IntroductionThe systems part of this Recommendation | International Standard addresses the combining of one or more elementarystreams of video and audio, as well as other data, into single or multiple streams which are suitable for storage ortransmission. Systems coding follows the syntactical and semantic rules imposed by this Specification and providesinformation to enable synchronized decoding of decoder buffers over a wide range of retrieval or receipt conditions.System coding shall be specified in two forms: the Transport Stream and the Program Stream. Each is optimized for adifferent set of applications. Both the Transport Stream and Program Stream defined in this Recommendation |International Standard provide coding syntax which is necessary and sufficient to synchronize the decoding andpresentation of the video and audio information, while ensuring that data buffers in the decoders do not overflow orunderflow. Information is coded in the syntax using time stamps concerning the decoding and presentation of codedaudio and visual data and time stamps concerning the delivery of the data stream itself. Both stream definitions arepacket-oriented multiplexes.The basic multiplexing approach for single video and audio elementary streams is illustrated in Figure Intro. 1. Thevideo and audio data is encoded as described in ITU-T Rec. H.262 | ISO/IEC 13818-2 and ISO/IEC 13818-3. Theresulting compressed elementary streams are packetized to produce PES packets. Information needed to use PESpackets independently of either Transport Streams or Program Streams may be added when PES packets are formed.This information is not needed and need not be added when PES packets are further combined with system levelinformation to form Transport Streams or Program Streams. This systems standard covers those processes to the rightof the vertical dashed line.