Page 51 - Video Coding for Mobile Communications Efficiency, Complexity, and Resilience

28 Chapter 2. Video Coding: Fundamentals

(a) FOREMAN (b) AKIYO (c) TABLE TENNIS
Figure 2.7: Three test sequences

spread of data properties. The Moving Picture Experts Group (MPEG) estab-
lished a library of CCIR-601 test sequences divided into ve classes: class A
(low spatial detail and low amount of motion), class B (medium spatial detail
and low amount of motion or vice versa), class C (high spatial detail and
medium amount of motion, or vice versa), class D (stereoscopic), and class E
(hybrid of natural and synthetic content) [27]. The rst three classes are more
relevant to the work carried out in this book. Thus, the book uses three test
sequences: AKIYO,FOREMAN, and TABLE TENNIS, where each sequence is a rep-
resentative of one of the three relevant classes, A, B, and C, respectively. The
three sequences are at QSIF resolution and include 300 frames each. This res-
olution is typical of the sequences used in very-low-bit-rate applications. Both
AKIYO and TABLE TENNIS have luma components of 176 × 120 and a frame rate
of 30 frames=s, whereas FOREMAN has a luma component of 176 × 144 and a
frame rate of 25frames=s. Figure 2.7 shows the luma component of the rst
frame of each of the three test sequences.

2.6 Intraframe Coding

Intraframe coding refers to video coding techniques that achieve compression
by exploiting (reducing) the high spatial correlation between neighboring pels
within a video frame. Such techniques are also known as spatial redundancy
reduction techniques or still-image coding techniques.

2.6.1 Predictive Coding

Predictive coding was originally proposed by Cutler in 1952 [28]. In this
method, a number of previously coded pels are used to form a prediction of
the current pel. The di)erence between the pel and its prediction forms the
signal to be coded. Obviously, the better the prediction, the smaller the error