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232 Chapter 10. Error Concealment Using Motion Field Interpolation

pel is then concealed individually. In this case, incorrect estimation of a con-
cealment displacement will a,ect only the corresponding pel. On a blocklevel,
this may a,ect few pels rather than the entire block. In the second technique,
multihypothesis motion compensation (MHMC) is used to combine the $rst
technique with a boundary matching (BM) temporal concealment technique
to obtain a more robust performance.
The chapter also investigates the performance of di,erent temporal error
concealment techniques when incorporated within a multiple-reference video
codec. In particular, the chapter $nds a combination of techniques that best
recovers the spatial-temporal components of a damaged multiple-reference
motion vector. In addition, the chapter describes the design of a novel
multihypothesis temporal concealment technique that can be used with
multiple-reference systems.
The rest of the chapter is organized as follows. Section 10.2 describes
the MFI temporal concealment technique, whereas Section 10.3 presents the
combined BM-MFI technique. Section 10.4 presents some simulation results.
Section 10.5 investigates the performance of temporal error concealment within
multiple-reference video codecs. It also describes the multihypothesis multiple-
reference temporal concealment technique. The chapter concludes with a dis-
cussion in Section 10.6.
Preliminary results of this chapter have appeared in Refs. 204, 205, 206,
207, and 208.

10.2 Temporal Error Concealment Using Motion
Field Interpolation (MFI)

10.2.1 Motivation
As described earlier, conventional temporal concealment techniques estimate
one concealment displacement for the whole damaged blockand then use
translational displacement compensation to conceal the blockfrom a reference
frame. As already discussed in Section 9.7.2, there are many cases where
conventional temporal concealment techniques can fail and the concealment
displacement can be incorrectly estimated. The main problem with such tech-
niques is that incorrect estimation of the concealment displacement can lead to
poor concealment of the entire or most of the block. This section describes a
new temporal error concealment technique. This technique estimates one con-
cealment displacement per pel of the damaged blockand then conceals each
pel individually. In this case, incorrect estimation of a concealment displace-
ment will a,ect only the corresponding pel. On a blocklevel, this may a,ect
few pels rather than the entire block.