User`s manual

65
AXIS 216FD/FD-V/MFD/MFD-V - Glossary of Terms
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
ind
ividual 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
ba
ndwidth usage by simultaneously delivering a single
stream of information to multiple network recipients.
Network connectivity - The physical (wired or wireless)
an
d 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 tele
vision and video standard in the United States. NTSC
delivers 525 lines at 60 half-frames/second.
PAL (Phase Alterna
ting Line) - PAL is the dominant
television standard in Europe. PAL delivers 625 lines at 50
half-frames/second.
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
dig
ital image. The color and intensity of each pixel
represents a tiny area of the complete image.
PoE (Power over Ethernet) - Power over Ethernet provides
po
wer 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
seria
l 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
be
fore and after an alarm. These images are stored in a
buffer for later retrieval.
Progressive scan - Progressive scan, as opposed to
interlace
d 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 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
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.
Resolution - Image resolution is a measure of how much
detail a digital imag
e 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
megap
ixels) 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 Control Protocol) - RTCP provides
s
upport for real-time conferencing of groups of any size
within an intranet. This support includes source
identification and support for gateways like audio and video
bridges as well as multicast-to-unicast translators.
RTCP offers quality-of-service feedback from receivers to
the
multicast group as well as support for the
synchronization of different media streams.