In the chapter, we compare the proposed method with the “Raster scan” and the
“Dispersed” macroblock assignments, both of them are the FMO mode included in the standard. The parameters of our experimental environment are set as follows:
z Test sequence: Foreman, Coastguard, Stefan z Group of Picture (GOP): I P P P P ……
z GOP size: 15 frames z Frame rate: 30 fps
z Frame format: QCIF (176 x 144 pixels) z SG number: 6 SGs
z Packet size: 16 bytes
z Overall bit rate: 340Kbps (Foreman), 360Kbps (Coastguard), 980Kbps (Stefan)
The video sequences are encoded and decoded using JM 12.1 [25] where the code of motion estimation is modified to support the proposed CME-AZB. In our experiments,
“Raster scan” and “Dispersed” are Equal Error Protection (EEP) with the same overall bit rate. We add the “Shih’s UEP method without CME” and “Shih’s UEP method with CME” for comparison Shih’s UEP method reorders the macroblocks according to their defined impact factors (IF) and then sequentially assign to six SGs of unequal size using dispersed and k-means cluster as described in Section 2.2. Channel rate allocation in Shih’s method is done simply by assign RS depend on number of frames and slices linear proportional to the important of slices. Table 4.1 summarizes the
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difference between Shih’s method and the proposed approach.
Shih’s UEP method Proposed UEP method Macroblock
Classification Scheme
Shih’s distortion estimation method
Use ROPE formula to calculate expect distortion and treated it as Impact Factor
Assign RS by UEP depend on number of frames and slices linear proportional to the important of slices
RD Optimized algorithm with Lagrange multiplier
Motion Estimation Add penalty on higher slice,
may increase bitrates CME-AZB
Table 4.1 Compare Proposed UEP with Shih’s UEP method
“Proposed UEP method without CME-AZB” and “Proposed UEP method with CME-AZB” are both implements in our experiments for comparison. The measured average PSNR results of Forman, Coastguard, and Stefan with packet loss rate 10%
and 20% are shown in Figure 4.1 (a)(b), Figure 4.2(a)(b), and Figure 4.3(a)(b), respectively. The efficiency of using packet loss rate 20% is better than that of using 10% because EEP can not handle high packet loss rate. We can see that Dispersed is better than Raster scan because error concealment is more efficient in Dispersed than Raster scan. Shih’s UEP method performs well than Raster Scan and Dispersed mode in all cases, showing that unequal protection can achieve a better result than EEP. We can see that the proposed UEP method without CME-AZB is better than Shih’s UEP method without CME, it showing that the proposed RD optimized rate distortion channel allocation can improve the quality indeed. The PSNR of Shih’s UEP with
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CME higher than that if CME is not used showing that CME-AZB will further improve CME method indeed. It is show that our proposed UEP without CME-AZB performs even better than Shih’s UEP with CME. That proves again the superiority of our RD optimized channel rate allocation algorithm. The proposed UEP with
(a)
(b)
Figure 4.1 The PSNR when packet loss rate reach (a) 10% (b) 20% in Foreman 17
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CME-AZB performs better than proposed UEP without CME-AZB, showing that CME-AZB did take effect in the experiments. Because there are no motion vectors in I frame, CME and CME-AZB can not be performed in I frame Thus CME and CME-AZB can not improve UEP method at I frame in a GOP as shown in each result.
(a)
(b)
Figure 4.2 The PSNR when packet loss rate reach (a) 10% (b) 20% in Coastguard 17
19 21 23 25 27 29 31 33 35 37
1 11 21 31 41 51 61 71 81 91 101
PSNR
Frame Number
11 16 21 26 31
1 11 21 31 41 51 61 71 81 91 101
PSNR
Frame Number
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Figure 4.4shows the PSNR result as a function of packet loss rates, ranging from 5%
to 25% for Foreman sequence. When the packet loss rate reaches 5%, EEP is better than UEP because the protection rate is high enough to handle most channel errors, but UEP would not be able to in the situation. With the increasing of packet loss rate, the efficiency of UEP is more obvious especially in Coastguard because UEP protect
(a)
(b)
Figure 4.3 The PSNR when packet loss rate reach (a) 10% (b) 20% in Stefan 13
18 23 28 33
1 11 21 31 41 51 61 71 81 91 101
PSNR
Frame Number
13 15 17 19 21 23 25 27 29 31
1 11 21 31 41 51 61 71 81 91 101
PSNR
Frame Number
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the important data with more RS code. When packet loss rate reach 25%, the measured PSNR of UEP is almost equal to EEP because the overall bit rate is not high enough to handle the high packet loss rate no matter wheatear UEP or EEP is used.
From the above figures, it is clear that our proposed method could maintain the quality.
Given the same SNR, different PHY modes tend to result in different packet loss rate.
We use SNR as the input and let encoder choose the best PHY mode according the algorithm present in section 3.3. The experiment results are shown in Figure 4.5 where the SNR is shows that the packet loss rates are around 5% to 25% when SNR between 5 to 30 dBi. We added two tests which are “Normal PHY mode” and
“Proposed PHY mode method” as Method 1 and Method 2 with our proposed UEP algorithm with CME-AZB. “Normal PHY mode” uses the fixed PHY mode 4 and
“Proposed PHY mode method” will use the proposed method select the best PHY mode according to it SNR. From the above figure, it shows that if it PHY mode is changed dynamically according to SNR, and then it will improve its video quality.
1 (a)
(b)
(c)
Figure 4.4 The average PSNR when packet loss rate equal to 5% ~ 25% in video stream (a) Foreman (b) Coastguard (c) Stefan
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1 (a)
(b)
(c)
Figure 4.5 The average PSNR according by SNR between 5% ~ 30% in video streams (a) Foreman (b) Coastguard (c) Stefan
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