60
AXIS 216FD/FD-V - Glossary of Terms
HTTP (Hypertext Transfer Protocol) -
HTTP is the set of
rules for exchanging files (text, graphic images, sound,
video, and other multimedia files) on the web. The HTTP
protocol runs on top of the TCP/IP suite of protocols.
Hub -
A (network) hub is used to connect multiple devices
to the network. The hub transmits all data to all devices
connected to it, whereas a switch will only transmit the data
to the device it is specifically intended for.
IEEE 802.11 -
A family of standards for wireless LANs. The
802.11 standard supports 1 or 2 Mbit/s transmission on the
2.4 GHz band. IEEE 802.11b specifies an 11 Mbit/s data rate
on the 2.4 GHz band, while 802.11a allows up to 54 Mbit/s
on the 5 GHz band.
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
