TITRE Adaptive Packet Video Streaming Over IP Networks - LaBRI

4.2.3.1.2 Scenario 2
In this scenario, we demonstrate the effect of the unequal error protection (UEP) of our RTP
payload. The transmitted MPEG-4 scene is composed of a set of Audio Visual Objects (AVOs).
The first object (O1) is a 25-fps video stream composed of 3 hierarchical layers (Base Layer,
Enhancement Layer 1 and Enhancement Layer 2). The second object (O2) is also a 25-fps video
stream composed of one single layer. Finally, the last object (O3) is an AAC audio stream. The
instantaneous throughput of each object during one-minute is described as follows. The full
MPEG-4 scene has an average rate of 770 Kbits/s and a peak rate of 1460 Kbits/s. Assume that
the audio (O3) has the higher priority score than O2 which have a higher priority score than O1 in
the MPEG-4 scene. Diffserv marking uses this information and marks each object stream by a
Diffserv code point to reflect a particular Diffserv class of service (high drop, low drop, etc.).
When UEP is performed, it uses the priority value of each Access Unit. The higher priority
score corresponds to higher FEC protection as shown in Table 4-5.
AU types Object Type Priority
Base Layer, I-frame Video p=2
EL1 Layer, P-frame Video p=1
EL2 Layer, B-frame Video p=0
CELP Voice Sample Audio p=0
Table 4-5: MPEG-4 AVO priority
With respect to this error protection policy, the redundant data generates a global network
traffic overhead equal to 7.0 % of the total traffic (i.e., 12.5, 6.0, and 0.0 % for the objects O1, O2,
and O3 respectively).
4.2.3.2 Simulation Results
4.2.3.2.1 Result of scenario 1
Figure 4-18 illustrates the end-to-end transmission delay for each AU generated by the CELP
stream. This delay was calculated from the AU’s coding generation time (CTS) until the AU’s
decoder reception time. We note that in the Figure 4-18, our proposal provides a better end-to-end
delay transmission (means of 0.075s in our proposal compared to 0.175s of the IETF approach).
This is especially due to our RTP packetization process (i.e. multiplexing scheme), which takes only
80 ms while in the IETF approach RTP packetization takes 240 ms. Value calculated between the
coding generation time and the decoder reception Time.
88