical sync for composite video with all the shades of the computer’s monochrome, 8-, 16-, or 64-color display adapter card output signal.
Monochrome signal - A video signal having one color, usually a black and white signal, or sometimes the luma portion of a composite or component color signal.
MPEG - Moving Picture Experts Group. A standards committee under the auspices of the International Standards Organization working on algorithm standards that allow digital compression, storage and transmission of moving image information such as motion video, CD-quality audio, and control data at CD-ROM bandwidth. The MPEG algorithm provides inter-frame compression of video images and can have an effective compression rate of 100:1 to 200:1.
MPEG-2 - The second generation standard for video compression of audio and video applying the discrete cosine transform. The standard includes a combination of lossy video and audio compression methods which permit storage and transmission of movies using currently available storage media and transmission bandwidth. Commonly used for digital television transmission, DVD, and other similar equipment.
MPEG-4 - A patented collection of methods defining compression of audio and visual (AV) digital data. Uses of MPEG-4 include compression of AV data for web (streaming media) and CD distribution, voice (telephone, videophone) and broadcast television applications. MPEG-4 absorbs many of the features of MPEG-1 and MPEG-2 and other related standards, adding new features such as (extended) VRML support for 3D rendering, object-oriented composite files (including audio, video and VRML objects), support for externally-specified Digital Rights Management and various types of interactivity.
MPLS - Multiprotocol Label Switching. A mechanism in high-performance telecommunications networks which directs and carries data from one network node to the next. MPLS makes it easy to create “virtual links” between distant nodes. It can encapsulate packets of various network protocols.
MTBF - Mean Time Between Failures. A basic measure of reliability for repairable items. It can be described as the number of hours that pass before a component, assembly, or system fails. Also (MTBR) Mean Time Between Repairs.
MTP - Extron’s acronym for it’s Mini Twisted Pair line of products.
MTS - Multichannel Television Sound. One of the first stereo sound systems developed for television. MTS consists of two independent singles each carrying a discrete channel. One channel provides stereo sound by providing left/right channel difference signals relative to transmitted mono audio track. The second carrier carries the Secondary Audio Program (SAP) which is used for a second language or for Descriptive Video, a descriptive commentary for the vision impaired.
MTU (Maximum Transfer Unit) - Each network has a maximum transfer unit or MTU, the maximum size for an Ethernet frame payload. Typically the MTU for a network is 1500 bytes. Routers break up data segments into two or more segments if the MTU is smaller than the payload in an Ethernet frame.
Multicast - Multicast addressing is a network technology for the delivery of information to a group of destinations simultaneously using the most efficient strategy to deliver the messages over each link of the network only once, creating copies only when the links to the multiple destinations split. A single stream is sent from the source to a group of recipients.
Multimode Fiber – MMF - An optical fiber that allows for the propagation of more than one mode or light path. It is commonly used with LED light sources for shorter distance links.
Multi-Pass Transform - Multi-pass transforms return to a data set to carry out a process. Multi-pass transforms are often capable of supporting greater compression ratios, but use a greater amount of time to process the data.
Multiple Termination Plug – MTP - A small form factor – SFF plug for multiple fibers.
Multipoint - When more than two locations are connected for a videoconference using a bridge. Usually multipoint switching is done by video-follow-audio, such that the person speaking is automatically seen by the other conference site(s).
Multi-Purpose Transform - A multi-purpose transform is capable of converting more than one type of input format. The PURE3 codec is a multi-purpose transform in respect to its ability to process both video and computer graphic inputs which are different with respect to resolutions, color space, and color information.
Multi-Rate SDI - the capability to support multiple SMPTE serial digital interface standards, including SMPTE 424M (2.97 Gbps 3G-SDI), SMPTE 292M (1.485 Gbps HD-SDI), and SMPTE 259M (270 Mbps SDI).
MUX - Short for multiplexer. A device that combine multiple signals for transmission over a single line. The signals are demultiplexed (DEMUX’d), or separated, at the receiving end.
 

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