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AXIS Q1755 - Glossary of Terms

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

pic

tures (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

vide

o 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

destina

tion, 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

netw

ork 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 b

e 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 separa

ted 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 (Inte

rnet Protocol).

I-VOP - See VOP.

JPEG (Joint Photographic Experts Group) - Together with

the G

IF 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

omputers 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

addre

ss 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

cam

era 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

tele

vision set, but lacks the electronics to pick up regular

television signals.

Motion JPEG - Motion JPEG is a simple

com

pression/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 ea

sily extracted. See also JPEG.

Megapixel - See Pi

xel.

MPEG (Moving Picture Experts Group) - The Moving

Picture Expe

rts 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.

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

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