Page 254 - Video Coding for Mobile Communications Efficiency, Complexity, and Resilience

Chapter 10

Error Concealment Using Motion

Field Interpolation

10.1 Overview

Chapter 9 discussed three categories of error-resilience techniques: forward,
postprocessing (or concealment), and interactive techniques. Almost all for-
ward techniques increase the bit rate because they workby adding redun-
dancy to the data, e.g., FEC. Some of them may also require modi$cations
to the encoder, e.g., layered coding, and others may not be suitable for some
applications, e.g., multiple description coding assumes several parallel chan-
nels between transmitter and receiver. Most interactive techniques depend on
a feedbackchannel between the encoder and decoder. Such a channel may
not be available in some applications, e.g., multipoint broadcasting. Most in-
teractive techniques will also introduce some delay and may, therefore, be
unsuitable for real-time applications like mobile video communication. On the
other hand, concealment techniques do not increase the bit rate, do not require
any modi$cations to the encoder, do not introduce any delay, and can be ap-
plied in almost any application. This makes them a very attractive choice for
mobile video communication, where bit rate and delay are very critical issues.
A very successful class of error concealment is temporal error conceal-
ment. Conventional temporal concealment techniques estimate one conceal-
ment displacement for the whole damaged blockand then use translational
displacement compensation to conceal the blockfrom a reference frame. The
main problem with such techniques is that incorrect estimation of the conceal-
ment displacement can lead to poor concealment of the whole or most of the
block.
This chapter describes the design of two novel temporal concealment tech-
niques. In the $rst technique, motion
eld interpolation (MFI) is used to
estimate one concealment displacement per pel of the damaged block. Each

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