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AXIS COMMUNICATIONS
<Product Name> Quick User’s Guide
AXIS 211M - Glossary of Terms
45
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.
MPEG-4 - MPEG-4 is a group of audio and video coding standards and
related 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 delivering 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
(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.
OEM (Original Equipment Manufacturer) - This is a designation for
companies 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
electronic 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 intensity of each pixel represents a tiny area of the
complete image.
PoE (Power over Ethernet) - Power over Ethernet provides power to a
network 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 communication between two network devices. For example, a PC
connected by a phone line to a server.
PPTP (Point-to-Point tunneling Protocol) - A protocol (set of
communication 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
screen, 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
communicate. 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
acts 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 organization’s network from the outside
network and the local firewall. It is the firewall server that protects the
network against outside intrusion.
A proxy server receives requests for Internet services (such as web page
requests) from many users. If the proxy server is also a cache server, it
looks in its local cache of previously downloaded web pages. If it finds
the page, it is returned to the user without forwarding the request to the
Internet. If the page is not in the cache, the proxy server, acting as a
client on behalf of the user, uses one of its own IP addresses to request
the page from another server over the Internet. When the requested page
is returned, the proxy server forwards it to the user that originally
requested it.
P-VOP - See VOP.
Quality of Service (QoS) - QoS provides the means to guarantee a certain
level of a specified resource to selected traffic on a network. Quality can
be defined as, e.g. a maintained level of bandwidth, low latency, no
packet losses, etc.
Resolution - Image resolution is a measure of how much detail a digital
image can hold: the greater the resolution, the greater the level of detail.
Resolution can be specified as the number of pixel-columns (width) by
the number of pixel-rows (height), e.g. 320x240.