Page 138 - Video Coding for Mobile Communications Efficiency, Complexity, and Resilience

Section 4.6. Block-Matching Methods 115

Foreman @ 8.33 f.p.s.
36
With overlapping
No overlapping
34
PSNR Y (dB) 32
30
28

26
24
1 5 10 15 20 25 30 35 40 45 50
Frame
th
(a) Prediction quality (b) Original 15 frame at 8.33 f.p.s

(c) Compensated using BMA (29.35 dB) (d) Compensated using OMC (30.93 dB)

Figure 4.9: Comparison between OMC and BMA

4.6.7 Properties of Block-Motion Fields and Error Surfaces

This subsection presents some basic properties of the BMME algorithm when
applied to typical video sequences. These properties will be utilized and ref-
erenced in subsequent chapters of the book. All illustrations in this subsec-
tion were generated using a full-pel full-search block-matching algorithm with
16 × 16 blocks, ±15 pels maximum displacement, restricted motion vectors,
SAD as the BDM, and original reference frames.

Property 4.6.7.1 The distribution of the block motion eld is center-biased.
This means that smaller displacements are more probable and the motion vector
(0; 0) has the highest probability of occurrence. In other words, most blocks
are stationary or quasi-stationary. This property is illustrated in Figure 4.10(a)
for AKIYO at 30 frames=s (frame skip of 1). The property also holds true for