ABSTRACT
In this chapter, we discuss video transcoding at the transport level. For this purpose, we first introduce the basic concept of MPEG-2 [5-1], a system that has specified two stream forms: the transport stream (TS) and the program stream (PS), which are designed for different sets of applications. The functions of the transport and program streams include methods for multiplexing the elementary audio and video streams to a signal stream with time synchronization and other important information. We are therefore going to present the transcoding techniques that are used to perform the conversions between the twostreams. The transcoding between TS and PS has an important application, which can be applied to convert digital television (DTV) broadcasting’s audio and video bit streams into audio and video bit streams for digital video disc (DVD). An important technical issue for transcoding between PS and TS is the rate contro algorithm. Usually, for DVD applications, the video is encoded by variable bit rate (VBR), whereas for DTV applications, due to buffer requirements, the video should be encoded by constant bit rate (CBR). Finally, the technical details about CBR and VBR and transcoding algorithms for CBR to VBR will be introduced.
