Game Development Reference
In-Depth Information
Chapter 2
Video Coding Basic Principle
This chapter gives an overview of basic video coding principles. It consists of five
parts. The first part provides the concept of color spaces and the conversion among
typical color spaces. In the second part, we describe the typical video formats used in
video coding. The third part introduces the basic coding principle and the component
of coding tools. The fourth part talks about the quality assessment of the videos briefly,
and the last part concludes this chapter.
2.1 Color Spaces
2.1.1 Color Perception
As we know, light is characterized by its wavelength (or frequency) and its inten-
sity, and color is a visual perception of the light arriving at the photoreceptor cells
in the retina of human eyes. The ability of the human eyes to distinguish colors is
due to the varying sensitivity of different cells to the light of different wavelengths,
and there are two kinds of photoreceptor cells in the human eyes, called rods and
cones, as shown in Fig.
2.1
. Rods are extremely sensitive to the light intensity but
insensitive to the colors, while cones are sensitive to the colors and insensitive to
the light intensity. At very low light levels, visual experience solely depends on
the rods. For example, we cannot recognize the colors correctly in the dark rooms,
because only one type of photoreceptor cell is active. For color perception, the retina
contains three types of cones. As shown in Fig.
2.2
, they can sense light with the spec-
tral sensitivity peaks in short (S, 420-440nm), middle (M, 530-540nm), and long
(L, 560-580nm)wavelengths corresponding to blue, green, and red light respectively,
also called as blue, green, and red cones respectively. These three kinds of cones com-
prise a trichromatic color vision system. In the trichromatic color vision system, any
color perceived by the human eyes is a weighted sum of stimulus from the three
