DIGITAL TELEVISION 16.9.1 Introduction Up to this point in the chapter we have covered the baseband TV signal and radio relaying of that signal via LOS microwave and satellite, where both are analog systems using frequency modulation. A "raw" TV video signal is naturally analog. Now convert a TV signal to a digital format. Let's assume it is PCM (Chapter 6) with those three steps required to develop a digital PCM signal from an analog counterpart. We will remember that those steps are sampling, quantization, and coding. The bit rate of such a digital signal will be on the order of 80-160 Mbps. If we were to assume one bit per hertz of bandwidth, the signal would require in the range of 80 to 160 MHz for just one TV channel! This is a viable alternative on extremely wideband fiber-optic systems. However, for narrower bandwidth systems, such as radio and coaxial cable, compression techniques are necessary. Television, by its very nature, is highly redundant. What we mean here is that we are repeating much of the same information over and over again. Thus a TV signal is a natural candidate for digital signal processing to remove much of the redundancy, with the potential to greatly reduce the required bit rate after compression. In this section we will discuss several digitizing techniques for TV video and pro- vide an overview of some bit rate reduction methods including a brief introduction to a derivative of MPEG-2.7 Section 16.10 reviews several approaches to the development of a conference television signal. 16.9.2 Basic Digital Television 16.9.2.1 Two Coding Schemes. There are two distinct digital coding methods for color television: component and composite coding. For our discussion here, there are four components that make up a color video signal. These are R for red, G for green, B for blue, and Y for luminance. The output signals of a TV camera are converted by a linear matrix into luminance (Y) and two color difference signals R-Y and B-Y. With the component method of transmission, these signals are indiv