User guide

4Sight 19
Administrator Guide
Version 3.1
Concepts
Streaming overview
The streaming process includes two parts: a client and a server. The server
sends an MPEG-4 formatted movie to a client over a network. Unlike the
progressive download or the simple file transfer (where the client waits for
the whole movie to be downloaded before playing anything), the server
does not send the movie as a whole, it divides it into small packets that can
easily be sent over a network. Then, the role of the receiver (the player or
the client) is to reassemble them and play the movie. The set of these
streamed small packets is called a stream.
The streaming protocol used is RTP (Real Time Protocol). RTP is usually
used to stream the packets in real time.
There are several ways to transmit RTP packets over the Internet:
• using TCP (Transmission Control Protocol)
• using UDP (User Datagram Protocol) or reliable UDP
• using HTTP tunneling (Hypertext Transfer Protocol).
The command protocol that allows the client to communicate with the
server is RTSP (Real-time Streaming Protocol). This protocol lets the
client decide what it wants to do (for example, begin the session, play the
clip, pause, or close).
The streams can be sent in two different ways:
• unicast - one to one (see “Unicast streaming” on page 20)
• or multicast - one to many (see “Multicast streaming” on page 21)