TITRE Adaptive Packet Video Streaming Over IP Networks - LaBRI

Packet Transmission Delay (s)
0.11
0.1
0.09
0.08
0.07
0.06
0.05
0.04
0.03
Rate Controlled Audio
AUDIO
0.02
0 20 40 60 80 100 120 140
Simulation Time (s)
Scenario D
Figure 4-37: End-to-end packet transmission delay
4.3.3.2.2 User Perceived Quality
Peak Signal to Noise Ratio (PSNR) is an indicator of picture quality that is derived from the
root mean squared error. The PSNR for a degraded N1 x N2 8-bit image f’ from the original image
f is computed by the formula in Eq. 12:
255
PSNR = 20log10
(Eq. 12)
N1−1
N2−1
1
2
∑∑ [ f ( x,
y)
− f '(
x,
y)
]
N N
1
2 x=
0
y=
0
In order the compute PSNR value, we should rebuild the received scene. By using ns2 trace
file, we create the received MPEG-4 scene. The measured PSNR indicates the difference between
the original and the received video sequence. Figure 4-38 shows comparison between the original
and the received scene quality for scenarios (A, B, C, and D). As expected, and since there was no
loss in scenario A and B, the received quality is the same as the original quality. In Scenario C and
D, the degradation of the received quality is due to our adaptation mechanism which only sends
pertinent object to the client. This PSNR measurement does not reflect the meaning of what the
client received. Because in our case, the logo object is basically not send. This affects the PSNR
value but for the end user it does not have any importance (in our assumption). Figure 4-23
presents some snapshot of the received video in scenario D.
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