TABLE OF CONTENTS Sound recording and the movie camera were among the greatest inventions of Thomas Edison. They were later united when "talkies" were developed, and they are still used together in video recordings. This unification is one reason for the popularity of movies and video. With the rapid advances in computers in the 1980s and 1990s came multimedia applications, where pictures and sound are combined in the same file. Such files tend to be large, which is why compressing them became a natural application.
This chapter starts with basic discussions of analog and digital video, continues with the principles of video compression, and concludes with a description of several compression methods designed specifically for video, namely MPEG-1, MPEG-4, H.261 and H.264.
An analog video camera converts the image it "sees" through its lens to an electric voltage (a signal) that varies with time according to the intensity and color of the light emitted from the different image parts. Such a signal is called analog, because it is analogous (proportional) to the light intensity. The best way to understand this signal is to see how a television receiver responds to it.
From the Dictionary
Analog (adjective).
Being a mechanism that represents data by measurement of a continuously variable quantity (as electrical voltage).
A television receiver (traditionally a CRT, or cathode ray tube, Figure 6.1a), is a glass tube with a familiar shape. In the back it has an electron gun (the cathode) that emits a stream...
