MPEG System Basics
The implementation of an MPEG-2 decoder platform is accomplished by the integration of multiple functions. The audio and video decoders only provide for decompressing of their respective data. RF tuners and displays are not specified by MPEG at all. All the information required to successfully demultiplex and then decode on MPEG-2 Stream arrives in a single continuous stream of ones and zeros. The audio, video and other data is multiplexed together and needs to be separated and reassembled before being sent to the decoders and ultimately displayed on the user’s audio/video equipment. MPEG-2 Systems is the essential element in being able to separate the data and move it to the correct place for interpretation and use by the other components of the receiver platform. Along with audio and video, MPEG-2 Systems streams also carry data associated with a program or programs in a data stream. MPEG-2 Systems can be specified using two formats. Transport Stream is a syntax that provides the necessary formatting elements for broadcast applications such as cable, while Program Stream does the job for stored media applications such as DVD. This chapter will explain both formats, the elements that comprise the streams and how each provides the necessary information to ensure synchronized playback of an AV stream. It should be noted that MPEG-2 is the informal name for a specification developed and published jointly by both the ITU and ISO. Its formal designation is ITU-T Rec. H.222.0|ISO/IEC 13818-1.