4 Squeezing through the pipe: digital compression 4.1 Introduction Around the world the use of digital compression is an essential characteristic of not only of satellite newsgathering itself, but also of the whole newsgathering process, so in this chapter we will look at types of compression used for both video and audio. It should also be made clear at this point that we will primarily be dealing with `standard definition' (SD) television ­ the TV service that most countries utilize. Modern `high-definition' (HD) television is spreading from its roots in Japan and the US to other parts of the world, and we will look at its use in SNG later in this chapter.