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White Paper V600
20 August 2005
Figure 1 shows the functional components of a
PSS client. The functional components can be
divided into control, scene description, media
codecs and the transport of media and control
data. TS 26.233 “Transparent end-to end packet
switched streaming service (PSS); General descrip-
tion” defines the simple and extended PSS.
The control-related elements are session establish-
ment, capability exchange and session control.
• Session establishment refers to methods of
invoking a PSS session from a browser or
directly by entering an URL in the user interface
of the terminal.
• Capability exchange enables choice or adapta-
tion of media streams depending on different
terminal capabilities.
• Session control deals with the set-up of the
individual media streams between a PSS client
and one or several PSS servers. It also enables
control of the individual media streams by the
user. It may involve VCR-like presentation con-
trol functions like start, pause, fast forward and
stop when presenting media.
The scene description consists of spatial layout
and a description of the temporal relation between
different media that is included in the media pres-
entation. The first gives the layout of different
media components on the screen and the latter
controls the synchronization of the different media.
The PSS includes media codecs for video, still images, vector graphics, text, audio, and speech.
Figure 2 describes the media transport protocol stack. Transport of media and control data consists of the
encapsulation of the coded media and control data in a transport protocol. This is shown in figure 1 as the
“packet based network interface” and displayed in more detail in the protocol stack of figure 2.
Figure 2. Overview of the protocol stack
Video
Audio
Speech
Scene description
Presentation description
Still images
Bitmap graphics
Vector graphics
Text
Presentation
description
Payload formats
RTP
HTTP
RTSP
UDP
TCP UDP
IP