TITRE Adaptive Packet Video Streaming Over IP Networks - LaBRI
TITRE Adaptive Packet Video Streaming Over IP Networks - LaBRI
TITRE Adaptive Packet Video Streaming Over IP Networks - LaBRI
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6.1.1.4 S<strong>IP</strong> Communication Model<br />
S<strong>IP</strong> is based on the request-response paradigm. To initiate a session, the UAC sends a request<br />
(called an INVITE) addressed to the person the caller want to talk to. The addresses are similar to<br />
mailto URL (sip:user@server). The message is not send directly to the called party but rather to the<br />
proxy. Then, the proxy delivers the message to the called party. The called party sends a response,<br />
accepting or rejecting the invitation, which is forwarded back to the caller in reverse order like<br />
undelivered mail in Internet.<br />
Figure 6-3: A S<strong>IP</strong> call-setup signaling<br />
Bellow is an example of S<strong>IP</strong> scenario:<br />
1 User A (a@caller.com) calls User B (b@example.com). User A send INVITE message to the<br />
proxy of example.com (INVITE sip: b@example.com), then the proxy of example.com tell<br />
User A, that it is trying to connect to b@example.com<br />
2 The proxy locates in which terminal (PC) the User B is logged currently. This task is<br />
performed by a REGISTER message send by User B when he turned on his S<strong>IP</strong> user agent<br />
client. This would allow that User B is actually at foo.example.com (sip: b@foo.example.com).<br />
The bindings registered are periodically refreshed.<br />
3 The proxy send INVITE message to UAC of User B (INVITE sip:b@foo.example.com), this<br />
later replies the proxy with ringing informational message. The proxy informs the caller that is<br />
ringing at User B.<br />
4 When B accepts the invitation an acknowledgement message (ACK) is sent, and the session is<br />
established, Media can then flow between User A and User B. Others ways, User B can rejects<br />
the invitation. Figure 6-3 shows an example of a basic configuration between 2 UAs using S<strong>IP</strong><br />
protocol.<br />
6.1.2 ISO/IEC 14496-6 (MPEG-4 DMIF)<br />
MPEG-4 DMIF is the control plane of MPEG-4 Delivery layer that allows applications to<br />
transparently access and view multimedia streams whether the source of the stream is located on an<br />
interactive remote end-system, the stream is available on broadcast media or is located on stored<br />
media [144].<br />
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