Glossary of Video Terms and Acronyms - Isotest

Video Terms and Acronyms
Glossary
DD2 – Data recorders that have been developed using D2 tape offer relatively
vast storage of image or other data. Various data transfer rates are
available for different computer interfaces. Other computer storage media
editing is difficult and images are not directly viewable.
DDB – Download Data Block.
DDC – Data Download Control.
DDC2B – A serial control interface standard used to operate control registers
in picture monitors and video chips. The two-wire system is defined by
data and clock signals.
DDP (Disc Description Protocol) – A file or group of files which describe
how to master a data image file for optical disc (DVD or CD). This is an
ANSI industry standard developed by Doug Carson and Associates. The
laser beam recorders use this information in the mastering process.
DDR (Digital Disk Recorder) – See Digital Disk Recorder.
DDS – Digital Data Service.
Debouncing – Elimination of the bounce signals characteristic of mechanical
switches. Debouncing can be performed by either hardware or
software.
Debugger – A program designed to facilitate software debugging. In general,
it provides breakpoints, dump facilities, and the ability to examine and
modify registers and memory.
Decay – a) The length of time it takes for an audio signal to fall below the
noise threshold. b) The adjustable length of time it takes for an ADO
DigiTrail effect to complete. (The trail catches up with the primary video.)
Decay Time – The time it takes for a signal to decrease to one-millionth
of its original value (60 dB down from its original level).
Decibel – One-tenth of a Bel. It is a relative measure of signal or sound
intensity or “volume.” It expresses the ratio of one intensity to another. One
dB is about the smallest change in sound volume that the human ear can
detect. (Can also express voltage and power ratios logarithmically.) Used to
define the ratio of two powers, voltages, or currents. See the definitions of
dB, dBm, and dBw.
Decimation – Term used to describe the process by which an image file is
reduced by throwing away sampled points. If an image array consisted of
100 samples on the X axis and 100 samples on the Y axis, and every other
sample where thrown away, the image file is decimated by a factor of 2
and the size of the file is reduced by 1/4. If only one sample out of every
four is saved, the decimation factor is 4 and the file size is 1/16 of the
original. Decimation is a low-cost way of compressing video files and is
found in many low-cost systems. Decimation however introduces many
artifacts that are unacceptable in higher-cost systems.
Decimation Filter – The Decimation Filter is designed to provide decimation
without the severe artifacts associated with throwing data away
although artifacts still exist. (See the definition of Decimation.) The
Decimation Filter process still throws data away but reduces image artifacts
by smoothing out the voltage steps between sampled points.
Deck, Tape – A tape recorder that does not include power amplifiers or
speakers.
Decode – To separate a composite video signal into its component parts.
46 www.tektronix.com/video_audio
Decoded Stream – The decoded reconstruction of a compressed bit
stream.
Decoder – a) Device used to recover the component signals from a composite
(encoded) source. Decoders are used in displays and in various processing
hardware where component signals are required from a composite
source such as composite chroma keying or color correction equipment.
b) Device that changes NTSC signals into component signals; sometimes
devices that change digital signals to analog (see DAC). All color TV sets
must include an NTSC decoder. Because sets are so inexpensive, such
decoders are often quite rudimentary. c) An embodiment of a decoding
process.
Decoder Input Buffer – The first-in first-out (FIFO) buffer specified in the
video buffering verifier.
Decoder Input Rate – The data rate specified in the video buffering verifier
and encoded in the coded video bit stream.
Decoding (Process) – The process that reads an input coded bit stream
and produces decoded pictures or audio samples.
Decoding Time Stamp (DTS) – A field that may be present in a PES
packet header that indicates the time that an access unit is decoded in the
system target decoder.
Decompress – The process of converting video and audio data from its
compact form back into its original form in order to play it. Compare
Compress.
Decrement – Programming instruction that decreases the contents of a
storage location.
DECT – Digital Enhanced Cordless Telecommunications.
Dedicated – Set apart for some special use. A dedicated microprocessor
is one that has been specially programmed for a single application such as
weight measurement, traffic light control, etc. ROMs, by their very nature,
are dedicated memories.
Dedicated Keyboard – A keyboard assigned to a specific purpose.
Deemphasis – Also known as postemphasis and post-equalization.
Deemphasis modifies the frequency-response characteristic of the signal in
a way that is complementary to that introduced by preemphasis.
Deemphasis Network – Circuit that restores the preemphasized frequency
response to its original levels.
Deesser – A compressor which reduces sibilance by triggering compression
when it senses the presence of high frequency signals above the compression
threshold.
Default – The setup condition (for example, transition rate settings, color
of the matte gens, push-button status) existing when a device is first
powered-up, before you make any changes.
Default Printer – The printer to which the system directs a print request if
you do not specify a printer when you make the request. You set the
default printer using the Print Manager.
Defaults – A set of behaviors specified on every system. You can later
change these specifications which range from how your screen looks to
what type of drive you want to use to install new software.