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AXIS COMMUNICATIONS
<Product Name> Quick User’s Guide
AXIS 211M - Glossary of Terms
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Alternatively, the total number of pixels (usually in megapixels) 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 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 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.
RTP (Real-Time Transport Protocol) - RTP is an Internet protocol for
the transport of real-time data, e.g. audio and video. It can be used for
media-on-demand as well as interactive services such as Internet
telephony.
RTSP (Real Time Streaming Protocol) - RTSP is a control protocol, and
a starting point for negotiating transports such as RTP, multicast and
Unicast, and for negotiating codecs.
RTSP can be considered a "remote control" for controlling the media
stream delivered by a media server. RTSP servers typically use RTP as
the protocol for the actual transport of audio/video data.
Router - A device that determines the next network point to which a
packet should be forwarded on its way to its final destination. A router
creates and/or maintains a special routing table that stores information
on how best to reach certain destinations. A router is sometimes
included as part of a network switch. See also switch.
Server - In general, a server is a computer program that provides
services to other computer programs in the same or other computers. A
computer running a server program is also frequently referred to as a
server. In practice, the server may contain any number of server and
client programs. A web server is the computer program that supplies the
requested HTML pages or files to the client (browser).
Sharpness - This is the control of fine detail within a picture. This
feature was originally introduced into color TV sets that used notch filter
decoders. This filter took away all high frequency detail in the black and
white region of the picture. The sharpness control attempted to put some
of that detail back in the picture. Sharpness controls are mostly
superfluous in today's high-end TVs. The only logical requirement for it
nowadays is on a VHS machine.
Simplex - In Simplex operation, a network cable or communications
channel can only send information in one direction.
SMTP (Simple Mail Transfer Protocol) - SMTP is used for sending and
receiving e-mail. However, as it is "simple," it is limited in its ability to
queue messages at the receiving end, and is usually used with one of two
other protocols, POP3 or IMAP. These other protocols allow the user to
save messages in a server mailbox and download them periodically from
the server.
SMTP authentication is an extension of SMTP, whereby the client is
required to log into the mail server before or during the sending of
email. It can be used to allow legitimate users to send email while
denying the service to unauthorized users, such as spammers.
SNMP (Simple Network Management Protocol) - SNMP forms part of
the Internet Protocol suite, as defined by the Internet Engineering Task
Force. The protocol can support monitoring of network-attached devices
for any conditions that warrant administrative attention.
Sockets - Sockets are a method for communication between a client
program and a server program over a network. A socket is defined as
"the endpoint in a connection." Sockets are created and used with a set
of programming requests or "function calls" sometimes called the
sockets application programming interface (API).
SSL/TLS (Secure Socket Layer/Transport Layer Security)
These two protocols (SSL is succeeded by TLS) are cryptographic
protocols that provide secure communication on a network. SSL is
commonly used over HTTP to form HTTPS, as used, e.g. on the Internet
for electronic financial transactions. SSL uses public key certificates to
verify the identity of the server.
Subnet/subnet mask - A subnet is an identifiably separate part of an
organization's network. Typically, a subnet may represent all the
machines at one geographic location, in one building, or on the same
local area network (LAN). Having an organization's network divided
into subnets allows it to be connected to the Internet with a single
shared network address.
The subnet mask is the part of the IP address that tells a network router
how to find the subnet that the data packet should be delivered to. Using
a subnet mask saves the router having to handle the entire 32-bit IP
address; it simply looks at the bits selected by the mask.
Switch - A switch is a network device that connects network segments
together, and which selects a path for sending a unit of data to its next
destination. In general, a switch is a simpler and faster mechanism than
a router, which requires knowledge about the network and how to
determine the route. Some switches include the router function. See also
Router.
TCP (Transmission Control Protocol) - TCP is used along with the
Internet Protocol (IP) to transmit data as packets between computers
over the network. While IP takes care of the actual packet delivery, TCP
keeps track of the individual packets that the communication (e.g.
requested a web page file) is divided into, and, when all packets have
arrived at their destination, it reassembles them to re-form the complete
file.
TCP is a connection-oriented protocol, which means that a connection is
established between the two end-points and is maintained until the data
has been successfully exchanged between the communicating
applications.
Telnet - Telnet is a simple method with which to access another
network device, e.g. a computer. The HTTP protocol and the FTP
protocols allow you to request specific files from remote computers, but
do not allow you logon as a user of that computer. With Telnet, you log
on as a regular user with whatever privileges you may have been
granted for specific applications and data residing on that computer.
TVL (TV Lines) - A method of defining resolutions in analog video.
UDP (User Datagram Protocol) - UDP is a communications protocol
that offers limited service for exchanging data in a network that uses
the Internet Protocol (IP). UDP is an alternative to the Transmission
Control Protocol (TCP). The advantage of UDP is that it is not required to
deliver all data and may drop network packets when there is, e.g.
network congestion. This is suitable for live video, as there is no point in
re-transmitting old information that will not be displayed anyway.
Unicast - Communication between a single sender and a single receiver
over a network. A new connection is established for each new user.
URL (Uniform Resource Locator) - An "address" on the network.
USB - (Universal Serial Bus) A plug-and-play interface between a
computer and peripheral devices, e.g. scanners, printers, etc.
Varifocal lens - A varifocal lens provides a wide range of focal lengths,
as opposed to a lens with a fixed focal length, which only provides one.
VAPIX - AXIS VAPIX is considered to be the global application
programming interface (API) standard, in the rapidly growing field of
Network Video based on IP.
VPN (Virtual Private Network) - This creates a secure "tunnel"
between the points within the VPN. Only devices with the correct "key"
will be able to work within the VPN. The VPN network can be within a
company LAN (Local Area Network), but different sites can also be
connected over the Internet in a secure way. One common use for VPN
is for connecting a remote computer to the corporate network, via e.g. a
direct phone line or via the Internet.
VOP (Video Object Plane) - A VOP is an image frame in an MPEG-4
video stream. There are several types of VOP:
- An I-VOP is complete image frame.
- A P-VOP codes the differences between images, as long as it is more
efficient to do so. Otherwise it codes the whole image, which may also
be a completely new image.