Glossary of Video Terms and Acronyms - Isotest

Video Terms and Acronyms
Glossary
Coating Resistance – The electrical resistance of the coating measured
between two parallel electrodes spaced a known distance apart along the
length of tape.
Coating Thickness – The thickness of the magnetic coating applied to
the base film of a mag tape. Modern tape coatings range in thickness from
170 to 650 microinches. Coating thickness is normally optimized for the
intended application. In general, thin coatings give good resolution at the
expense of reduced output at long wavelengths; thick coatings give a high
output at long wavelengths at the expense of degraded resolution.
Coaxial Cable – a) A transmission line with a concentric pair of signal
carrying conductors. There is an inner conductor and an outer conductor
metallic sheath. The sheath aids in preventing external radiation from
affecting the signal on the inner conductor and minimizes signal radiation
from the transmission line. b) A large cable composed of fine foil wires
that is used to carry high bandwidth signals such as cable TV or cable
modem data streams.
Cobalt Doped Oxide – A type of coating used on magnetic recording
tape. This is normally a gamma ferric oxide particle which has been doped
with cobalt to achieve a higher coercivity. Modern forms of this oxide are
acicular and have been used to make tapes with coercivities in excess of
1000 oersteds.
Co-Channel Interference – Interference caused by two or more television
broadcast stations using the same transmission channel in different cities.
It is a form of interference that affects only broadcast television.
Code – a) In computers, the machine language itself, or the process of
converting from one language to another. b) A plan for representing each
of a finite number of values or symbols as a particular arrangement or
sequence of discrete conditions or events. To encode is to express given
information by means of a code. c) A system of rules defining a one-to-one
correspondence between information and its representation by characters,
symbols, or signal elements.
CODEC (Coding/Decoding) – a) The algorithm used to capture analog
video or audio onto your hard drive. b) Used to implement the physical
combination of the coding and decoding circuits. c) A device for converting
signals from analog to coded digital and then back again for use in digital
transmission schemes. Most codecs employ proprietary coding algorithms
for data compression. See Coder-Decoder.
Coded Order – The order in which the pictures are stored and decoded.
This order is not necessarily the same as the display order.
Coded Orthogonal Frequency-Division Multiplex – A modified form of
OFDM. A modulation scheme used for digital transmission that is employed
by the European DVB system. It uses a very large number of carriers (hundreds
or thousands), each carrying data at a very low rate. The system is
relatively insensitive to doppler frequency shifts, and can use multipath signals
constructively. It is, therefore, particularly suited for mobile reception
and for single-frequency networks.
Coded Representation – A data element as represented in its encoded
form.
Code-Excited Linear Prediction – Audio encoding method for low-bit
rate codecs.
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Coder-Decoder – Used to implement the physical combination of the coding
and decoding circuits.
Coding – Representing each level of a video or audio signal as a number,
usually in binary form.
Coding Parameters – The set of user-definable parameters that characterize
a coded video bit stream. Bit streams are characterized by coding
parameters. Decoders are characterized by the bit streams that they are
capable of decoding.
Coefficient – a) A number (often a constant) that expresses some property
of a physical system in a quantitative way. b) A number specifying the
amplitude of a particular frequency in a transform.
Coefficient of Friction – The tangential force required to maintain
(dynamic coefficient) or initiate (static coefficient) motion between two surfaces
divided by the normal force pressing the two surfaces together.
Coefficient of Hygroscopic Expansion – The relative increase in the linear
dimension of a tape or base material per percent increase in relative
humidity measured in a given humidity range.
Coefficient of Thermal Expansion – The relative increase in the linear
dimension of a tape or base material per degree rise in temperature (usually
Fahrenheit) measured in a given temperature range.
Coercivity – Measured in oersteds, the measurement of a magnetic characteristic.
The demagnetizing force required to reduce the magnetic induction
in a magnetic materiel to zero from its saturated condition.
COFDM (Coded Orthogonal Frequency Domain Multiplex) – Up to
6875 single carriers 1 kHz apart are QAM modulated with up to 64 states.
“Coded” means that the data to be modulated has error control.
Orthogonality means that the spectra of the individual carriers do not influence
each other as a spectral maximum always coincides with a spectrum
zero of the adjacent carriers. A single-frequency network is used for the
actual transmission.
Collision – The result of two devices trying to use a shared transmission
medium simultaneously. The interference ruins both signals, requiring both
devices to retransmit the data lost due to collision.
Color Back Porch – Refer to the Horizontal Timing discussion.
Color Background Generator – a) A circuit that generates a full-field
solid color for use as a background in a video picture. b) A device that produces
a full-frame color, normally used as a background for various graphics
effects, the output of which is selectable on the last button of all
switcher buses.
Color Balance – Adjustment of color in the camera to meet a desired
standard, i.e., color bar, sponsor’s product, flesh tones. Also may be
referred to as “white balance.”
Color Bar Test Signal – Originally designed to test early color camera
encoders, it is commonly (albeit incorrectly) used as a standard test signal.
The saturated color bars and luminance gray bar are usually used to check
monitors for color accuracy. The saturated color bars are a poor test of any
nonlinear circuit or system and at best, show video continuity. Testing a
video system using color bars is analogous to testing an audio system
using a simple set of monotonal frequencies. Many color TV test signals