Chapter 1 VIDEO FORMATION, PERCEPTION, AND REPRESENTATION

In this rst chapter, we describe what is a video signal, how is it captured and perceived, how is it stored/transmitted, and what are the important parameters that determine the quality and bandwidth (which in turn determines the data rate) of a video signal. We rst present the underlying physics for color perception and specication (Sec. 1.1). We then describe the principles and typical devices for video capture and display (Sec. 1.2). As will be seen, analog videos are cap-tured/stored/transmitted in a raster scan format, using either progressive or in-terlaced scans. As an example, we review the analog color television (TV) system (Sec. 1.4), and give insights as to how are certain critical parameters, such as frame rate and line rate, chosen, what is the spectral content of a color TV signal, and how can dierent components of the signal be multiplexed into a composite signal. Fi-nally, Section 1.5 introduces the ITU-R BT.601 video format (formerly CCIR601), the digitized version of the analog color TV signal. We present some of the consider-ations that have gone into the selection of various digitization parameters. We also describe several other digital video formats, including high-denition TV (HDTV). The compression standards developed for dierent applications and their associated video formats are summarized. The purpose of this chapter is to give the readers background knowledge about analog and digital video, and to provide insights to common video system design problems. As such, the presentation is intentionally made more qualitative than quantitative. In later chapters, we will come back to certain problems mentioned in this chapter and provide more rigorous descriptions/solutions. 1.1 Color Perception and Specication A video signal is a sequence of two dimensional (2D) images projected from a dynamic three dimensional (3D) scene onto the image plane of a video camera. The 1 2 Video Formation, Perception, and Representation Chapter 1 color value at any point in a video frame records the emitted or re ected light at a particular 3D point in the observed scene. To understand what does the color value mean physically, we review in this section basics of light physics and describe the attributes that characterize light and its color. We will also describe the principle of human color perception and dierent ways to specify a color signal