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AXIS P3301/AXIS P3304 - Glossary of Terms
Image compression -
Image compression minimizes the file
size (in bytes) of an image. Two of the most common
compressed image formats are JPEG and GIF.
Interlacing -
Interlaced video is video captured at 50
pictures (known as fields) per second, of which every 2
consecutive fields (at half height) are then combined into 1
frame. Interlacing was developed many years ago for the
analog TV world and is still used widely today. It provides
good results when viewing motion in standard TV
pictures, although there is always some degree of
distortion in the image.
To view interlaced video on e.g. a computer monitor, the
video must first be de-interlaced, to produce progressive
video, which consists of complete images, one after the
other, at 25 frames per second. See also
Progressive scan
.
IP (Internet Protocol) -
The Internet Protocol is a method
transmitting data over a network. Data to be sent is divided
into individual and completely independent "packets."
Each computer (or host) on the Internet has at least one
address that uniquely identifies it from all others, and each
data packet contains both the sender's address and the
receiver's address.
The Internet Protocol ensures that the data packets all
arrive at the intended address. As IP is a connectionless
protocol, which means that there is no established
connection between the communication end-points,
packets can be sent via different routes and do not need to
arrive at the destination in the correct order.
Once the data packets have arrived at the correct
destination, another protocol - Transmission Control
Protocol (TCP) - puts them in the right order. See also
TCP
.
IP Address -
An IP address is simply an address on an IP
network used by a computer/device connected to that
network. IP addresses allow all the connected
computers/devices to find each other and to pass data back
and forth.
To avoid conflicts, each IP address on any given network
must be unique. An IP address can be assigned as fixed, so
that it does not change, or it can be assigned dynamically
(and automatically) by DHCP.
An IP address consists of four groups (or quads) of decimal
digits separated by periods, e.g. 130.5.5.25. Different parts
of the address represent different things. Some part will
represent the network number or address, and some other
part will represent the local machine address.
See also
IP (Internet Protocol).
I-VOP -
See
VOP
.
JPEG (Joint Photographic Experts Group) -
Together with
the GIF file format, JPEG is an image file type commonly
used on the web. A JPEG image is a bitmap, and usually
has the file suffix '.jpg' or ".jpeg." When creating a JPEG
image, it is possible to configure the level of compression
to use. As the lowest compression (i.e. the highest quality)
results in the largest file, there is a trade-off between
image quality and file size.
kbit/s (kilobits per second) -
A measure of the bit rate, i.e.
the rate at which bits are passing a given point. See also
Bit rate
.
LAN (Local Area Network) -
A LAN is a group of
computers and associated devices that typically share
common resources within a limited geographical area.
Linux -
Linux is an open source operating system within
the UNIX family. Because of its robustness and availability,
Linux has won popularity in the open source community
and among commercial application developers.
MAC address (Media Access Control address) -
A MAC
address is a unique identifier associated with a piece of
networking equipment, or more specifically, its interface
with the network. For example, the network card in a
computer has its own MAC address.
Manual iris -
This is the opposite to an autoiris, i.e. the
camera iris must be adjusted manually to regulate the
amount of light allowed to reach the image sensor.
Mbit/s (Megabits per second) -
A measure of the bit rate,
i.e. the rate at which bits are passing a given point.
Commonly used to give the ‘speed’ of a network. A LAN
might run at 10 or 100 Mbit/s. See also
Bit rate
.
Monitor -
A monitor is very similar to a standard
television set, but lacks the electronics to pick up regular
television signals.
Motion JPEG -
Motion JPEG is a simple
compression/decompression technique for networked
video. Latency is low and image quality is guaranteed,
regardless of movement or complexity of the image. Image
quality is controlled by adjusting the compression level,
which in turn provides control over the file size, and
thereby the bit rate.
High-quality individual images from the Motion JPEG
stream are easily extracted. See also JPEG.
Megapixel -
See
Pixel
.
MPEG (Moving Picture Experts Group) -
The Moving
Picture Experts Group develops standards for digital video
and audio compression. It operates under the auspices of
the International Organization for Standardization (ISO).
The MPEG standards are an evolving series, each designed
for a different purpose.
MPEG-2 -
MPEG-2 is the designation for a group of audio
and video coding standards, and is typically used to
encode audio and video for broadcast signals, including
digital satellite and Cable TV. MPEG-2, with some
modifications, is also the coding format used by standard
commercial DVD movies.
Multicast -
Bandwidth-conserving technology that reduces
bandwidth usage by simultaneously delivering a single
stream of information to multiple network recipients.
Network connectivity -
The physical (wired or wireless)
and logical (protocol) connection of a computer network or
an individual device to a network, such as the Internet or a
LAN.
NTSC (National Television System Committee) -
NTSC is
the television and video standard in the United States.
NTSC delivers 525 lines at 60 half-frames/second.
