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 six 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;5) time identification;6) multiplexing and signalling of various components in a system stream.An ITU-T Rec. H.222.0 / ISO/IEC 13818-1 multiplexed bit stream is either