Page 278 - Video Coding for Mobile Communications Efficiency, Complexity, and Resilience

Section 10.6. Discussion 255

Table Tennis, M=10, QP=10, Skip=3 Table Tennis, M=10, QP=10, Macrblock error rate=20%
26 23.5
ZR-ZR ZR-ZR
MFI-BM MFI-BM
25 MFI-MH MFI-MH
23
24
23 22.5
PSNR Y (dB) 22 PSNR Y (dB) 22
21
20 21.5
19
21
18
17 20.5
10 20 30 40 50 1 2 3
4
Macroblock error rate (%) Skip
(a) Performance over a range of error rates (b) Performance over a range of frame skips
Figure 10.19: Multihypothesis temporal concealment for QSIF TABLE TENNIS with M =10 and
QP =10

over that of MFI-BM (Figure 10.20(d)). In particular note the left eye of
Foreman (to the right of the viewer) and the diagonal lines in the walls.

10.6 Discussion

Because of their simplicity, no added redundancy, and minimum delay, error
concealment techniques were identi$ed in this chapter as the most suitable
techniques for mobile video applications. Thus, it was decided to concentrate
on error concealment and in particular on temporal techniques.
Conventional temporal concealment techniques estimate one concealment
displacement for the whole damaged blockand then use translational dis-
placement compensation to conceal the blockfrom a reference frame. It was
realized, therefore, that wrong estimation of the concealment displacement can
lead to poor concealment of the entire or most of the block. To overcome
this drawback, a novel temporal concealment technique was designed. In this
technique, motion $eld interpolation (MFI) is used to estimate one conceal-
ment displacement per pel of the damaged block. Each pel is then concealed
individually. In this case, incorrect estimation of a concealment displacement
will a,ect only the corresponding pel rather than the entire block. The inherent
motion information recovery and the good motion compensation performance
of the MFI technique improve both stages of temporal concealment, i.e., esti-
mation and compensation.
To achieve a more robust performance, a second novel temporal conceal-
ment technique was also designed. In this technique, multihypothesis mo-
tion compensation (MHMC) is used to combine the MFI technique with a