Mpeg-4 Protocols And Communication Methods; How To Stream Mpeg-4; Axis Media Control - Axis 214 PTZ User Manual

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
transmission of multimedia data, via unicast or multicast.
• RTSP (Real Time Streaming Protocol) serves as a control protocol, to negotiate which transport
protocol 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
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.
• Unicasting is communication between a single sender and a single receiver over a network. 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 pri-
marily 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 the combination of protocols and methods to use depends on your viewing requirements, and on
the properties of your network. The available options in AMC are:
Unicast RTP
RTP over RTSP
RTP over RTSP over
HTTP
Multicast RTP
AMC negotiates with the camera to determine the transport protocol to use in the order listed above. This
order can be changed and the options disabled, to suit specific requirements.

AXIS Media Control

The recommended method of accessing live video 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.
This unicast method (RTP over UDP) should
be your first consideration for live unicast
video, especially when it is important to
always have an up-to-date video stream,
even if some images are dropped.
This unicast method (RTP tunneled over
RTSP) is useful as it is relatively simple to
configure firewalls to allow RTSP traffic.
This unicast method can be used to traverse
firewalls. Firewalls are commonly configured
to allow the HTTP protocol, thus allowing
RTP to be tunneled.
This method (RTP over UDP) should be used for live multicast video. The video stream is always
up-to-date, even if some images are dropped.
Multicasting provides the most efficient usage of bandwidth when there are large numbers of cli-
ents viewing simultaneously. A multicast broadcast cannot however, pass a network router unless
the router is configured to allow this. It is not possible to multicast over the Internet, for example.
Note also that all multicast viewers count as one unicast viewer in the maximum total of 10
simultaneous connections.
Unicasting is used for video streaming, so that there is
no video traffic on the network until a client connects
and requests the stream.
Note that there are a maximum of 20 simultaneous
unicast connections.
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