MPEG is a standard which defines data formats for coded (compressed) audio, video, and their combination. The Systems part of this work, which is Part 1, defines the coding and related requirements for providing the combination of audio and video, including key system- level functions. These functions include synchronization of audio and video, multiplexing, clock recovery, guaranteed buffer behavior, program time identification, and many other system-level functions which are required in practice and which are not part of the compression coding of audio and video. MPEG-2 formally known as ISO 13818, and MPEG-2 Systems is ISO 13818-1. Currently MPEG-2 has the status of a Committee Draft, meaning that it has been published for review by participating national bodies, as part of the procedure for becoming an official International Standard.