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AXIS 241Q/241S - Glossary
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. See also MPEG and Motion JPEG.
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).
Inputs/Outputs (I/Os) - The digital I/Os on, for example, a network camera can be used to connect any device that can toggle
between an open and a closed circuit.
For example, if a door switch is used as an input device, opening the door could trigger the upload of video images and the
sending of notification messages.
An output might, for example, be used to automatically start a siren when there is a motion detection trigger.
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.
Lux - A standard unit of illumination measurement.
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 of an auto iris, 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 television set, but lacks the electronics to pick up regular television signals.