TITRE Adaptive Packet Video Streaming Over IP Networks - LaBRI

Figure 5-19: MPEG-4 video packet loss ratio vs. network load with IP Best Effort
Figure 5-20 shows the percentage of packets losses when the amount of background traffic is
about 80% (6.5 Mbit/s) of the bandwidth. This leads to some losses essentially at time t=30s i.e.
when the video server sends at its peak rate. The majority of the losses are concentrated within the
base layer stream. This provides a degradation of the video quality at the client. Moreover, the
receiver can’t decode properly the other elementary video streams without the good reception of
the base layer. Loss increases dramatically when the network load increases (Figure 5-21).
The high losses of the base layer are due to its highest requirement of bandwidth. We can
compare it with a MPEG-2 video stream where I pictures are bigger than P and B pictures.
However, they are much more important. In this case, I packet’s losses must be lower than the
other packets types losses. When talking about MPEG-4, the base layer stream must have a low
packet loss when the enhanced layers streams 1 and 2 must have a respectively increasing drop
probability.
1
MPEG-4 Based Layer Stream -AF11
MPEG-4 Enhanced Layer Stream 1 -AF12
MPEG-4 Enhanced Layer Stream 2 -AF13
Packet Drop
0.8
% Packets Dropped (100%)
0.6
0.4
0.2
0
0 10 20 30 40 50 60
Time (s)
Figure 5-20: Packet drops in Best Effort scenario. - network load 80% -
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