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AXIS 214 PTZ
MPEG-4 protocols and communication methods
To deliver live streaming video over IP networks, various combinations of transport protocols and broadcast
methods are employed.
•RTP (Realtime Transport Protocol) is a protocol that
allows programs to manage the real-time trans-
mission of multimedia data, via unicast
or multicast.
•RTSP (Real Time Streaming Protocol)
serves as a control protocol, to negotiate which transport pro-
tocol to use for the stream. RTSP is thus used by a viewing client
to start a unicast session, see
below.
•UDP (User Datagram Protocol) is a communications protocol that offers limited service for ex
chang-
ing 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.
•Unicasting is communication between a single sender and a single receiver over a netwo
rk. This
means that the video stream goes independently to each user, and each user gets their own stream. A
benefit of unicasting is that if one stream fails, it only affects one user.
•Multicast is bandwidth-conserving technology
that reduces bandwidth usage by simultaneously
delivering a single stream of information to multiple network users. This technology is used prima-
rily on delimited networks (intranets), as each user needs an uninterrupted
data flow and should not
rely on network routers.
How to stream MPEG-4
Deciding on the combination of protocols and methods to use depends on your viewing requirements, and
on the properties of your network. Setting the preferred method(s) is done in the control applet for AMC,
which is found in the Windows Control Panel. When this has been set, AMC will test all the selected
methods in the specified order, until the first functioning method is found.
RTP+RTSP
This method (actually RTP over UDP and RTSP
over TCP) should be your first consideration for live video,
especially when it is important to always have an up-to-date video stream, even if some images do get
dropped. This can be configured as multicast or unicast.
Multicasting provides the most efficient usage of bandwidth, especially when there are large numbers of
clients viewing simultan
eously. Note however, that a multicast broadcast cannot pass a network router
unless the router is configured to allow this. It is thus not possible to multicast over e.g. the Internet.
Unicasting should be used for video-on-demand broadcasting, so that
there is no video traffic on the
network until a client connects and requests the stream. However, as more and more unicast clients
connect, the traffic on the network will increase and may cause congestion. Although there is a maximum
of 20 unicast viewers, note that all multicast users combined count as 1 unicast viewer.
RTP/RTSP
This unicast method is RTP tunneled over RTSP. This can be used
to exploit the fact that it is relatively
simple to configure firewalls to allow RTSP traffic.
RTP/RTSP/HTTP or RTP/RTSP/HTTPS
These two methods can also be used to
traverse firewalls. Firewalls are commonly configured to allow the
HTTP protocol, thus allowing RTP to be tunneled.
AXIS Media Control
The recommended method of accessing live video (MPEG-4 and/or Motion JPEG) and audio from the AXIS
214 PTZ is to use the AXIS Media Control (AMC) in Microsoft Internet Explorer in Windows. This ActiveX
component is automatically installed on first use, after which it can be configured by opening the AMC
Control Panel applet from the Windows Control Panel. Alternatively, right-click the video image in Internet
Explorer.