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AXIS M1011/M1011-W/M1031-W - Glossary of Terms
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 - A video compression standard that makes good
use o
f bandwidth, and which can provide DVD-quality
video streams at less than 1 Mbit/s.
Multicast - Bandwidth-conserving technology that reduces
band
width usage by simultaneously delivering a single
stream of information to multiple network recipients.
Network connectivity - The physical (wired or wireless)
and lo
gical (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.
NWay - A network protocol that automatically negotiates
the highest possible com
mon transmission speed between
two devices.
PAL (Phase Alternating Line) - PAL is the dominant
tele
vision standard in Europe. PAL delivers 625 lines at 50
half-frames/second.
Ping - Ping is a basic network program used
diag
nostically 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.
PIR - A Passive InfraRed sensor (PIR Sensor) is an
ele
ctronic device that measures infrared (IR) light radiating
from objects in its field of view. They are generally used as
motion detectors. Motion is detected when an infrared
object such as person that has one temperature passes in
front of another object that has a different temperature
such as wall.
Pixel - A pixel is one of the many tiny dots that make up a
digita
l image. The color and intensity of each pixel
represents a tiny area of the complete image.
PoE (Power over Ethernet) - Power over Ethernet provides
pow
er 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
bef
ore and after an alarm. These images are stored in a
buffer for later retrieval.
Progressive scan - Progressive scan, as opposed to
interla
ced 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 com
municate. 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 serve
r 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 we
b 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.
Resolution - Image resolution is a measure of how much
deta
il 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.
Alternatively, the total number of pixels (usually in
meg
apixels) in the image can be used. In analog systems it
is also common to use other format designations, such as
CIF, QCIF, 4CIF, etc.
RTCP (Real-Time Cont
rol Protocol) - RTCP provides
support for real-time conferencing of groups of any size
within an intranet. This support includes source
identification and support for gateways like audio and