12
AXIS 231D+/232D+ - Video Streams
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 multi
media 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 alterna-
tive 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 for example,
network congestion. This is suitable for live video, as there is no point in re-transmit-
ting old information that will not be displayed anyway.
• Unicasting is communication between a single se
nder and a single receiver over a net-
work. This means that the video stream goes independently to e
ach 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 simul-
taneously delivering a single stream of information to mul
tiple network recipients. This
technology is used primarily on delimited networks (intranets), as each user needs an
uninterrupted data flow and should not rely on network routers.
