ISO/IEC 11172, the document describing MPEG-1, currently contains five parts. Part 1 covers the MPEG system layer, Part 2 describes MPEG video, and Part 3 specifies MPEG audio. Part 4 is on compliance testing, and Part 5 is a software reference model for MPEG-1.

Although the main topic of this book is MPEG video, MPEG audio and MPEG systems are also crucial parts of a complete MPEG implementation. A video bitstream is fully decodable, but, by itself, is an incomplete specification. The MPEG system layer contains control information that enables parsing and precise control of playback of the bitstream. Furthermore, a video stream without audio has only limited use.

This chapter presents an overview of all three parts: systems, audio, and video. As an aid for people who have access to the official MPEG-1 video standard, we sometimes reference a particular clause in that document (clause is standardeze for section). These references have the format "IS[w:x.y.z]", where IS refers to ISO/IEC 11172, w is the part number (systems, video, audio, etc.) and x.y.z is the clause or sub-clause number. If w is 2, it may be omitted. Thus, IS[2:2.3] and IS[2.3] both refer to subclause 2.3 of the video part.