Page 12 - Video Coding for Mobile Communications Efficiency, Complexity, and Resilience

Preface xv

tracking algorithm. The chapter then assesses the suitability of warping-based
methods for mobile video communications. In particular, the chapter compares
the e"ciency and complexity of such methods to those of block-matching
methods.
Chapter 6 investigates the performance of another advanced motion-
estimation method, called multiple-reference motion-compensated prediction.
The chapter starts by brie2y reviewing multiple-reference motion estimation
methods. It then concentrates on the long-term memory motion-compensated
prediction technique. The chapter investigates the prediction gains and the cod-
ing e"ciency of this technique at very low bit rates. The primary aim is to de-
cide if the added complexity, increased motion overhead, and increased mem-
ory requirements of this technique are justi,able at such bit rates. The chapter
also investigates the properties of multiple-reference block-motion ,elds and
compares them to those of single-reference ,elds.
Part III of the book considers the challenge of reduced computational com-
plexity. It contains two chapters. Chapter 7 reviews reduced-complexity motion
estimation techniques. The chapter uses implementation examples and pro,ling
results to highlight the need for reduced-complexity motion estimation. It then
reviews some of the main reduced-complexity block-matching motion estima-
tion techniques. The chapter then presents the results of a study comparing
the di(erent techniques.
Chapter 8 gives an example of the development of a novel reduced-
complexity motion estimation technique. The technique is called the simplex
minimization search. The development process is described in detail, and the
technique is then tested within an isolated test environment, a block-based
H.263-like codec, and an object-based MPEG-4 codec. In an attempt to re-
duce the complexity of multiple-reference motion estimation (investigated in
Chapter 6), the chapter extends the simplex minimization search technique to
the multiple-reference case. The chapter presents three di(erent extensions (or
algorithms) representing di(erent degrees of compromise between prediction
quality and computational complexity.
Part IV concentrates on error resilience. It contains two chapters. Chapter 9
reviews error resilience video coding techniques. The chapter considers the
types of errors that can a(ect a video bitstream and examines their impact on
decoded video. It then describes a number of error detection and error control
techniques. Particular emphasis is given to standard error-resilience techniques
included in the recent H.263+, H.263++, and MPEG-4 standards.
Chapter 10 gives examples of the development of error-resilience tech-
niques. The chapter presents two temporal error concealment techniques. The
,rst technique is based on motion ,eld interpolation, whereas the second
technique uses multihypothesis motion compensation to combine motion ,eld
interpolation with a boundary-matching technique. The techniques are then