Datasheet

26
AXIS 292 - Glossary of Terms
background).
As color cameras can "see" infrared radiation as well as visible light, these
came
ras are equipped with an IR-cut filter, to prevent distortion of the
colors the human eye can see. To use the camera in very dark locations or
at night, this filter can be removed, to allow infrared radiation to hit the
image sensor and thus produce images.
An infrared lamp can be used for improved illumination for night
s
urveillance, whilst not producing any extra visible light.
I-VOP - See VOP.
JPEG (Joint Photographi
c 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
a
ssociated 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.
Lux - A standard unit of illumination measurement.
MAC address (Media Access Control address) - A MAC address is a
uniq
ue 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 netw
orked 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
extracte
d. See also JPEG.
Megapixel - See pi
xel.
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.
MPEG-4 - MPEG-4 is a group of audio and video coding standards and
r
elated technology. The primary uses for the MPEG-4 standard are web
(streaming media) and CD distribution, conversational (videophone), and
broadcast television.
Most of the features included in MPEG-
4 are left to individual developers
to decide whether to implement them or not. This means that there are
probably no complete implementations of the entire MPEG-4 set of
standards. To deal with this, the standard includes the concept of
"profiles" and "levels", allowing a specific set of capabilities to be defined
in a manner appropriate for a subset of applications.
Multicast - Bandwidth-conserving technology that reduces bandwidth
usage by simultaneously delive
ring a single stream of information to
multiple network recipients.
Multiplexer - A multiplexer is a high-speed switch that provides
full-screen
images from up to 16 analog cameras. Multiplexers can
playback everything that happened on any one camera with no
interference from the other cameras on the system.
Network connectivity - The physical (wired or wireless) and logical
(protoc
ol) connection of a computer network or an individual device to a
network, such as the Internet or a LAN.
NTSC (National Television System Com
mittee) - NTSC is the television
and video standard in the United States. NTSC delivers 525 lines at 60
half-frames/second.
OEM (Original Equipment Manufacturer) - This is a designation for
c
ompanies that manufacture equipment which is then marketed and sold
to other companies under their own names.
PAL (Phase Alternating Line) - PAL is the dominant television standard
in Europe
. PAL delivers 625 lines at 50 half-frames/second.
PEM (Privacy Enhanced Mail) - An early standard for securing
ele
ctronic mail. The PEM-format is often used for representing an HTTPS
certificate or certificate request.
Ping - Ping is a basic network program used diagnostically to check the
status of a
network host or device. Ping can be used to see if a particular
network address (IP address or host name) is occupied or not, or if the
host at that address is responding normally. Ping can be run from e.g. the
Windows Command prompt or the command line in Unix.
Pixel - A pixel is one of the many tiny dots that make up a digital image.
The color and inten
sity of each pixel represents a tiny area of the
complete image.
PoE (Power over Ethernet) - Power over Ethernet provides power to a
netw
ork device via the same cable as used for the network connection.
This is very useful for IP-Surveillance and remote monitoring applications
in places where it may be too impractical or expensive to power the
device from a power outlet.
PPP (Point-to-Point Protocol) - A protocol that uses a serial interface for
co
mmunication between two network devices. For example, a PC
connected by a phone line to a server.
PPTP (Point-to-Point Tunnelling Protocol) - A protocol (set of
co
mmunication rules) that allows corporations to extend their own
corporate network through private "tunnels" over the public Internet. In
this way a corporation can effectively use a WAN (Wide Area Network) as
a large single LAN (Local Area Network). This kind of interconnection is
known as a virtual private network (VPN).
Pre/post alarm images - The images from immediately before and after
an alarm
. These images are stored in a buffer for later retrieval.
Progressive scan - Progressive scan, as opposed to interlaced video, scans
the entire
picture, line by line every sixteenth of a second. In other words,
captured images are not split into separate fields as in interlaced
scanning.
Computer monitors do not need interlace to show the picture on the
scree
n, but instead show them progressively, on one line at a time in
perfect order, i.e. 1, 2, 3, 4, 5, 6, 7 etc., so there is virtually no "flickering"
effect. In a surveillance application, this can be critical when viewing
detail within a moving image, such as a person running. A high-quality
monitor is required to get the best from progressive scan. See also
interlacing.
Protocol - A special set of rules governing how two entities will
co
mmunicate. Protocols are found at many levels of communication, and
there are hardware protocols and software protocols.
Proxy server - In an organization that uses the Internet, a proxy server
ac
ts as an intermediary between a workstation user and the Internet. This
provides security, administrative control, and a caching service. Any
proxy server associated with a gateway server, or part of a gateway
server, effectively separates the enterprise network from the outside
network and the local firewall. It is the firewall server that protects the
enterprise network from outside intrusion.