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Video Terms Explained
Main Table of Contents
A Video Terms
B Video Terms
C Video Terms
D Video Terms
E Video Terms
F Video Terms
G Video Terms
H Video Terms
I Video Terms
J Video Terms
K Video Terms
L Video Terms
M Video Terms
N Video Terms
O Video Terms
P Video Terms
Q Video Terms
R Video Terms
S Video Terms
T Video Terms
U Video Terms
V Video Terms
W Video Terms
X Video Terms
Y Video Terms
Z Video Terms

A Terms

A/B Roll: An edit which involves two source machines and a record machine. A/B rolls are used when dissolves and other effects between two sources are required. The edit controller manages the control of the two source devices (A and B decks), an SEG (Special Effects Generator) or other device which performs the effect, and the record deck. The effect occurs when the A and B decks are both rolling, and the SEG makes a transition (such as a dissolve, wipe, etc.) from one deck to the other.

A/D, A to D: Analog to digital. The conversion of an analog signal into its digital equivalent. A conversion process that changes an analog signal into a digital signal. It is achieved by sampling the signal at intervals and then quantifying each sample to give them values suitable for use in a digital system.

AC: The method of power transmission used throughout most of the world. The primary characteristic of alternating current is a continuously variable voltage that changes in polarity (positive to negative) at a repeating interval. In the U.S., these changes occur at a rate of 60 cycles per second or 60 Hertz (Hz). AC power standards are strictly regulated in each country and are often used as a point of reference for signal timing and synchronization in electronic circuitry.

AC-3: Dolby audio compression system.

Access Time: The total time required to find, retrieve, and display information. Access time varies from minutes on a videotape, seconds on videodisc and CD-ROM, to milli-seconds on a computer.

Access: The action of retrieving a specific segment on a videodisc, VCR, or other source device.

Acquisition: The process of acquiring video footage. Usually refers to acquiring footage on one format with the intention of performing post-production work from the acquisition format to a higher-quality format.

Adaptive Multichannel Prediction: A method of audio, multichannel data reduction exploiting statistical inter-channel dependencies.

Adaptive Segmentation: A subdivision of the digital representation of an audio signal in variable segments of time.

Additive Color System: A color system in which an image is reproduced by mixing appropriate amounts of red, green, and blue lights.

Address: The location on the videotape by time code frame number.

ADSL: Asymmetrical Digital Subscriber Line. A technology that allows video to be sent over the phone companies' twisted pair copper wire to the home. Depending on a customer's distance from the central office, data rates of 1.5, 3 or 6Mbps can be achieved. Supports a low data rate return channel and concurrent unimpaired phone use while receiving video.

AGC (Automatic Gain Control): Circuitry that automatically adjusts the gain level providing optimum signal output and preventing potentially damaging circuit overload. AGC circuits are used in cameras and recording devices, and other video devices to maintain proper signal levels without requiring an operator to manually monitor controls. (See Gain).

Akebono: Digital information recorder, Digital Tape Format (DTF). Sony model numbers GY-10D (drive) and GY-10C (controller).

ALC (Automatic Level Control): Similar to AGC, the ALC circuit automatically adjusts the voltage level on camera pick-up tubes to compensate for fluctuations in the level of light on the tube surface.

Algorithm: A mathematical representation of a procedure used to solve a problem.

Alias: Inaccurate rendering of an image due to a low, digital-sampling rate. Aliasing appears as jaggies, or jagged edges on graphics and especially text. Aliasing is corrected by special software and techniques (anti-aliasing) which smooth out the jagged edges by anticipating and displaying the interim pixels. In analog CCD systems, a form of distortion that is associated with the process of signal sampling, resulting in stair-step edges on diagonal lines within the image.

ALTS: Alternate Local Transport Services. (Also see CAP)

Ambient: Surrounding on all sides; environment. Ambient or overall light is directed around rather than at the subject. Ambient noise is background or existing sounds at a location. Ambient air is the sound of a movie set or other location at its normal quiet level, as distinct from absolute silence.

Ambient Light: The normal unaltered lighting conditions of a scene. Ambient would include normal room illumination (indoors) or normal conditions outdoors.

Amplifier: Device which performs amplification. It increases with current, voltage and/or power of the input signal.

Amplitude: How large or powerful the signal is, determined by the quantitative value of the signal.

Analog: The representation of one continuously variable physical quality such as voltage, current, etc. which varies as a function of another variable such as time.

Analog Recording: The recording of a continuously variable electronic signal. Analog recording is the basis for all conventional (non-digital) audio and video recording techniques. The recorded signal is a duplicate representation of (analogous to) the original signal. Analog recording's major drawback is the introduction of inherent electronic noise to the recorded signal which increases each time the signal is processed or re-recorded.

Analog to Digital Conversion, A/D: The process of converting an analog signal into a digital bit stream. Includes the steps of sampling and quantizing.

Analog to Digital Converter: An electronic circuit that changes continuously variable analog signals into discrete numerical digital signals (bits). The common abbreviation is A/D.

Angle of View: That portion of a scene visible through a particular lens. Angle of view is determined by the lens focal length. Wide angle lenses have a greater angle of view and, therefore, show a wider area of the subject. Telephoto lenses have a narrow angle of view showing smaller portions or close-ups of the subject.

ANI: Automatic Number Identification. Calls from wired phones in equal access local exchanges are preceded by the phone number that placed the call. This enables caller ID. In equal access local telephone exchanges, the phone numbers of the originating caller is automatically signaled to the destination (call terminating) local switch.

Anaimatics: That portion of a scene visible through a particular lens. Angle of view is determined by the lens focal length. Wide angle lenses have a greater angle of view and, therefore, show a wider area of the subject. Telephoto lenses have a narrow angle of view showing smaller portions or close-ups of the subject.

Animation: Single images displayed in rapid sequence producing the illusion of motion.

ANSI: American National Standards Institute

Antenna: A device for radiating or receiving radio waves.

Anti-Aliasing: Aliasing causes jagged edges in images displayed on a computer screen in low resolution. Anti-aliasing software smoothes the stair-step effect by anticipating and displaying the interim pixels. In analog CCD systems, anti-aliasing is accomplished by the removal of unwanted high-frequency components through the means of a high-frequency-cut optical filter placed before the imager.

Aperture: The iris opening in a lens that regulates the amount of light passing into the camera. The size of the aperture opening determines the amount of light that will get to the imager. The larger the opening, the more light that enters. Aperture is usually signified in f/stops.

Application Controller: Computer system that runs the application software for LMSª and provides operator-machine interface. The LMS uses a Motorola 68030 microprocessor to run the computer system and uses UNIX (trademark of AT&T Corp.) as its operation system. The application controller may run the LMS independently or be controlled by a larger mainframe via a host computer interface. (See Host Computer).

Artifacts: Unpleasant visual problems within the signal such as noise, chroma displacement, etc.

ASCII: American Standard Code for Information Interchange. A 128 character set that includes the upper case and lower case English alphabet, numerals, special symbols, and 32 control codes. Each character is represented by a 7-bit binary number. Therefore, one ASCII-encoded character can be stored in one byte of computer memory.

As-Run Log: A record of the tape replay activity on an LMSª system kept by the application software. The as run log is maintained to log on-aired material records for operational and billing purposes, as well as to record some error messages for maintenance purposes.

Aspect Ratio: The ratio of height over width of an image: a standard video monitor has an aspect ratio of three units of height (vertical) to four units of width (horizontal). This is expressed as a 3:4 aspect ratio. Images will become distorted if forced into a different aspect ratio during enlargement, reductions, or transfers. The aspect ratio for HDTV is 9:16.

Assemble Editing: A method of electronic editing in which various taped segments are re-taped in a determined sequence to produce a coherent whole. Assemble editing is used to join together larger, pre-edited segments rather than to edit complex, professionally-produced programs.

Asynchronous: Having a variable time interval between successive bits, characters, or events. Each character is individually arranged, usually by using start and stop bits.

Asynchronous Communication: Data transmission where the time interval between characters is allowed to vary.

ATM: Asynchronous Transfer Mode. ATM is a packet based transmission system that can accommodate any type of encoded digital data (including video, voice, or computer data). Packets can be switched for transmission to any location because of the packets feature of self addressing.

ATR : (1) This is the replacement of a customer's Sony product with a new one of equal value. This occurs when the unit can not be repaired by the RSC, or can not be repaired in the RSC, for reasons of expediency, or all "Tokuren" product. The Sony sales organization responsible for selling the product must initiate the ATR paperwork.

(2) Audio Tape Recorder.

(3) for a processing device to respond to an input signal.

Attenuation: A decrease in the magnitude of a signal. It may be expressed as a ratio, or in decibels. The opposite of amplification.

ATV: Advanced Television. Transmission system for delivery of ATV signals to the home.

Audio Dub: (1.) To re-record the audio portion of a videotape without disturbing the video portion of the signal. (2.) To make a copy of an audio tape.

Audio Subsystem: Audio component of a videoconferencing system. The most sophisticated audio subsystems today are full-duplex and employ echo canceller technology. Full duplex allows both sides of a videoconference to hear each other simultaneously without one side being cut off while the other speaks. This provides a more natural and productive environment than less sophisticated subsystems. Echo cancellers insure that audio sent to a remote room is not re-broadcast back to the sender creating an annoying echo effect.

Authoring System: Specialized computer software which allows users to design interactive courseware in everyday language without the painstaking detail of computer programming.

Auto-Iris: A lens iris equipped with a photosensitive detector that can read changes in lighting conditions and automatically open or close the iris to compensate for the changes.

Auxiliary Bus: Also called "Aux" buses, auxiliary buses are extra switching buses that allow video signals connected to the switcher to be routed to external equipment such as digital effects systems and VTRs. Some switchers such as the DVS-2000C have multiple Aux buses as an option.

Axis: A line that is fixed, along which distances are measured or to which positions are referenced.