Digital video is a large subject that draws upon an equally large number of technologies. Fortunately, every process can be broken down into smaller steps, each of which is relatively easy to follow. The main difﬁ culty in the study is to appreciate where the small steps ﬁ t into the overall picture. The purpose of this chapter is to summarise the subject and to point out how those technologies are used, without attempting any explanations beyond basics. More comprehensive explanations can be found in the later chapters that are identiﬁ ed here.