Glossary of Video Terms and Acronyms - Isotest

Video Terms and Acronyms
Glossary
edit point. Inserting a new control track allows for a constant speed reference
throughout the entire tape.
Assembler Program – Translates assembly language statements
(mnemonics) into machine language.
Assembly Language – Machine-oriented language. A program is normally
written as a series of statements using mnemonic symbols that suggest
the definition of the instruction. It is then translated into machine language
by an assembler program.
ASVP – Application-Specific Virtual Prototype.
Asymmetric Compression – Compression in which the encoding and
decoding require different processing power (the encoding is normally
more demanding).
Asymmetrical Digital Subscriber Line – Bellcore’s term for one-way
T-1 to the home over the plain old, single twisted pair wiring already going
to homes. ADSL is designed to carry video to the home. ADSL, like ISDN,
uses adaptive digital filtering, which is a way of adjusting itself to overcome
noise and other problems on the line. According to Northern Telecom,
initial ADSL field trails and business cases have focused on ADSL’s potential
for video-on-demand service, in competition with cable pay-per-view
and neighborhood video rental stores. But ADSL offers a wide range of
other applications, including education and health care. Once telephone
companies are able to deliver megabits to the home, Northern Telecom
expects an explosion in potential applications including work-at-home
access to corporate LANs, interactive services such as home shopping and
home banking and even multi-party video gaming, interactive travelogues,
and remote medical diagnosis. Multimedia retrieval will also become possible,
enabling the home user to browse through libraries of text, audio, and
image data – or simply subscribe to CD-quality music services. In the field
of education, ADSL could make it possible to provide a low-cost “scholar’s
workstation” – little more than a keyboard, mouse and screen – to every
student, providing access to unlimited computer processing resources from
their home. For a more modern version of ADSL, see DMT, which stands for
Discrete Multi-Tone.
Asynchronous – a) A transmission procedure that is not synchronized by
a clock. b) Any circuit or system that is not synchronized by a common
clock signal.
Asynchronous Data Streaming – Streaming of data only without any
timing requirements. See Asynchronous Data Streaming, Synchronous Data
Streaming.
Asynchronous Transfer Mode (ATM) – a) A digital transmission system
using packets of 53 bytes for transmission. ATM may be used for LANs and
WANs. ATM is a switching/transmission technique where data is transmitted
in small, 53-byte fixed sized cells (5-byte header, 48-byte payload). The
cells lend themselves both to the time-division-multiplexing characteristics
of the transmission media, and the packet switching characteristics desired
of data networks. At each switching node, the ATM header identifies a virtual
path or virtual circuit that the cell contains data for, enabling the
switch to forward the cell to the correct next-hop trunk. The virtual path is
set up through the involved switches when two endpoints wish to communicate.
This type of switching can be implemented in hardware, almost
essential when trunk speeds range from 45 Mb/s to 1 Gb/s. The ATM
12 www.tektronix.com/video_audio
Forum, a worldwide organization, aimed at promoting ATM within the
industry and the end-user community was formed in October 1991 and
currently includes more than 500 companies representing all sectors of the
communications and computer industries, as well as a number of government
agencies, research organizations, and users. b) A digital signal protocol
for efficient transport of both constant-rate and bursty information in
broadband digital networks.
AT&T – Consumer electronics manufacturer and long-distance telephone,
television, and data carrier. Its Bell Labs has worked on the development of
ATV systems.
ATC – Adaptive Transform Coding.
ATC (American Television and Communications) – Time Inc.’s CATV
multiple-system operator (MSO), a co-proposer with HBO of C-HDTV and a
supporter of ACTV.
ATEL – Advanced Television Evaluation Laboratory)
A-Time (Absolute Time) – Elapsed time, referenced to the program start
(00:00:00), on a DVD. A-time is measured in minutes, seconds, and
frames.
ATM – See Asynchronous Transfer Mode.
A-to-D Converter (ADC) – a) A circuit that uses digital sampling to convert
an analog signal into a digital representation of that signal. An ADC for
digitizing video must be capable of sampling at 10 to 150 million samples
per second (MSPS). b) Converts analog voltages and currents to the digital
representation used by computer systems. This enables the computer to
sense real-world signals.
ATRAC (Adaptive Transform Acoustic Coding) – An algorithm that
splits an audio signal into three non-uniform sub-bands.
ATRP – Advanced Television Research Program.
ATSC – See Advanced Television Systems Committee.
Attack – In audio terms, the beginning of a sound. What type of attack a
sound has is determined by how long it takes for the volume of the sound
to go from silence to maximum level. It is critical to consider the attack
time of sounds when applying processing Compression, gating, and other
types of processors as they may destroy a sound’s attack, changing the
character and quality of the audio. Reverbs can also be affected by attack
time; careful use of a reverb’s predelay parameter will allow you to optimize
the reverb for different types of attacks.
ATTC (Advanced Television Test Center) – Created by seven broadcasting
organizations to test different broadcast ATV systems. See also Cable Labs.
ATT-C (AT&T Communications) – The Long distance arm of AT&T.
Attenuation – A decrease in the level of a signal is referred to as attenuation.
In some cases, this is unintentional, as in the attenuation caused by
using wire for signal transmission. Attenuators (circuits which attenuate a
signal) may also be used to lower the level of a signal in an audio system
to prevent overload and distortion.
ATV – See Advanced TV.
AU – See Access Unit.