In this chapter we describe the six syntactical layers of the MPEG-1 video bitstream the video sequence, group of pictures, picture, slice, macroblock, and block layers. This chapter deals primarily with the mechanics of moving or translating parameter values (data elements, in MPEG parlance) to and from the coded bitstream. How the parameters are actually used in quantization, coding, and reconstruction of the pels is described elsewhere.

As in preceding chapters, we present the syntax for each layer in two different ways, pseudocode and flowcharts. The pseudocode uses essentially the same formatting conventions as in the standard, but with comments added to explain each step. The flowcharts present the same material graphically. Chapter 6 provides a tutorial covering the pseudocode and flowchart conventions used in this chapter.

Although we have made every effort to provide a correct description of MPEG, any serious implementer should work from the actual standards documents. These are the only official sources for information about MPEG. Since these documents evolve over time, an official copy of the standard should be ordered from your national standards body or the ISO Information Technology Task Force (ITTF) in order to obtain the latest version and errata sheets.