This Recommendation | International Standard specifies the system layer of the coding. It was developed principally to support the combination of the video and audio coding methods defined in Parts 2 and 3 of ISO/IEC 13818. The system layer supports five basic functions: 1) the synchronization of multiple compressed streams on decoding; 2) the interleaving of multiple compressed streams into a single stream; 3) the initialization of buffering for decoding start up; 4) continuous buffer management; and 5) time identification.