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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two H.323 endpoints or between an endpoint and the GK. H.225 specifies the<br />
mandatory Q.931 messages that are used for call signaling. Q.931 is actually an ISDNrelated<br />
protocol used to set up and clear calls. A Q.931 packet may contain a number<br />
of parameters known as information elements. For example, a Q.931 packet may<br />
contain a user information element. H.323 specifies that the user information element<br />
must contain an H.225 message. All the H.323 parameters are coded in user<br />
information element of Q.931 messages<br />
• H.245 Control Signaling: it is used to exchange end-to-end control messages<br />
governing the operation of the H.323 endpoint. These control messages carry<br />
information related to the following: capabilities exchange, opening and closing of<br />
logical channels used to carry media streams, flow-control messages and general<br />
commands and indications.<br />
• T.120 Data interoperability: T.120 is a series of multimedia communications<br />
protocols and is the default basis of data interoperability between an H.323 terminal<br />
and other terminals.<br />
3.2.5.2.2 IETF Protocols Suite<br />
The IETF has defined a set of protocol suitable for packet video application. The latest one is<br />
S<strong>IP</strong> (Session Initiation Protocol) that regroup the majority of others protocols. S<strong>IP</strong> is an<br />
application-layer control and signaling protocol for creating, modifying and terminating sessions<br />
with one or more participants. These sessions include <strong>IP</strong> multimedia conferences, <strong>IP</strong> telephony<br />
calls and multimedia distribution [140]. S<strong>IP</strong> has been approved in early 1999 as an official standard<br />
by the IETF for signaling communications services on the Internet. S<strong>IP</strong> can be used to initiate<br />
sessions as well as invite members to sessions. The S<strong>IP</strong> architecture includes the following<br />
protocols:<br />
• RTP (Real-Time Transport Protocol) for transporting real time audio, video and data<br />
[110], and RTCP (Real-Time Transport Control Protocol) is the control protocol for<br />
RTP, and provides mechanisms for data distribution monitoring, cross media<br />
synchronization, and sender identification. The sender transmits a multimedia data<br />
stream by using RTP packets. The receiver periodically sends RTCP packets that<br />
contain information about the received RTP packets. The information includes<br />
feedback and statistics such as the highest sequence number received, inter-arrival<br />
jitter, or packet loss rate.<br />
• RTSP (Real-Time <strong>Streaming</strong> Protocol) for setting up and controlling on-demand<br />
media streams [145]. RTSP is used for initiating and controlling delivery of stored and<br />
live multimedia content to both unicast and multicast destinations. RTSP borrows<br />
time concept from MPEG-2 DSM-CC, but unlike DSM-CC, it does not depend on an<br />
entire set of supporting protocols. RTSP is transport-independent, and can use either<br />
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