TITRE Adaptive Packet Video Streaming Over IP Networks - LaBRI

The TCM algorithm is based on a token bucket model. The token bucket defines three states.
Thus, resulting marking can be done using the Olympic service (gold, silver, and bronze). The
marking is based on a Committed Information Rate (CIR) and two associated burst sizes, a
Committed Burst Size (CBS) and an Excess Burst Size (EBS). A packet is marked as gold if it
doesn’t exceed the CBS, silver is does exceed the CBS, but not the EBS, and silver otherwise.
It is clear that in case of video traffic, the above marker algorithms do not meet all the
requirement of the video stream, since the video can be composed of important data and less
important one. The above algorithms mark the video traffic according to the sending rate rather
than according to the relevance of the data. For this reason, it is necessary to develop a specific
marker for video stream in particular for MPEG-4 AVOs. We suggest that this marker will be
implemented in the video server because it is the only element which is aware of the relevance and
the importance of the streamed data. The next section presents our design philosophy of the
marking algorithm.
5.2 DVMA: An IP Diffserv Packet Video Marking Algorithm
In this section, we propose a novel marking algorithm for IP Diffserv that will manage
MPEG-4 video streams (see Figure 5-1). This algorithm can be implemented in the media server as
well as in the Diffserv router. We assume that the video packets are encapsulated on RTP/UDP/IP
and marked according to the algorithm described in Figure 5-1. Let us note that this algorithm is
static and depends largely of our assumptions that are explained in the following (further we
describe a generic marking algorithm). We note, that destination terminal (player) is able to specify
its QoS requirements since it is aware of its processing, communication and storage capabilities. It
is clear that in case of bi-directional real-time video applications such as videoconferencing, audio is
more significant than video (property 1). This property led us to distinguish between marking from
the audio and the video streams in Diffserv edge nodes.
if stream is “audio stream” then (application of property 2)
if coder rate is “low rate”
then DSCP=AF Low Drop Prec
//example AF11
if coder rate is “medium rate”
then DSCP=AF Medium Drop Prec
//example AF12
if coder rate is “high rate”
then DSCP=AF High Drop Prec
//example AF13
if stream is “video stream” (application of property 3)
if “base layer video stream”
(level 1 = mimimum QoS)
then DSCP = AF low Drop Prec
//example AF21
if “ enhanced layer video stream 1” (level 2 = medium QoS)
then DSCP = AF Medium Drop Prec
//example AF22
if “enhanced layer video stream 2” (level 3 = maximum QoS)
then DSCP = AF Medium Drop Prec
//example AF23
if stream is “objects descriptor, scene descriptor” (application of property 4 )
then DSCP = EF
//descriptions streams are significant, no loss
//it’s necessary that these streams will be available
//as soon as possible in MPEG-4 player to interpret
//correctly the scene
Figure 5-1: DVMA- IP Diffserv video marking algorithm
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